[page 39↓]

5  Results

5.1 Pre-weaning growth performance of lambs

In the analysis of variance the main effects of genotype, year, sex and the interaction effect of genotype and year were considered as presented in Table 5. The model explains 0.46 - 0.63 of the variation. The coefficient of variation was about 15% for estimated live body weight and 19 - 22 % for estimated ADG.

Table 5: Results of ANOVA for birth weight and pre-weaning growth of lambs

   

Body weight

Average daily gain

Effect

DF

Birth weight

Day 30

Day 60

Day 90

0 - 30 days

30 - 60 days

60 - 90 days

0 - 90 days

Genotype

2

***

***

***

***

***

***

***

***

Year

1

ns

**

***

***

**

***

***

***

Sex

1

*

*

**

***

ns

**

***

***

Birth month

1

ns

       

Gen x Year

2

ns

Ns

ns

**

ns

ns

***

**

R-SQ:

 

0.61

0.57

0.58

0.63

0.46

0.53

0.55

0.61

CV (%):

 

13.70

14.6

15.2

14.5

19.3

20.5

22.0

16.2

*** p≤0.001; ** p≤0.01;* p≤0.05; ns for not significant; DF Degrees of freedom

The effect of genotype and sex on birth weight was significant. There was also a significant (p 0.001) difference in the birth weight of the crossbred lambs. There was a significant effect of genotype, year and sex on live body weight of lambs at all three ages considered. The interaction effect of year and genotype was only significant at 90d of age. The effect of genotype and year on ADG was significant over the whole 90d period and over the three phases considered. The effect of sex on ADG was only significant over the last two phases (30 - 60d and 60 - 90d) of pre-weaning growth. The interaction effect of genotype and year on ADG was only significant during the last (60 - 90d) phase of pre-weaning growth.

Table 6: Effects of genotype and sex on birth weight and pre-weaning live weight of lambs, , LSQ-means ± se

  

Live weight (kg)

 
 

Birth weight, kg

Day 30

Day 60

Day 90

n

Genotype

     

Cameroon

2.3a ±0.10

6.6a ±0.34

10.8a ±0.57

15.1a ±0.74

19

C1

3.9b ±0.11

10.8b ±0.21

17.0b ±0.35

23.1b ±0.46

51

C2

3.4c ±0.10

10.8b ±0.22

17.8b ±0.37

24.6b ±0.48

47

Sex

     

Male

3.5a ±0.17

9.7a ±0.22

16.0a ±0.37

22.1a ±0.47

50

Female

3.3b ±0.11

9.1a ±0.20

14.5a ±0.33

19.8b ±0.43

67

Different letters within columns indicate significant differences p≤0.05


[page 40↓]

Least Squares Means and standard errors of estimated live body weight at 30, 60 and 90 days of age and of estimated ADG from 0 - 30, 30 - 60 and 60 - 90 days are presented in Table 6 and Table 7, respectively. At 30, 60 and 90 days of age, the C1 and C2 crossbred lambs weighed significantly heavier than the Cameroon. The difference in estimated weight was not significant between the C1 and C2 crossbred lambs although the latter recorded heavier weights.

Male lambs weighed more than female ones during the period considered, however, a significant difference in estimated live weight was only recorded at 90 days of age.

Table 7: Effects of genotype and sex on pre-weaning average daily gain of lambs, LSQ-means ± se

 

Average daily gain (g)

 
 

0 - 30 days

30 – 60 days

60 - 90 days

n

Genotype

    

Cameroon

142.8a ±9.93

142.1a ±9.77

142.7a ±9.97

19

C1

230.3b ±6.13

208.9b ±6.03

200.8b ±6.15

51

C2

245.1b ±6.47

235.6b ±6.36

226.3b ±6.49

47

Sex

    

Male

212.8a ±6.33

208.7a ±6.23

205.0a ±6.35a

50

Female

199.4a ±5.75

182.4b ±5.66

174.8b ±5.77b

67

Different letters within columns indicate significant differences p≤0.05

The C1 and C2 crossbred lambs recorded significantly higher ADG (Average Daily Gain) than the Cameroon at 30, 60 and 90 days of age. The difference between the C1 and the C2 crossbred lambs was not significant but the C2 had higher means than the C1 from 0 - 30, 30 - 60 and 60 - 90 days.

The Average Daily Gain for the C1 and C2 crossbred lambs exhibited a declining trend from 0 - 30, 30 - 60 and 60 - 90 days whereas that of the Cameroon remained almost unchanged during the same period.

Male lambs gained more than female ones during the period considered, however, a significant difference in estimated ADG was only recorded from 60 - 90 days. As expected, both males and females exhibited a declining trend for Least Square Means of estimated ADG from 0 - 30, 30 - 60 and 60 - 90 days.

5.2 Milk yield performance of Cameroon and C1 ewes using the suckling method

The milk yield performance of the Cameroon and C1 (Cameroon X Mutton) ewes from 1 - 9 weeks of lactation are presented in Table 8. Milk recording was done using the indirect suckling method in which the lambs were weighed before and after suckling. The model explains 0.82 of the variation over the whole experimental period of 9 weeks. It explains 0.66 - 0.67 of variation during the first three (3) weeks of lactation. Thereafter up to Week 9, the model explains only 0.22 - 0.40 of the variation. During Weeks 7 and 9, the coefficient of determination tended to be stable at 0.39 and 0.40. Thus after the third week of lactation, the model could not explain most of the variation.

The coefficient of variation was about 22% over the whole experimental period of 9 weeks. During the first three (3) weeks, the coefficient of variation was 22 - 23%, thereafter rising to 43 - 48% up to week 9. Mean variation increased considerably after the third week of lactation.


[page 41↓]

Table 8: Results of ANOVA for milk yield performance of ewes

 

Week

 
 

1

3

5

7

9

Total

Genotype

***

***

***

**

**

***

R-SQ

0.66

0.67

0.22

0.39

0.40

0.82

CV(%)

21.78

23.35

43.00

46.52

47.90

21.52

*** p≤0.001; ** p≤0.01;* p≤0.05; ns for not significant

The significant difference in milk yield performance between the Cameroon and the C1 (Cameroon X Mutton) ewes was very high during the first three weeks. Milk yield performance of the ewes was highly significantly affected by genotype over the whole experimental period up to Week 9, during Weeks 1 and 3 and during Week 5. During Weeks 7 and 9, the effect of genotype was very significant (p 0.01).

The means and standard errors of the milk yield performance of the Cameroon and the C1 (Cameroon X Mutton) ewes are presented in Table 9. During the first three (3) weeks of lactation, the C1 ewes yielded about two times more milk than the Cameroon. Thereafter up to Week 9, the C1 yielded three times more milk than the Cameroon apparently due to an abrupt fall in the milk yield performance of the latter.

Table 9: Influence of genotype on milk yield performance of ewes during 9 weeks of lactation, means ± se

 

Week

 

1

 

3

 

5

 

7

 

9

  

Total

 

n

M ±se, g

n

m ±se, g

n

M ±se, g

n

m ±se, g

n

m ±se, g

n

m ±se, kg

Genotype

            

Cameroon

5

820a ±86

7

771a ±118

7

514a ±67

6

433a ±117

7

457a ±71

8

40.95a ±3.64

C1

8

1450b ±113

9

1777b ±81

9

1689b ±175

9

1322b ±163

8

1400b ±159

9

107.57b ±6.77

Different letters within columns indicate significant differences p≤0.05

In general, the means thus reflect the superior milk yield performance of the C1 ewes compared with that of the pure Cameroon during the lactation period from 1 - 9 weeks.

Figure 1 shows the regression of the milk yield performance of the Cameroon and the C1 (Cameroon x Mutton) ewes during 1 - 9 weeks of lactation. The regression of milk yield over this period shows a very high intercept of 1667g per ewe per day for the C1 crossbred ewes compared with 865g for the Cameroon. This constituted about two times more milk yield performance by the C1 ewes compared with that of the pure Cameroon.

The rate of change, b, for the C1 ewes was negative (-28g per week) and lower than that of the Cameroon (-53 g per week). The milk yield performance of the Cameroon ewes was therefore less persistent than that of the C1 (Cameroon X Mutton) ewes during 1 - 9 weeks of lactation.


[page 42↓]

Fig. 1: Milk performance of Cameroon and C1 ewes during 9 weeks of lactation

5.3 Comparative post-weaning growth performance of lambs of different genotypes

5.3.1 Influence of different feeding levels on performance

The analysis of variance showing the effects of treatment, genotype and sex on live body weight, ADG, energy and feed intake of lambs per week and over the whole experimental period is presented in Table 10. In Table 11 means of live body weight, ADG, energy and feed intake during the same periods have also been presented.

Average Daily Gain: The model explains 0.73 of the variation for ADG over the whole experimental period. During 1 - 6 weeks, 0.47 of the variation is explained by the model, and 0.88 during 7 - 12 weeks. During the same period i. e. the overall period, 1 - 6 weeks and 7 - 12 weeks, the coefficient of variation was 17.27%, 33.81% and 19.15%, respectively. Thus the first six weeks recorded higher coefficient of variation compared with the second and last. There was also a very significant (p 0.01) interaction effect of treatment x genotype during 7 - 12 weeks which is also reflected during Weeks 7 and 12. Further, this interaction can be associated with the Low-High phase of feeding whose High feeding phase proper was administered during 7 - 12 weeks.

The effect of treatment on ADG was highly significant over the whole experimental period, not significant during 1 - 6 weeks, and highly significant during 7 - 12 weeks. The effect of genotype on ADG was highly significant over the whole experimental period, very significant during 1 - 6 weeks, and significant during 7 - 12 weeks. The effect of sex on ADG was highly significant over the whole experimental period, and significant during 7 - 12 weeks. Lambs in the High-Low treatment ( 91.59 ±6.89g/d) recorded significantly less ADG over the whole experimental period compared with those in the Low-High treatment (128.10 ±7.06g/d). During 1 - 6 weeks, lambs in the High-Low treatment (114.60 ±14.37g/d) recorded higher ADG than those in the Low-High treatment (93.81 ±5.77g/d) even if the difference between them was not significant. During 7 - 12 weeks, lambs in the High-Low treatment (68.57 ±5.77g/d) recorded less ADG than those in the


[page 43↓]

Table 10: Results of ANOVA for post-weaning growth, energy and feed intake of lambs

Effects

DF

Weeks

Live body weight, kg

1

2

3

4

5

6

1 - 6

7

8

9

10

11

12

7 - 12

Total

Treatment:

1

Ns

ns

Ns

ns

Ns

ns

N/A

Ns

ns

ns

ns

ns

*

N/A

N/A

Genotype:

2

***

***

***

***

***

***

N/A

***

***

***

***

***

***

N/A

N/A

Sex:

1

Ns

ns

Ns

ns

Ns

ns

N/A

Ns

ns

ns

ns

ns

ns

N/A

N/A

Treat. X Gen.

2

Ns

ns

Ns

ns

Ns

ns

N/A

Ns

ns

ns

ns

ns

ns

N/A

N/A

R-SQ:

 

0.62

0.62

0.66

0.64

0.71

0.67

N/A

0.66

0.66

0.69

0.73

0.72

0.71

N/A

N/A

CV(%):

 

18.59

19.02

18.35

18.17

16.26

16.94

N/A

16.41

16.00

14.44

13.90

13.88

13.51

N/A

N/A

Average Daily Gain, g

Treatment:

1

      

ns

      

***

***

Genotype:

2

      

**

      

*

***

Sex:

1

      

ns

      

*

***

Treat. X Gen.

2

      

ns

      

**

ns

R-SQ:

       

0.47

      

0.88

0.73

CV(%):

       

33.81

      

19.15

17.27

Feed/Energy intake per day

Total energy intake, MJ ME/kg

Treatment:

1

Ns

ns

Ns

*

***

***

*

Ns

***

***

***

***

***

***

ns

Genotype:

2

Ns

*

*

*

**

***

**

***

***

***

***

***

***

***

***

Sex:

1

Ns

ns

Ns

ns

Ns

ns

ns

Ns

ns

ns

*

ns

**

*

ns

Treat. X Gen.

2

Ns

Ns

Ns

ns

Ns

Ns

ns

Ns

ns

ns

ns

ns

ns

ns

ns

R-SQ:

 

0.31

0.40

0.35

0.37

0.61

0.67

0.50

0.55

0.68

0.71

0.80

0.85

0.86

0.82

0.63

CV (%):

 

17.59

17.96

23.72

25.01

20.75

20.02

18.81

15.40

14.67

13.91

13.99

12.39

13.10

11.80

13.15

Energy intake above M, Factor

Treatment:

1

Ns

Ns

Ns

ns

**

**

ns

**

***

***

***

***

***

***

*

Genotype:

2

*

*

Ns

ns

Ns

Ns

ns

Ns

*

ns

ns

ns

ns

ns

ns

Sex:

1

Ns

Ns

Ns

ns

Ns

Ns

ns

Ns

ns

ns

ns

ns

*

ns

ns

Treat. X Gen.

2

Ns

ns

Ns

ns

Ns

Ns

ns

Ns

ns

ns

ns

ns

ns

ns

ns

R-SQ:

 

0.33

0.41

0.17

0.19

0.38

0.41

0.20

0.45

0.80

0.68

0.65

0.82

0.86

0.83

0.28

CV (%):

 

18.45

11.41

20.30

22.17

20.11

19.10

16.55

10.92

8.15

10.71

12.42

8.81

8.45

6.95

8.99

Total DM intake, g

Treatment:

1

Ns

ns

Ns

ns

**

**

ns

*

***

***

***

***

***

***

ns

Genotype:

2

*

**

*

*

***

***

**

***

***

***

***

***

***

***

***

Sex:

1

Ns

ns

Ns

ns

Ns

Ns

ns

Ns

*

ns

ns

ns

**

*

ns

Treat. X Gen.

2

Ns

Ns

Ns

ns

Ns

Ns

ns

Ns

ns

ns

ns

*

ns

ns

ns

R-SQ:

 

0.35

0.44

0.37

0.38

0.61

0.66

0.51

0.58

0.66

0.69

0.79

0.84

0.86

0.81

0.65

CV(%):

 

17.66

17.23

21.68

22.07

18.98

18.12

17.40

13.64

13.61

12.41

12.32

10.79

11.32

10.53

12.13

DM Conc. feed intake, g

Treatment:

1

Ns

Ns

Ns

*

***

***

**

Ns

***

***

***

***

***

***

*

Genotype:

2

Ns

*

Ns

ns

**

***

**

***

***

***

***

***

***

***

***

Sex:

1

Ns

ns

Ns

ns

Ns

Ns

ns

Ns

ns

ns

*

ns

**

*

ns

Treat. X Gen.

2

Ns

ns

Ns

ns

Ns

Ns

ns

Ns

ns

ns

ns

ns

ns

ns

ns

R-SQ:

 

0.28

0.39

0.33

0.39

0.63

0.69

0.51

0.52

0.70

0.73

0.79

0.84

0.84

0.82

0.61

CV(%):

 

17.51

18.56

25.68

27.61

22.27

21.61

19.15

16.92

15.44

15.09

15.64

14.18

15.40

12.90

13.96

DM Straw intake, g

Treatment:

1

Ns

ns

*

***

***

***

**

*

*

***

***

***

***

***

ns

Genotype:

2

**

***

***

***

***

***

***

***

***

***

**

*

ns

***

***

Sex:

1

Ns

ns

Ns

ns

Ns

Ns

ns

*

ns

ns

ns

ns

ns

ns

ns

Treat. X Gen.

2

Ns

ns

Ns

***

**

***

*

Ns

*

***

*

ns

ns

*

ns

R-SQ:

 

0.50

0.68

0.55

0.82

0.81

0.87

0.75

0.63

0.62

0.77

0.68

0.60

0.51

0.71

0.68

CV(%):

 

20.77

16.21

21.46

12.59

13.41

9.25

13.25

9.21

12.20

11.11

13.19

15.69

15.88

9.13

9.14

*** p≤0.001; ** p≤0.01;* p≤0.05; ns for not significant


[page 44↓]

Low-High treatment (162.38 ±9.81g/d) following negative gain during Week 7 and the difference between them was significant.

The C1 (123.69 ±8.80g/d) and the C2 (116.43 ±8.55g/d) recorded significantly higher ADG than the Cameroon (89.40 ±10.73g/d) over the whole experimental period. The difference between the C1 and the C2 crosses was not significant over the same period. During 1 - 6 weeks, the C1 (116.67 ±7.36g/d) and the C2 (123.10 ±8.14g/d) crosses recorded significantly higher ADG than the Cameroon (72.86 ±17.57g/d). The difference between the C1 and the C2 crosses was not significant. During 7 - 12 weeks, the C1 (130.71 ±18.78g/d) crosses recorded significantly higher ADG than both the C2 crosses (109.76 ±22.44g/d) and the Cameroon (105.95 ±11.83g/d). The difference between the C2 crosses and the Cameroon was not significant.

Thus from 7 - 12 weeks during which the High phase of the Low-High feeding level was administered, significant difference in ADG was attributable to treatment (feeding level), sex and the interaction effect of treatment and genotype unlike the case during 1 - 6 weeks when it was attributable to the effect of genotype alone. It is also noted that the C2 crosses recorded higher ADG than the C1 during the first six (1 - 6) weeks whereas the reverse was true and the difference significant during the second and last six (7 - 12).

Significantly higher ADG attained by the Low-High treatment compared with the High-Low treatment was largely (i. e. except during Week 7) associated with increased total energy intake during the High phase of feeding.

Intake of energy above maintenance: Lambs in the High-Low treatment (1.57 ±0.04) consumed less energy above of maintenance than those in the Low-High treatment (1.70 ±0.03) over the whole experimental period and the difference between the treatments was significant. During 1 - 6 weeks, lambs in the High-Low treatment (1.68 ±0.08) consumed more energy above of maintenance than those in the Low-High treatment (1.49 ±0.02) even if the difference between the treatments was not significant. The lack of any significant difference (except during Weeks 5 and 6) during this period was not expected. During 7 - 12 weeks, lambs in the High-Low treatment (1.46 ±0.01) consumed less energy above maintenance than those in the Low-High treatment (1.91 ±0.04) and the difference between the treatments was significant. Thus, the significantly higher ADG attained by the Low-High treatment compared with the High-Low one was also associated with higher energy intake above of maintenance level. Even if the effect of genotype on energy intake above maintenance was not significant over the whole experimental period and during 1 - 6 weeks and 7 - 12 weeks the Cameroon recorded the highest value over the whole experimental period followed by the C2 crosses and lastly by the C1 crosses (see Table 11).

Intake of wheat straw: Both during the first six and the second six weeks of the experiment, there was a significant (p 0.05) interaction effect of treatment and genotype. During the first six weeks of the experiment, the interaction effect of treatment and genotype was highly significant (p 0.001) between the Cameroon and the crossbred (C1 and C2) lambs. Between the C1 and C2 crosses, there was also a significant (p 0.05) effect of treatment and genotype with regard to wheat straw intake during the first six (1 - 6) weeks of the experiment. During the second six (7 - 12) weeks of the experiment, the interaction effect of treatment and genotype between the Cameroon and the C1 crossbred lambs was highly significant (p 0.001) whereas that between the Cameroon and the C2 was very significant (p 0.01) and that between the C1 and the C2 not significant. Thus significant differences in treatment x genotype interaction between the C1 and the C2 with regard to wheat straw intake could only be associated with High-Low feeding and not with Low-High feeding.


[page 45↓]

Table 11: Effects of genotype and feeding level on post-weaning growth, energy and feed intake, means ± se

Trait

N

Week

 

Week

  
  

1

2

3

4

5

6

1 – 6

7

8

9

10

11

12

7 – 12

Total

  

Live weight, kg

ADG, g

Live weight, kg

ADG, g

ADG Total g

Treatment 1
(High-Low)

15

16.9° ±1.19

17.9a ±1.27

18.7a ±1.39

19.7a ±1.39

20.3a ±1.45

21.2a ±1.46

114.6a ±14.37

20.8a ±1.37

21.4a ±1.38

22.1a ±136

22.5a ±1.38

23.5a ±1.46

24.1a ±1.33

68.6a ±5.77

91.6a ±6.89

Treatment 2
(Low-High)

15

16.6° ±1.18

17.2a ±1.25

17.5a ±1.24

18.1a ±1.27

18.9a ±1.26

19.7a ±1.33

93.8a ±5.77

21.0a ±1.40

22.0a ±1.4a

22.8a ±1.38

24.06a ±1.49

24.80a ±1.47

26.51b ±1.55

162.4b ±9.81

128.1b ±7.06

Genotype

Cameroon

10

12.3° ±0.64

12.8a ±0.66

13.0a ±0.61

13.6a ±0.75

14.0a ±0.76

14.9a ±0.79

72.9a ±17.57

15.3a ±0.83

16.1a ±0.80

16.8a ±0.79

17.2a ±0.78

17.9a ±0.81

19.3a ±0.90

106.0a ±11.83

89.4a ±10.73

C1

10

17.4b ±1.39

18.2b ±1.52

19.0b ±1.50

20.0b ±1.52

20.7b ±1.39

21.5b ±1.52

116.7b ±7.36

22.0b ±1.47

22.9b ±1.54

23.7b ±1.42

24.6b ±1.48

25.7b ±1.50

27.0b ±1.67

130.7b ±18.8

123.7b ±8.80

C2

10

20.6c ±0.53

21.7c ±0.52

22.5c ±0.70

23.1b ±0.67

24.1c ±0.67

25.0c ±0.72

123.1b ±8.14

25.4c ±0.52

26.1c ±0.48

26.8c ±0.53

28.0c ±0.49

28.8c ±0.54

29.6b ±0.55

109.8a ±22.44

116.4b ±8.55

  

Total energy intake/day, MJ ME

Treatment 1
(High-Low)

15

4.09° ±0.26

5.58a ±0.33

6.55a ±0.48

7.58a ±0.59

8.60a ±0.62

9.34a ±0.69

6.96a ±0.45

6.53a ±0.34

6.55a ±0.30

6.66a ±0.29

6.67a ±0.36

6.97a ±0.30

7.06 ±0.31a

6.74a ±0.31

6.85a ±0.36

Treatment 2
(Low-High)

14

4.48a ±0.11

5.64a ±0.27

5.80a ±0.33

6.17b ±0.29

6.29b ±0.31

6.79b ±0.38

5.86b ±0.26

7.27a ±0.38

8.70b ±0.43

8.87b ±0.44

9.40b ±0.54

10.20b ±0.60

10.85b ±0.68

9.21b ±0.47

7.54a ±0.35

Genotype

Cameroon

9

3.87a ±0.27

4.89a ±0.34

5.25a ±0.61

5.76a ±0.75

6.02a ±0.83

6.10a ±0.66

5.32a ±0.56

5.75a ±0.34

6.31a ±0.46

6.42a ±0.45

6.12a ±0.47

6.55a ±0.42

6.73a ±0.54

6.31a ±0.41

5.81a ±0.35

C1

10

4.19ab ±0.32

5.44ab ±0.44

6.21ab ±0.44

7.02ab ±0.54

7.55b ±0.45

8.72b ±0.61

6.52b ±0.36

6.83b ±0.48

7.66b ±0.56

7.85b ±0.54

8.33b ±0.60

9.00b ±0.67

9.35b ±0.80

8.17b ±0.56

7.35b ±0.37

C2

10

4.73b ±0.03

6.43b ±0.03

7.00b ±0.38

7.79b ±0.44

8.74b ±0.60

9.31b ±0.78

7.33b ±0.33

7.96c ±0.16

8.65c ±0.42

8.78c ±0.48

9.33c ±0.63

9.85b ±0.75

10.36 c ±0.86

9.16c ±0.52

8.24c ±0.18

  

Energy intake/day above Maintenance, Factor

Treatment 1
(High-Low)

15

1.11° ±0.07

1.44a ±0.07

1.63a ±0.10

1.81a ±0.13

2.00a ±0.12

2.08a ±0.10

1.68a ±0.08

1.50a ±0.02

1.47a ±0.01

1.46a ±0.01

1.44a ±0.04

1.47a ±0.02

1.45a ±0.01

1.46a ±0.01

1.57a ±0.04

Treatment 2
(Low-High)

14

1.23a ±0.05

1.48a ±0.02

1.50a ±0.04

1.56a ±0.01

1.54b ±0.01

1.62b ±0.08

1.49a ±0.02

1.66b ±0.07

1.91b ±0.06

1.89b ±0.07

1.91b ±0.06

2.02b ±0.06

2.04b ±0.06

1.91b ±0.04

1.70b ±0.03

Genotype

Cameroon

9

1.33a ±0.10

1.60a ±0.08

1.69a ±0.16

1.77a ±0.19a

1.80a ±0.21

1.76a ±0.14

1.66a ±0.14

1.66a ±0.08

1.77a ±0.12

1.74a ±0.12

1.63a ±0.12

1.69a ±0.08

1.64a ±0.10

1.69a ±0.09

1.67a ±0.07

C1

10

1.10b ±0.06

1.37b ±0.05

1.53a ±0.05

1.66a ±0.09

1.75a ±0.09

1.97a ±0.13

1.56a ±0.04

1.50a ±0.08

1.63b ±0.07

1.63a ±0.08

1.68a ±0.09

1.76a ±0.11

1.75a ±0.10

1.66a ±0.08

1.61a ±0.04

C2

10

1.09b ±0.02

1.43b ±0.02

1.51a ±0.06

1.64a ±0.07

1.77a ±0.09

1.84a ±0.13

1.55a ±0.05

1.57a ±0.03

1.67a ±0.08

1.65a ±0.08

1.70a ±0.10

1.76a ±0.13

1.80b ±0.13

1.69a ±0.09

1.62a ±0.03


[page 46↓]

Continuation: Table 11

Trait

N

Week

  

1

2

3

4

5

6

1 – 6

7

8

9

10

11

12

7 – 12

Total

  

Total DM intake/day, g

Treatment 1
(High-Low)

15

432.96a ±28.17

554.83a ±33.09

632.24a ±44.41

719.05a ±53.43

804.96a ±57.75

867.48a ±62.62

668.59a ±43.20

647.90a ±32.19

655.73a ±27.02

670.27a ±24.30

670.65a ±31.01

695.22a ±25.46

700.92a ±27.65

673.45a ±27.09

671.02a ±33.97

Treatment 2
(Low-High)

14

466.90a ±14.38

569.10a ±27.21

584.54a ±31.02

625.68a ±25.83

634.21b ±27.56

679.31b ±33.19

593.29a ±24.20

717.92b ±33.00

825.84b ±40.01

833.25b ±40.66

877.19b ±48.08

943.65b ±52.06

1000.18b ±57.77

866.34b ±41.77

729.82a ±31.61

Genotype

Cameroon

9

394.57a ±28.39

478.13a ±30.23

509.44a ±53.76

558.14a ±62.88

575.94a ±70.68

589.52a ±54.23

517.62a ±48.80

573.63a ±34.08

616.87a ±38.04

627.59a ±31.79

601.84a ±34.78

638.86a ±30.84

655.75a ±42.08

619.09a ±31.63

568.36a ±32.32

C1

10

442.96ab ±32.55

548.33a ±41.69

612.20ab ±39.65

688.63ab ±44.48

732.30b ±36.13

834.43b ±50.79

643.14b ±32.69

682.20b ±40.86

749.69b ±48.30

766.59b ±45.39

805.89b ±49.24

863.36b ±56.06

893.00b ±66.13

793.45b ±47.37

718.30b ±33.39

C2

10

505.03b ±3.13

650.34b ±2.86

696.01b ±31.82

763.57b ±36.25

844.70b ±50.45

887.24b ±63.75

724.48b ±27.38

778.47c ±14.43

834.90c ±35.38

840.54c ±39.38

886.50c ±49.79

925.61b ±57.73

968.47b ±66.45

872.42c ±41.12

798.45c ±13.90

  

Concentates, DM/day, g

Treatment 1
(High-Low)

15

281.59a ±18.44

409.52a ±25.13

494.88a ±37.64

518.25a ±47.72

668.35a ±48.11

730.49a ±55.21

527.68a ±34.77

480.41a ±26.03

476.95a ±24.04

482.87a ±24.14

484.39a ±30.00

509.93a ±24.66

518.32a ±25.48

492.15a ±25.09

509.91a ±28.56

Treatment 2
(Low-High)

14

312.16a ±5.97

403.17a ±19.49

414.47a ±24.34

437.25b ±23.32

448.77b ±23.91

487.48b ±30.55

417.22b ±19.30

532.15a ±29.95

661.58b ±31.71

682.19b ±33.41

731.05b ±41.01

797.67b ±48.38

855.25b ±53.82

709.98b ±35.51

563.60b ±25.79

Genotype

Cameroon

9

280.09a ±17.47

361.56a ±25.08

389.77a ±45.69

425.33a ±57.88

448.79a ±64.21

451.74a ±51.87

392.88a ±42.57

424.53a ±22.72

482.83a ±38.35

493.81a ±41.45

479.87a ±47.00

515.40a ±44.40

541.43a ±56.97

489.65a ±38.32

441.26a ±26.08

C1

10

288.61a ±22.94

394.11ab ±33.56

459.93ab ±35.68

522.70ab ±47.08

567.67b ±40.18

663.86b ±52.68

482.81b ±29.45

499.84b ±39.97

571.21b ±46.80

586.14b ±45.79

627.74b ±51.14

683.43b ±57.36

713.63b ±67.92

613.67b ±47.99

548.24b ±30.33

C2

10

321.93a ±2.31

463.37b ±2.71

514.31b ±31.62

579.71b ±37.26

659.23b ±50.42

711.36b ±67.08

541.65b ±27.90

594.47c ±13.11

653.76 ±35.36

667.63c ±42.18

715.54c ±55.83

762.57c ±67.35

805.30c ±76.73

699.88c ±45.96

620.77c ±15.57

  

Straw intake, DM/day, g

Treatment 1
(High-Low)

15

151.37a ±11.55

145.30a ±11.97

137.36a ±12.51

137.80a ±12.58

136.61a ±13.04

136.98a ±9.50

140.90a ±11.28

167.50a ±7.48

178.78a ±5.07

187.40a ±0.31

186.26a ±1.46

185.29a ±2.24

182.60a ±3.83

181.30a ±2.67

161.10a ±6.63

Treatment 2
(Low-High)

14

153.99a ±9.28

160.86a ±7.72

164.82b ±8.26

182.34b ±2.47

179.33b ±4.00

183.94b ±2.66

170.88b ±4.86

180.92b ±3.44

158.92b ±9.49

146.74b ±10.67

145.03b ±10.51

142.67b ±11.10

146.50b ±9.97

153.46b ±7.64

162.17a ±5.71

Genotype

Cameroon

9

116.89a ±10.62

113.30a ±10.23

114.24a ±13.07

124.65a ±18.16

117.63a ±16.58

129.48a ±15.13

119.37a ±12.04

153.52a ±10.65

145.60a ±13.35

147.98a ±16.56

148.14a ±15.97

149.67a ±15.03

151.62a ±11.85

149.42a ±10.21

134.39a ±4.65

C1

10

154.34b ±12.39

154.21b ±10.22

152.27b ±13.28

165.93b ±9.00

164.63b ±10.12

170.57b ±7.71

160.33b ±9.02

182.36b ±2.66

178.47b ±6.57

180.44b ±5.39

178.14b ±6.42

179.93b ±5.24

179.37b ±5.97

179.79b ±4.65

170.06b ±5.49

C2

10

183.10b ±3.28

186.97c ±0.38

181.70c ±3.26

183.86b ±2.13

185.47b ±1.57

175.89b ±5.13

182.83c ±1.82

184.00b ±3.21

181.14b ±2.70

172.91b ±7.41

170.96ab ±8.30

163.04ab ±12.26

163.17ab ±12.28

172.54b ±6.31

177.68b ±3.20

Different letters within columns indicate significant differences p≤0.05


[page 47↓]

The effect of treatment on the intake of wheat straw was not significant over the whole experimental period. The effect of genotype was highly significant but that of sex was not significant over the same period. During 1 - 6 weeks, the effect of treatment on the intake of wheat straw was very significant, that of genotype was highly significant whereas that of sex was not. During 7 - 12 weeks, the effect of treatment on the intake of wheat straw was highly significant, that of genotype was very significant whereas that of sex was not.

Lambs in the High-Low treatment (161.10 ±6.63g/d) consumed almost the same amount of wheat straw per lamb and per day as those in the Low-High treatment (162.17 ±5.71g/d) over the whole experimental period. During 1 - 6 weeks, lambs in the High-Low treatment (140.90 ±11.28g/d) consumed less than those in the Low-High treatment (170.88 ±4.86g/d) and the difference between the treatments was significant. During 7 - 12 weeks, lambs in the High-Low treatment (181.30 ±2.67g/d) consumed significantly more wheat straw than those in the Low-High treatment (153.46 ±7.64g/d). Thus, irrespective of treatment, the Low phase of feeding with concentrated feed was associated with increase in consumption of wheat straw. The C1 (170.06 ±5.49g/d) and C2 (177.68 ±3.20g/d) crosses consumed significantly more wheat straw than the Cameroon (134.39 ±4.65g/d) over the whole experimental period. The difference between the C1 and the C2 crosses was not significant. During 1 - 6 weeks, the C2 crosses (182.83 ±1.82g/d) consumed significantly more wheat straw than the C1 crosses (160.33 ±9.02g/d) and the Cameroon (119.37 ±12.04g/d); the difference between the C1 crosses and the Cameroon was also significant. During 7 - 12 weeks, the C1 (179.79 ±4.65g/d) and C2 (172.54 ±6.31g/d) consumed significantly more wheat straw than the Cameroon (149.42 ±10.21g/d). The difference between the C1 and the C2 crosses was not significant.

In all, the Low-High feeding treatment was associated with a significant increase in ADG compared with the High-Low treatment. Significant increase in ADG was associated with significant increase in energy intake during the High feeding phase (7 - 12 weeks). The C1 and C2 crossbred lambs achieved significantly higher ADG than the Cameroon. Between the C1 and the C2, the latter achieved higher but not significantly different ADG during the first six (1 - 6) weeks of the experiment. During the second six (7 - 12) weeks of the experiment, the C1 achieved significantly higher ADG than the C2. In either treatment, each Low feeding phase was associated with significant increase in wheat straw intake. The Cameroon and the crossbred lambs differed much with regard to their intake of wheat straw. Differences between the C1 and the C2 with regard to the same occurred during the first six (1 - 6) weeks of the experiment.

Table 12 shows the means and standard errors of end live body weight, growth and feed consumption pattern of Cameroon, C1 (Cameroon X Mutton) and C2 (Cameroon X Milk) crossbred lambs of both the High-Low and Low-High treatment groups. The Cameroon and C1 and C2 crossbred lambs in the Low-High treatment group achieved heavier end weight than those of the same genotype subjected to the High-Low treatment. This is explained by the fact that lambs in the Low-High treatment group achieved higher growth rates than those of the same genotype in the High-Low treatment group. The difference in the ADG of the C2 crosses in the Low-High treatment group was significantly higher than that of the C2 crosses in the High-Low one due to the fact that the latter suffered drastic loss of weight during the first week (7) of change-over to the Low feeding phase. Cameroon and C1 and C2 crossbred lambs in the Low-High treatment group consumed more energy above maintenance level than those of the same genotype in the High-Low treatment group although the differences between them was not significant. In both treatment groups, the trend for the Cameroon to consume the highest amount of energy above maintenance, followed by the C2 and then the C1 crossbred lambs, has been noted.


[page 48↓]

Table 12: Means and standard errors of live body weight, growth and feed intake of lambs of different genotypes in response to different feeding levels

 

Feeding level

 

High-Low

Low-High

 

Genotype, n = 5

 

Cameroon

C1

C2

Cameroon

C1

C2

Trait

Mean ± se

mean ± se

mean ± se

mean ± se

mean ± se

mean ± se

End weight, kg

18.7a
±1.26

25.0b
±2.02

28.6b
±0.68

20.0a
±1.36

29.0b
±2.52

30.6b
±0.66

ADG, g

74.5a
±18.22

105.5ab
±5.90

94.7a
±2.91

104.3ab
±8.70

141.9b
±12.14

138.1b
±9.26

MJ ME/W 0.75/d

0.73a
±0.06

0.70a
±0.01

0.70a
±0.01

0.79a
±0.02

0.75a
±0.03

0.76a
±0.02

Energy M, Factor

1.61a
±0.13

1.55a
±0.03

1.56a
±0.03

1.75a
±0.04

1.67a
±0.06

1.68a
±0.05

DM intake/d, g

555.5a
±56.93

677.1ab
±47.48

780.5b
±16.62

584.5a
±21.82

759.5b
±43.75

816.4b
±20.79

Conc. Feed/d, g

422.5a
±49.07

509.6ab
±43.47

597.7bc
±15.77

460.1a
±26.66

586.9bc
±38.78

643.8c
±24.00

Straw/d, g

133.0a
±8.33

167.5b
±7.80

182.8b
±2.34

136.1a
±3.54

172.6b
±8.46

172.5b
±5.24

Different letters within rows indicate significant differences p≤0.05


[page 49↓]

Fig. 2: Post-weaning live body weight of lambs: Reaction to different feeding levels

Except in the case of the C2 crossbred lambs, lambs in the Low-High treatment group consumed a higher amount of wheat straw than those of the same genotype in the Low-High treatment group although the differences between them were not significant (p > 0.05).

Fig.2 shows the live body weight per week of the Cameroon and of the C1 and C2 crossbred lambs subjected to the High-Low and Low-High treatments. Despite having lower live body weight (except in the case of the C2) at the beginning of the experiment, lambs in the Low-High treatment group achieved heavier end weight than those of the same genotype in the High-Low treatment group. The comparatively lower live weight of lambs of the Low-High treatment group at the beginning of the experiment may be explained by the higher (9) number of females compared to the High-Low treatment group which had 7. The proportionate break down of the number of female lambs in the High-Low and Low-High treatment groups was 2: 2 for the Cameroon, 2: 3 for the C1 and 3: 4 for the C2 crossbred lambs.

Lambs of the same genotype but belonging to different treatment groups (High-Low or Low-High) showed differences in weight reached during Week 6 i. e. before change-over. There were considerable differences in weight between the Cameroon lambs of both treatment groups. There was, however, no obvious difference in weight of the C1 crossbred lambs of both groups during week 6 but a big one in the case of the C2. The difference in weight among the C1 belonging to both treatment groups was,however, very big during Week 12. Since weight differences between groups were determined more by the Low-High feeding phase than the High-Low, the C1 are hereby identified as the most favoured genotype with regard to Low-High feeding.


[page 50↓]

Fig. 3: Average Daily Gain in response to High-Low feeding

Fig. 3 shows the ADG per week of the Cameroon lambs and of the C1 and C2 crosses subjected to the High-Low treatment. During the first six (6) weeks of the High phase of feeding, ADG from one week to the other exhibited an up- and downswing trend that did not conform to any predictable pattern of reaction of the genotypes involved. Only after the administration of the Low phase of feeding (Week 7 to Week 12) did the lambs show any predictable pattern with all lambs first being forced into the downswing to the extent that the Cameroon and C1 crosses recorded zero ADG and the C2 crosses suffered drastic loss of about -150g.

Fig. 4 shows the ADG per week of the Cameroon lambs and of the C1 and C2 crosses subjected to the Low-High treatment. It should be noted that lambs in both the High-Low and Low-High treatments were weighed on the same day using the same scale such that different responses between them can only be reasonably attributed to treatment per se. High increases in ADG occurred during Weeks 7, 10 and 12. High increases in ADG during this time should have made up much of the compensatory growth associated with the Low-High treatment. Characteristic of ADG is to assume an up-swing at one time that will be followed by a down-swing and vice versa. It appears that compensatory growth was associated more with the up-swing phase of ADG. During the High phase of the Low-High feeding treatment, the upswing tended to dominate and was clearly present during Week 7, Week 10 (except for the Cameroon lambs) and Week 12.


[page 51↓]

Fig. 4: Average Daily Gain in response to Low-High feeding

Significant increase in ADG of the Low-High treatment during 7 - 12 weeks was always accompanied by significant increase in concentrated feed intake except during Week 7. Significant increase in ADG during Week 7 cannot be associated with any significant increase in concentrated feed intake. Significant increase in concentrated feed intake of the Low-High treatment during Weeks 8 to 12, i. e. over a period of five weeks, was only matched by significant increases in ADG during Weeks 10 and 12. Thus increased feed intake was not associated with increased ADG during three weeks (8, 9 and 11) of the 6-week High phase of feeding. An ideal situation would be to match increase in feed intake with increase in ADG.

From Week 7 to Week 12, it appears that from a lower level, the Cameroon lambs required about two (2) weeks to reach their next higher level of ADG and this conforms with their relatively lower rate of growth.

Fig. 5 shows relative intake of wheat straw per week by the Cameroon lambs and the C1 and C2 crosses subjected to the High-Low feeding treatment. It shows that the Cameroon had a different pattern of consumption than that of the C1 and C2 crossbred lambs during both the High and the Low feeding phases. The Cameroon recorded lower values than both the C1 and C2 crossbred lambs during the High feeding phase but higher values during the Low feeding phase. Between the C1 and C2 crosses, the C1 clearly consumed more than the C2 during the Low feeding phase. Relative intake by the crosses and the Cameroon lambs decreased from about 38% and 28%, respectively, during Week 1 to about 17% at the end of the High feeding phase. It was up again to about 25% and 23% for the C1 and C2 crosses, respectively, during Week 12. That by the Cameroon lambs was then relatively higher at about 30%. In practice, the extent to which the crosses could utilise wheat straw might therefore depend on the degree of availability of supplementation with concentrated feed.


[page 52↓]

Fig. 5: Mean percentage wheat straw intake of lambs in the High-Low feeding treatment

In general, relative intake of wheat straw reduced with increased intake of concentrated feed and vice versa. Relative intake of wheat straw by the crosses was more stable than that of the Cameroon lambs during the Low feeding phase. During the High feeding phase, there was increased substitution of wheat straw by concentrated feed.

5.3.2 Reaction to high ambient temperature during the day and of alternating feeding levels

The results show the productive performance and physiological reaction of C2 (Cameroon X Mutton) compared with that of the pure Cameroon lambs when subjected to high (31°C/50%RH) ambient temperature during the day and low (15°C/70%RH) at night combined with alternating feeding levels (High-Low-High) administered in the form of ad libitum feeding during the first 4 weeks followed by restriction (1.5 times above maintenance) during the next 4 weeks and lastly ad libitum feeding during the last 4 weeks. Feeding with wheat straw was fixed at a maximum of 200g per lamb per day.

5.3.2.1 Post-weaning growth performance

The analysis of variance showing the effects of genotype and sex on live body weight, ADG, energy and feed intake of lambs per week, during 1 - 4 weeks, 5 - 8 weeks, 9 - 12 weeks and over the whole experimental period is presented in Table 13. In Table 14 means of live body weight, ADG, energy and feed intake during the same periods have also been presented.

Average Daily Gain: The model explains 0.64 of the variation for ADG over the whole experimental period. During the first four and the second four weeks, the model explains only a small amount of the variation. During 9 - 12 weeks in which realimentation took place, the model explains 0.69 of the variation. During the same period i. e. the overall period, 1 - 4 weeks, 5 - 8 and 9 - 12 weeks, the coefficient of variation was 17.31%, 38.13%, 47.76% and 31.98%, respectively.

The effect of genotype on ADG was not significant over the whole experimental period whereas that of sex was. During 1 - 4 weeks and 5 - 8 weeks, the effect of genotype and sex on ADG was not significant. During 9 - 12 weeks, the effect of genotype and sex on ADG was significant. Over the whole experimental period, the C2 (120.24 ±11.08g/d) achieved higher ADG than the pure Cameroon (98.57 ±12.93g/d) even if the difference between them was not significant. Following the Low feeding phase (5 - 8 weeks), the C2 crossbred lambs (167.86 ±26.75g/d) achieved significantly higher ADG [page 53↓]than the Cameroon (100.71 ±28.38g/d) during the second High feeding phase i. e. during 9 - 12 weeks. Males gained significantly more than females over the whole experimental period and during the second High feeding phase from 9 - 12 weeks.

Intake of energy above maintenance: The model explains 0.50 of the variation for energy intake above maintenance requirement over the whole experimental period. During 1 - 4 weeks, the model explains 0.73 of the variation, 0.32 during 5 - 8 weeks, and 0.45 during 9 - 12 weeks. During the same period i. e. the overall period, 1 - 4 weeks, 5 - 8 and 9 - 12 weeks, the coefficient of variation was 5.90%, 10.29%, 1.40% and 8.47%, respectively.

The effect of intake of energy above maintenance requirement was significantly affected by genotype over the whole experimental period. The effect of sex on intake of energy above maintenance requirement over the same period was not significant. During the first High feeding phase (1 - 4 weeks) the effect of genotype on intake of energy above maintenance requirement was very significant but that of sex was not. During the Low feeding phase (5 - 8 The Cameroon (1.63 ±0.03) lambs consumed significantly more energy above maintenance requirement than the C2 crosses (1.48 ±0.05). During the first High feeding phase (1 - 4 weeks), the Cameroon (1.74 ±0.06) still consumed significantly more energy above maintenance requirement than the C2 crosses (1.31 ±0.08). During the Low feeding phase (5 - 8 weeks), the Cameroon consumed 1.49 ±0.13 times more energy above maintenance requirement compared with 1.58 ±0.10 for the C2 crosses and as expected and the difference between the genotypes was not significant. During the second High feeding phase (9 - 12 weeks), the Cameroon (1.69 ±0.06) and the C2 crosses (1.69 ±0.10) consumed a similar amount of energy above maintenance level. During 9 - 12 weeks, males (1.77 ±0.03) recorded a significantly higher value than females (1.56 ±0.10).

Significantly higher ADG achieved by the C2 crossbred lambs during 9 - 12 weeks, compared with the Cameroon, was not due to any difference in intake of energy above maintenance. The C2 crossbred lambs therefore responded better to the Low-High feeding element than did the Cameroon even under conditions of high ambient temperature during the day.

weeks), the effect of genotype and sex on intake of energy above maintenance requirement was not significant. During the second and last High feeding phase (9 - 12 weeks), the effect of genotype on intake of energy above maintenance requirement was not significant but that of sex was.


[page 54↓]

Table 13: Results of ANOVA of post-weaning live weight, ADG and energy and feed intake of lambs per week

Trait

Week

               
 

1

2

3

4

1 - 4

5

6

7

8

5 - 8

9

10

11

12

9 - 12

Total

Live weight

Genotype

***

***

***

***

N/A

***

***

***

***

N/A

***

***

***

***

N/A

N/A

Sex

*

*

**

**

N/A

**

**

**

**

N/A

**

**

**

**

N/A

N/A

R-SQ

0.87

0.86

0.91

0.89

N/A

0.88

0.90

0.90

0.91

N/A

0.88

0.90

0.90

0.89

N/A

N/A

CV (%)

11.30

11.08

7.97

9.06

N/A

8.71

8.31

8.35

7.50

N/A

8.57

8.71

8.87

9.40

N/A

N/A

Average Daily Gain

Genotype

Ns

Ns

Ns

Ns

ns

ns

Ns

ns

ns

Ns

ns

ns

ns

ns

*

ns

Sex

Ns

Ns

Ns

Ns

ns

ns

Ns

ns

ns

Ns

ns

ns

ns

ns

*

*

R-SQ

0.00

0.01

0.05

0.13

0.00

0.08

0.12

0.33

0.05

0.13

0.04

0.47

0.34

0.27

0.69

0.64

CV (%)

73.48

121.70

116.86

79.31

38.13

234.30

105.99

54.82

367.15

47.76

58.95

100.74

130.99

70.39

31.98

17.31

Total energy intake, ME MJ

Genotype

Ns

Ns

Ns

Ns

ns

***

***

***

***

***

**

**

**

ns

**

**

Sex

Ns

ns

Ns

Ns

ns

**

**

**

***

**

**

**

**

ns

**

**

R-SQ

0.03

0.14

0.31

0.46

0.22

0.91

0.90

0.87

0.92

0.90

0.84

0.90

0.86

0.53

0.83

0.81

CV (%)

15.44

21.10

11.61

12.71

13.11

6.54

5.73

6.97

5.03

5.78

7.89

7.73

12.30

25.80

10.88

8.20

Energy intake above M, Factor

Genotype

**

*

**

**

**

ns

Ns

ns

ns

Ns

ns

ns

ns

ns

ns

*

Sex

*

ns

Ns

Ns

ns

ns

Ns

ns

ns

Ns

ns

*

ns

ns

*

ns

R-SQ

0.76

0.48

0.70

0.69

0.73

0.07

0.07

0.23

0.37

0.32

0.11

0.50

0.54

0.28

0.45

0.50

CV (%)

14.48

15.26

11.79

8.84

10.29

2.39

2.67

3.36

2.01

1.40

6.67

6.51

11.33

23.03

8.47

5.90

Total DM intake

Genotype

Ns

Ns

Ns

Ns

ns

***

***

***

***

***

**

**

**

ns

**

**

Sex

Ns

Ns

ns

Ns

ns

**

**

**

***

**

**

**

**

*

**

**

R-SQ:

0.02

0.24

0.41

0.49

0.33

0.91

0.92

0.87

0.92

0.91

0.86

0.88

0.85

0.50

0.81

0.81

CV (%)

13.43

18.27

9.28

11.26

11.32

5.01

5.26

6.41

4.65

5.07

6.72

7.83

11.64

24.21

10.77

7.65

Concentrates, DM

Genotype

Ns

Ns

ns

Ns

ns

***

***

***

***

***

**

**

**

ns

**

*

Sex

Ns

Ns

ns

Ns

ns

**

**

*

**

**

*

***

**

*

**

**

R-SQ

0.11

0.07

0.26

0.43

0.16

0.88

0.89

0.85

0.90

0.89

0.81

0.90

0.86

0.55

0.84

0.79

CV (%)

17.93

24.11

14.29

14.38

15.15

7.28

6.48

7.94

6.14

6.82

9.16

8.14

13.25

27.31

11.19

8.95

Straw intake, DM

Genotype

*

*

ns

Ns

*

ns

*

ns

ns

Ns

ns

ns

ns

ns

ns

ns

Sex

*

*

ns

Ns

ns

ns

*

ns

ns

Ns

*

ns

ns

ns

ns

ns

R-SQ

0.68

0.70

0.45

0.39

0.62

0.57

0.71

0.43

0.31

0.52

0.62

0.25

0.20

0.06

0.22

0.53

CV (%)

11.08

14.71

17.68

17.09

12.88

6.47

8.83

11.48

13.18

9.21

9.60

20.69

21.21

16.20

16.36

10.81

*** p ≤ 0.001; ** p ≤ 0.01;* p ≤ 0.05; ns for not significant


[page 55↓]

Table 14: Means and standard errors of post-weaning live weight, ADG and energy and feed intake of lambs per week by genotype and sex

   

Week

Trait

n

Start

1

2

3

4

1 - 4

5

6

7

8

5 - 8

9

10

11

12

9 - 12

Total

Live weight, kg

Genotype

                  

Cameroon

5

12.1a
±1.43

13.1a
±1.55

13.7a
±1.68

14.8a
±1.35

15.5a
±1.57

N/A

15.9a ±
1.49

16.4a ±1.49

17.1a ±
1.72

17.5a ±
1.47

N/A

18.7a ±
1.77

19.0a ±
1.71

19.3a ±
2.01

20.3a ±
2.15

N/A

N/A

C2

5

19.0b
±1.10

20.0b
±0.82

20.8b
±0.62

21.5b
±0.87

22.5b
±0.74

N/A

22.6b
±0.84

23.2b
±0.99

24.3b
±0.87

24.4b
±1.17

N/A

25.8b
±1.01

27.4b
±1.52

28.0b
±1.52

29.1b
±1.82

N/A

N/a

Sex

                  

Male

6

 

18.1a
±1.54

18.9a
±1.43

19.8a
±1.47

20.6a
±1.43

N/A

20.9a
±1.45

21.5a
±1.50

22.6a
±1.50

22.8a
±1.61

N/A

24.2a
±1.59

25.4a
±2.00

26.2a
±1.97

27.6a
±2.10

N/A

N/A

Female

4

 

14.2b
±2.46

14.8b
±2.71

15.8b
±2.25

16.5b
±2.62

N/A

16.8b
±2.38

17.2
±2.37

17.9b
±2.67

18.2b
±2.21

N/A

19.3b
±2.50

19.8b
±2.67

19.9b
±2.94

20.5b
±2.86

N/A

N/A

Average Daily Gain, g

Genotype

                  

Cameroon

5

 

142.9a
±22.59

97.1a
±36.53

160.0a
±49.16

85.7a
±46.73

121.4a
±14.98

65.7a
±41.06

65.7a
±21.00

100.0a
±34.11

62.9a
±50.63

73.6a
±5.71

168.6a
±55.59

40.0a
±40.76

48.6a
±47.94

145.7a
±48.95

100.7a
±28.38

98.6a
±12.93

C2

5

 

137.1a
±56.53

114.3a
±66.85

105.7a
±77.80

137.1a
±24.99

123.6a
±23.24

17.1a
±40.25

82.9a
±44.58

165.7a
±32.45

11.4a
±62.83

69.3a
±20.84

194.3a
±31.82

231.4a
±78.17

88.6a
±42.23

157.1a
±54.96

167.9b
±26.75

120.2a
±11.08

Sex

                  

Male

6

 

138.1a
±45.28

109.5a
±49.85

126.2a
±38.23

121.4a
±26.28

123.8a
±20.34

38.1a
±37.19

92.9a
±18.72

154.8a
±27.95

35.7a
±43.29

80.4a
±12.50

192.9a
±44.53

176.2a
±84.33

109.5a
±29.89

195.2a
±40.35

168.4a
±21.56

124.2a
±9.64

Female

4

 

142.9a
±32.47

100.0a
±59.19

142.9a
±104.98

96.4a
±58.1

120.5a
±15.46

46.4a
±50.30

46.4a
±52.93

100.0a
±45.18

39.3a
±81.94

50.0a
±17.09

164.3a
±43.06

75.0a
±27.59

7.1a
±52.97

85.7a
±50.84

83.0b
±29.21

87.2b
±8.66

Total energy intake/day, ME MJ

Genotype

                  

Cameroon

5

 

4.59a
±0.13

5.41a
±0.51

6.33a
±0.47

6.52a
±0.57

5.71a
±0.41

5.27a
±0.36

5.35a
±0.34

5.48a
±0.37

5.76a
±0.37

5.46a
±0.36

6.78a
±0.58

7.31a
±0.74

6.75a
±0.89

7.31a
±0.76

7.04a
±0.72

6.07a
±0.49

C2

5

 

4.42a
±0.39

5.83a
±0.53

6.16a
±0.21

6.91a
±0.36

5.83a
±0.30

6.80b
±0.18

6.93b
±0.20

7.08b
±0.21

7.22b
±0.23

7.01b
±0.21

8.49b
±0.25

9.50b
±0.52

9.99b
±0.73

8.66a
±1.53

9.16b
±0.72

7.33b
±0.33

Sex

                  

Male

6

 

4.48a
±0.32

5.89a
±0.44

6.57a
±0.29

7.23a
±0.23

5.71a
±0.41

6.42a
±0.31

6.53a
±0.34

6.67a
±0.37

6.95a
±0.31

5.46a
±0.36

8.24a
±0.31

9.36a
±0.46

9.50a
±0.67

9.37a
±0.56

7.04a
±0.72

7.27a
±0.25

Female

4

 

5.54a
±0.16

5.22a
±0.60

5.76a
±0.32

5.95a
±0.57

5.37a
±0.39

5.45b
±0.57

5.56b
±0.56

5.68b
±0.55

5.81b
±0.51

5.62b
±0.55

6.73b
±0.76

6.98b
±0.84

6.67b
±1.30

5.91b
±1.44

6.57b
±0.90

5.85b
±0.59

Energy intake/day above Maintenance, Factor

Genotype

                  

Cameroon

5

 

1.53a
±0.10

1.70a
±0.06

1.87a
±0.09

1.86a
±0.05

1.74a
±0.06

1.47a
±0.02

1.47a
±0.02

1.46a
±0.03

1.50a
±0.01

1.47a
±0.01

1.68a
±0.07

1.78a
±0.07

1.61a
±0.11

1.69 ±
0.04a

1.69 ±
0.06a

1.63 ±
0.03a

C2

5

 

1.05b
±0.11

1.34b
±0.12

1.38b
±0.07

1.49b
±0.07

1.31b
±0.08

1.46a
±0.01

1.46a
±0.02

1.44a
±0.02

1.46a
±0.01

1.45a
±0.01

1.65a
±0.01

1.76a
±0.06

1.82a
±0.10

1.51 ±0.24a

1.69 ±0.10a

1.48 ±0.05b

Sex

                  

Male

6

 

1.18a
±0.13

1.48a
±0.15

1.60a
±0.15

1.69a
±0.11

1.49a
±0.13

1.47a
±0.01

1.46a
±0.01

1.43a
±0.01

1.48a
±0.02

1.46a
±0.00

1.69a
±0.03

1.85a
±0.04

1.83a
±0.07

1.73a
±0.03

1.77a
±0.03

1.57a
±0.05

Female

4

 

1.46a
±0.15

1.57a
±0.07

1.65a
±0.12

1.65a
±0.11

1.58a
±0.10

1.46a
±0.02

1.47a
±0.02

1.47a
±0.03

1.48a
±0.02

1.47a
±0.02

1.63a
±0.07

1.65b
±0.06

1.55a
±0.14

1.40a
±0.29

1.56b
±0.10

1.54a
±0.06

Different letters within columns indicate significant differences p≤0.05


[page 56↓]

Continuation: Table 14

Trait

 

Week

 

n

(start)

1

2

3

4

1 - 4

5

6

7

8

5 - 8

9

10

11

12

9 - 12

Total

Total DM intake/day, g

Genotype

                  

Cameroon

5

 

471.4a
±18.10

528.4a
±49.45

609.9a
±40.27

622.2a
±46.71

558.0a
±37.62

536.0a
±31.57

535.3a
±32.26

552.3a
±33.61

582.2a
±32.22

551.5a
±31.93

663.0a
±51.64

694.6a
±62.23

647.5a
±71.41

705.6a
±62.40

677.7a
±60.02

595.7a
±42.69

C2

5

 

471.9a
±33.18

588.5a
±43.71

615.3a
±17.34

673.6a
±34.19

587.3a
±25.71

674.0b
±17.96

684.9b
±20.84

696.9b
±23.57

706.2b
±27.12

690.5b
±22.24

814.1b
±27.72

895.4b
±50.66

935.8b
±69.56

825.0a
±136.24

867.6b
±68.83

715.1b
±33.23

Sex

                  

Male

6

 

477.4a
±27.35

589.4a
±36.01

645.1a
±18.09

692.4a
±17.60

601.1a
±19.81

641.4
±28.26

648.7a
±31.77

663.4a
±34.83

688.3a
±28.46

660.4a
±30.57

797.2
±29.17

877.4
±45.15

888.0a
±62.26

883.2a
±51.74

861.4a
±45.56

707.6a
±24.45

Female

4

 

463.1a
±21.70

512.1a
±59.88

563.9a
±32.73

581.1a
±53.70

530.0a
±40.62

550.2b
±50.07

552.3b
±52.32

566.6b
±47.51

578.0b
±41.25

561.8b
±47.63

650.7b
±63.76

671.5b
±74.57

647.1b
±112.15

588.3b
±127.69

639.4b
±79.77

577.1b
±54.27

Concentrates, DM/day, g

Genotype

                  

Cameroon

5

 

326.6a
±6.86

404.6a
±39.15

478.7a
±40.13

497.5a
±49.48

426.8a
±32.24

377.5a
±29.30

389.9a
±26.57

396.2a
±30.24

416.6a
±30.61

395.1a
±28.96

505.9a
±47.68

560.6a
±63.58

513.1a
±78.06

552.3a
±65.48

533.0a
±61.97

451.6a
±40.42

C2

5

 

300.2a
±33.20

421.7a
±46.44

450.5a
±18.98

517.5a
±27.57

422.5a
±26.02

500.8b
±14.09

512.1b
±14.32

524.8b
±14.65

538.4b
±15.48

519.0b
±14.49

645.8b
±16.32

732.8b
±39.77

775.5b
±56.63

662.3a
±23.87

704.1b
±55.59

548.5b
±23.43

Sex

                  

Male

6

 

305.8a
±27.67

430.1a
±39.20

488.5a
±29.33

549.9a
±22.61

443.6
±25.85

469.7a
±24.99

479.6a
±25.92

490.2a
±29.18

511.7a
±25.00

487.8a
±26.13

621.6a
±24.61

725.5a
±34.69

739.2a
±52.08

722.8a
±44.24

702.2a
±37.03

544.5a
±19.23

Female

4

 

324.9a
±8.57

387.7a
±44.79

428.8a
±24.19

444.0a
±43.74

396.3a
±27.35

393.4b
±46.92

408.1b
±43.90

416.0b
±45.81

426.2b
±45.02

410.9b
±45.40

507.3b
±64.71

528.5b
±69.18

502.0b
±108.68

434.1b
±116.95

493.0b
±73.94

433.4b
±46.92

Straw intake, DM/day, g

Genotype

                  

Cameroon

5

 

144.9a
±13.42

123.8a
±12.35

131.3a
±13.63

124.7a
±9.74

131.2a
±9.86

158.4a
±3.19

145.4a
±7.31

156.2a
±4.78

165.5a
±3.67

156.4a
±3.59

157.1a
±5.72

134.0a
±10.05

134.3a
±7.90

153.3a
±7.88

144.7a
±6.09

144.1a
±2.90

C2 (Camer. X Mutton)

5

 

171.7b
±7.82

166.8b
±12.35

164.7a
±10.45

156.1a
±10.50

164.8b
±9.90

173.1a
±7.53

172.9b
±9.50

172.1a
±12.75

167.8a
±15.15

171.5a
±11.14

168.3a
±13.01

162.6a
±15.42

160.3a
±16.76

162.7a
±13.11

163.5a
±14.32

166.6a
±11.65

Sex

                  

Male

6

 

171.6a
±4.96

159.2a
±11.69

156.6a
±12.88

142.6a
±12.74

157.5a
±9.81

171.7a
±4.58

169.1a
±6.87

173.2a
±6.53

176.6a
±4.29

172.7a
±5.09

175.6a
±4.83

151.9a
±12.57

148.8a
±12.19

160.5a
±8.57

159.2a
±9.37

163.1a
±7.19

Female

4

 

138.2b
±16.36

124.4b
±17.60

135.1a
±14.75

137.1a
±11.63

133.7a
±14.41

156.9a
±7.73

144.2b
±12.41

150.6a
±12.39

151.8a
±15.38

150.8a
±10.76

143.4b
±10.50

143.0a
±18.02

145.0a
±18.37

154.2a
±14.73

146.4a
±14.99

143.7a
±11.87

Different letters within columns indicate significant differences p≤0.05


[page 57↓]

Fig. 6: Mean daily concentrated feed intake of lambs subjected to high ambient temperature and alternating feeding levels

Intake of wheat straw: The Cameroon consumed 144.08 ±2.90g/d of wheat straw over the whole experimental period compared with 166.60 ±11.65g/d for the C2 crosses. The difference between the Cameroon and the C2 crosses was not significant. During the first High feeding phase from 1 - 4 weeks, the C2 crosses (164.82 ±9.90g/d), however, consumed significantly more wheat straw than the Cameroon (131.15 ±9.86g/d). The failure of the C2 crossbred lambs to consume all the concentrated feed provided to them during the first four (1 - 4) weeks was compensated for through increased wheat straw intake.

In all, the C2 achieved higher but not significantly different ADG than the Cameroon over the whole experimental period. However, the C2 achieved higher and significantly different ADG than the Cameroon during realimentation in the second High feeding phase (9 - 12 weeks) despite the fact that energy intake above maintenance level was not significantly different between both genotypes.

Fig. 6 shows intake of concentrated feed per day and per week by Cameroon and C2 (Cameroon X Mutton) crossbred lambs during the first High feeding phase, during the Low and the second High feeding phases. The Cameroon and the C2 crosses consumed almost similar amounts of concentrated feed during the first four weeks after which the C2 always consumed more during the Low phase and the second High phase of feeding. The difference between the Cameroon and the C2 crosses was significant during the period, 5 - 11 weeks. Thus at least after the fourth week, the concentrated feed intake of the C2 was no longer disadvantaged compared with that of the Cameroon.

Fig. 7 shows intake of energy above maintenance level per day and per week by Cameroon and C2 (Cameroon X Mutton) crossbred lambs during the first High feeding phase, during the Low and the second High feeding phases. The level of consumption above maintenance was lower in the C2 crosses than in the Cameroon during the first four weeks. This could be associated with the fact that during the first three weeks, the C2 crosses rejected more concentrated feed (3583g) than the Cameroon (2328g). It is also noted that during the same period, the amount of wheat straw rejected by the Cameroon was 2.7 times more than that rejected by the C2 crosses. Level of consumption above maintenance during the second High feeding phase (9 - 12 weeks) was higher for C2 crosses than for the Cameroon during Week 11.


[page 58↓]

Fig. 7: Intake of energy above maintenance level by lambs subjected to high ambient temperature and alternating feeding levels

Fig. 8: Mean daily wheat straw intake of lambs subjected to high ambient temperature and alternating feeding levels

Fig. 8 shows absolute intake of wheat straw per day and per week by Cameroon and C2 (Cameroon X Mutton) crossbred lambs during the first High feeding phase, during the Low and the second High feeding phases. Except during Week 4, absolute intake of wheat straw by the C2 crosses was more stable than that by the Cameroon. Intake of the same by the Cameroon though varying much from week to week, tended to be highest during the Low phase of feeding.


[page 59↓]

Fig. 9: Mean percentage wheat straw intake of lambs in response at high temperature and alternating feeding levels

Fig. 9 shows relative intake of wheat straw per day and per week by Cameroon and C2 (Cameroon X Mutton) crossbred lambs during the first High feeding phase, during the Low and the second High feeding phases. The Cameroon had a different pattern of consumption than the C2 crossbred lambs during the first High feeding phase and during both the Low and the second High feeding phases. Relative consumption by the Cameroon was lower during the first High feeding phase but higher than that of the C2 (except during Week 12) during both the Low and the second High feeding phases.

Relative intake of wheat straw by both the Cameroon and the C2 crosses reduced during the first High phase of feeding (1 - 4 weeks), then increased slightly during the Low feeding phase (5 - 8 weeks) and was more stable during the second High feeding phase (9 - 12 weeks).

5.3.2.2 Physiological reaction to high ambient temperature

The analysis of variance showing the effects of genotype and sex on rectal temperature and breathing rate of Cameroon lambs and C2 (Cameroon X Mutton) crosses is presented in Table 15. Both rectal temperature and breathing rate were measured at 1200 hrs after six (6) hours of exposure to high ambient temperature (31°C/50%RH) and at 2000 hrs after two (2) hours change-over to low ambient temperature (15°C/70%RH). It shows the reaction of the lambs over the whole experimental period and during the first High feeding phase (1 - 4 weeks), the Low feeding phase (5 - 8 weeks) and the second High feeding phase (9 - 12 weeks). In Table 16 means of rectal temperature and breathing rate the same periods have also been presented.

Rectal temperature: The model explains 0.78 of the variation for rectal temperature during the day at 1200 hrs and at high ambient temperature of 31°C/50%RH over the whole experimental period. During the period of conditioning, 1 - 4 weeks, 5 - 8 weeks and 9 - 12 weeks, the model explains 0.61, 0.33, 0.81, and 0.57 of the variation for this trait. During the same period i. e. the overall period, period of conditioning, 1 - 4 weeks, 5 - 8 and 9 - 12 weeks, the coefficient of variation was 0.22%, 0.28%, 0.37%, 0.30% and 0.35%, respectively.

The effect of genotype on rectal temperature measured at 1200 hrs was significant over the whole experimental period but not significant during the period of conditioning and during the first High feeding phase (1 - 4 weeks). The effect of genotype on the same was very significant during the Low feeding phase (5 - 8 weeks) and significant during the second High feeding phase (9 - 12 weeks). The effect of sex on rectal temperature measured at 1200 hrs was very significant over the whole period of the experiment. The effect of sex was also significant during the [page 60↓]period of conditioning, not significant during 1 - 4 weeks, very significant during 5 - 8 weeks and not significant during 9 - 12 weeks.

The Cameroon (39.22 ±0.07°C) recorded lower rectal temperature at 1200 hrs over the whole experimental period than the C2 crosses (39.38 ±0.05°C) which recorded higher. The difference between the Cameroon and the C2 crosses was significant. The significant difference in rectal temperature between the Cameroon and the C2 crosses at 1200 hrs over the whole experimental period is explained by significant differences occurring during 5 - 8 weeks and during 9 - 12 weeks (see Table 16). Males (39.21 ±0.04°C) recorded lower rectal temperature at 1200 hrs over the whole experimental period than females (39.43 ±0.08°C). Females always recorded higher rectal temperature at 1200 hrs than males and the difference between them was significant during the period of conditioning, during 5 - 8 weeks and during 9 - 12 weeks (see table 16).

The significant effect of genotype on rectal temperature at 1200 hrs and at high ambient temperature of 31°C/50%RH was thus associated with the Low feeding phase during 5 - 8 weeks and with the second High feeding phase during 9 - 12 weeks. The significant effect of sex on the same trait was associated with the period of conditioning and with the Low feeding phase during 5 - 8 weeks.

The model explains 0.68 of the variation for rectal temperature at 2000 hrs at low ambient temperature of 15°C/70%RH over the whole experimental period. During the period of conditioning, 1 - 4 weeks, 5 - 8 weeks and 9 - 12 weeks, the model explains 0.32, 0.28, 0.79, and 0.52 of the variation for this trait. During the same period i. e. the overall period, period of conditioning, 1 - 4 weeks, 5 - 8 and 9 - 12 weeks, the coefficient of variation was 0.21%, 0.43%, 0.26%, 0.24% and 0.28%, respectively.

The effect of genotype on rectal temperature measured at 2000 hrs was not significant over the whole experimental period, during the period of conditioning and during the 1 - 4 weeks. The effect of the same was significant during the Low feeding phase (5 - 8 weeks) but not significant during the second High feeding phase (9 - 12 weeks). The effect of sex on rectal temperature measured at 2000 hrs was significant over the whole experimental period but not significant during the period of conditioning and during 1 - 4 weeks. During the Low feeding phase (5 - 8 weeks), the effect of sex on the same trait was very significant but not significant during the High feeding phase (9 - 12 weeks). Rectal temperature measured at 2000 hrs amounted to 39.520 ±0.06°C for the Cameroon over the whole experimental period and to 39.41 ±0.04°C for the C2 crosses and the difference between them was not significant. The Cameroon always recorded higher rectal temperature at 2000 hrs than the C2 crosses but a significant difference between them was only recorded during the Low phase (5 - 8 weeks). Males (39.40 ±0.04°C) recorded lower rectal temperature over the whole experimental period than the females (39.56 ±0.06°C) and the difference between them was significant. Females always recorded higher rectal temperature at 2000 hrs than males but significant difference between them were only recorded during the whole experimental period already referred to and during the Low feeding phase (5 -8 weeks).


[page 61↓]

Table 15: Results of ANOVA for rectal temperature and breathing rate per minute during the high, low and high feeding phases and over the whole experimental period

 

Control (start)

High feed (1-4 weeks)

Low feed (5-8 weeks)

High feed (9-12 weeks)

Total
(1-12 weeks)

 

Rectal temperature

1. Day (1200 hrs)

     

Genotype

Ns

Ns

**

*

*

Sex

*

Ns

**

ns

**

R-SQ

0.61

0.33

0.81

0.57

0.78

CV (%)

0.28

0.37

0.30

0.35

0.22

2. Night (2000 hrs)

     

Genotype

Ns

Ns

*

ns

ns

Sex

Ns

Ns

**

ns

*

R-SQ

0.32

0.28

0.79

0.52

0.68

CV (%)

0.43

0.26

0.24

0.28

0.21

 

Breathing rate

1. Day (1200 hrs)

     

Genotype

*

Ns

*

*

*

Sex

Ns

Ns

*

*

*

R-SQ

0.56

0.15

0.73

0.72

0.66

CV (%)

17.63

12.72

9.56

12.64

9.25

2. Night (2000 hrs)

     

Genotype

Ns

Ns

ns

ns

ns

Sex

Ns

Ns

ns

ns

ns

R-SQ

0.41

0.38

0.32

0.25

0.27

CV (%)

18.95

20.37

17.94

23.60

19.96

*** p≤0.001; ** p≤0.01;* p≤0.05; ns for not significant; DF Degrees of freedom = 1

The significant effect of genotype and sex on rectal temperature at 2000 hrs at low ambient temperature of 15°C/70%RH was thus associated with the Low feeding phase during 5 - 8 weeks.

Breathing rate: The model explains 0.66 of the variation for breathing rate during the day at 1200 hrs at high ambient temperature of 31°C/50%RH over the whole experimental period. During the period of conditioning, 1 - 4 weeks, 5 - 8 weeks and 9 - 12 weeks, the model explains 0.56, 0.15, 0.73, and 0.72 of the variation for this trait. During the same period i. e. the overall period, period of conditioning, 1 - 4 weeks, 5 - 8 and 9 - 12 weeks, the coefficient of variation was 9.25%, 17.63%, 12.72%, 9.56% and 12.64%, respectively.


[page 62↓]

Table 16: Rectal temperature and breathing rate per minute of lambs during the different feeding level phases at high and low ambient temperature, means ± se

 

N

Control (start)

High feed
(1-4 weeks)

Low feed
(5-8 weeks)

High feed
(9-12 weeks)

Total
(1-12 weeks)

 

Rectal temperature

1. Day (1200 hrs)

      

Genotype

      

Cameroon

5

39.25a ±0.08

39.39a ±0.09

39.13a ±0.07

39.12a ±0.08

39.22a ±0.07

C2

5

39.37a ±0.05

39.43a ±0.05

39.39b ±0.10

39.33b ±0.07

39.38b ±0.05

Sex

      

Male

6

39.23a ±0.05

39.34a ±0.05

39.14a ±0.05

39.15a ±0.07

39.21a ±0.04

Female

4

39.43b ±0.06

39.51a ±0.09

39.44b ±0.13

39.32a ±0.09

39.43b ±0.08

2. Night (2000 hrs)

      

Genotype

      

Cameroon

5

39.30a ±0.08

39.64a ±0.05

39.48a ±0.07

39.51a ±0.07

39.52a ±0.06

C2

5

39.15a ±0.07

39.57a ±0.04

39.33b ±0.08

39.38a ±0.04

39.41a ±0.04

Sex

      

Male

6

39.18a ±0.07

39.57a ±0.03

39.30a ±0.06

39.38a ±0.05

39.40a ±0.04

Female

4

39.29a ±0.10

39.66a ±0.07

39.57b ±0.05

39.53a ±0.06

39.56b ±0.06

 

Breathing rate

1. Day (1200 hrs)

      

Genotype

      

Cameroon

5

39.65a ±3.77

77.74a ±2.73

66.17a ±3.85

66.25a ±6.84

67.71a ±3.73

C2

5

55.55b ±3.23

75.86a ±5.60

79.51b ±4.95

83.67b ±5.32

77.82b ±4.44

Sex

      

Male

6

47.50a ±5.50

74.10a ±4.30

67.38a ±3.24

67.33a ±6.10

67.90a ±3.64

Female

4

47.75a ±4.25

80.84a ±3.19

81.03b ±6.25

86.41b ±4.75

80.07b ±3.83

2. Night (2000 hrs)

      

Genotype

      

Cameroon

5

16.15a ±1.56

18.13a ±1.45

17.44a ±1.58

22.86a ±2.92

19.31a ±1.95

C2

5

13.35a ±1.09

14.84a ±1.72

16.82a ±1.51

24.95a ±2.42

18.75a ±1.75

Sex

      

Male

6

13.67a ±1.46

15.28a ±1.38

15.73a ±1.19

21.83a ±2.45

17.48a ±1.53

Female

4

16.38a ±0.94

18.31a ±2.02

19.23a ±1.42

27.02a ±2.11

21.36a ±1.63

Different letters within columns indicate significant differences p≤0.05


[page 63↓]

The effect of genotype on breathing rate measured at 1200 hrs was significant over the whole experimental period and during the period of conditioning. The effect of genotype on the same was not significant during the first High feeding phase (1 - 4 weeks) but was significant during the subsequent Low (5 - 8 weeks) and High (9 - 12 weeks) phases. The effect of sex on breathing rate measured at 1200 hrs was significant over the whole experimental period. The effect of the same was not significant during the period of conditioning and during the first High phase (1 - 4 weeks). The same was again significant during the subsequent Low (5 - 8 weeks) and High (9 - 12 weeks) phases.

Fig. 10: Effect of fluctuating temperatures (high and low during the day and at night, respectively) on rectal temperature of Cameroon and Cameroon x Mutton lambs during the post-weaning growth phase

The Cameroon (67.71 ±3.73) recorded significantly lower average breathing rate per minute than the C2 crosses (77.82 ±4.44) over the whole experimental period. The C2 crosses always recorded significantly higher breathing rate than the Cameroon except during the first High feeding phase (1 - 4 weeks) when the Cameroon recorded a higher value than the C2 crosses even if the difference between them was not significant. This is attributed to the sharp rise in breathing rate of the Cameroon during Week 2. Males (67.90 ±3.64) recorded lower breathing rate than females (80.07 ±3.83) over the whole experimental period and the difference between them was significant. Females always recorded higher values than males and significant differences between them over the whole experimental period are explained by significant differences during the Low and the second High phases (see Table 16).

The significant effect of genotype on breathing rate at 1200 hrs after six (6) hours of exposure to high ambient temperature (31°C/50%RH) was thus associated with the period of conditioning, with the Low phase of feeding during 5 - 8 weeks and with the second High feeding phase during 9 - 12 weeks. The significant effect of sex on the same trait was associated with the Low phase during 5 - 8 weeks and with the second High phase during 9 - 12 weeks.

The model explains 0.27 of the variation for breathing rate at 2000 hrs after two (2) hours of exposure to low ambient temperature (15°C/70%RH) over the whole experimental period. During the period of conditioning, 1 - 4 weeks, 5 - 8 weeks and 9 - 12 weeks, the model explains 0.41, 0.38, 0.32, and 0.25 of the variation for this trait. During the same period i. e. the overall period, period of conditioning, 1 - 4 weeks, 5 - 8 and 9 - 12 weeks, the coefficient of variation was 19.96%, 18.95%, 20.37%, 17.94% and 23.60%, respectively. Throughout this period the effect of genotype and sex on breathing rate per minute at 2000 hrs was not significant. It amounted to 19.31 ±1.95 for the Cameroon and 18.75 ±1.75 for the C2 crosses; 17.48 ±1.53 for the males and 21.36 ±1.63 for the females over the whole experimental period.

Fig. 10 shows the rectal temperature of the Cameroon lambs and the C2 (Cameroon X Mutton) crosses measured at 1200 hrs during the day at 31°C/50%RH ambient temperature. Rectal temperature of the Cameroon lambs measured at 1200 hrs during the day exhibited a decline from 1 - 4 weeks to 5 - 8 and 9 - 12 weeks. The C2 lambs recorded higher rectal temperature than the Cameroon genotype throughout all three feeding phases. The difference between both genotypes was much wider during 5 - 12 weeks i. e. during the Low phase (5 - 8 weeks) and during the second High phase (9 - 12 weeks). The decline in rectal temperature exhibited by C2 lambs was more gradual compared with the Cameroon.

Fig. 10 also shows the rectal temperature of the Cameroon lambs and the C2 (Cameroon X Mutton) crosses [page 64↓]measured at 2000 hrs and at 15°C/70%RH ambient temperature. Rectal temperature at 2000 hrs was higher for the Cameroon lambs than for the C2 crosses during every feeding phase. Rectal temperature measured at 2000 hrs exhibited a decline from 1- 4 weeks to 5 - 8 weeks after which it showed a slight rise from 5 - 8 weeks to 9 - 12 weeks. The largest difference in rectal temperature between the Cameroon and the C2 crosses was recorded during 5 - 8 weeks when consumption of concentrated feed was restricted to 1.5 times above maintenance level. The C2 crosses recorded lower rectal temperature at 2000 hrs than at 1200 hrs during 5 - 8 weeks, thus showing a different pattern of reaction influenced by feeding level.

Fig. 11: Effect of fluctuating temperatures (high and low during the day and at night, respectively) on breathing rate of Cameroon and Cameroon x Mutton lambs during the post-weaning growth phase

Fig. 11 shows the breathing rate of the Cameroon lambs and the C2 (Cameroon X Mutton) crosses measured at 1200 hrs during the day at 31°C/50%RH ambient temperature. Breathing rate measured at 1200 hrs was always higher for the C2 crosses compared with the Cameroon. The Cameroon exhibited a decline from 1- 4 weeks to 5 - 8 and 9 - 12 weeks. The C2 exhibited a slight increase during the same period. Large differences in breathing rate between the Cameroon and the C2 crosses occurred during 5 - 12 weeks i. e. during the Low feeding phase (5 - 8 weeks) and during the second High phase (9 - 12 weeks).

Fig. 11 also shows the breathing rate of the Cameroon lambs and the C2 (Cameroon X Mutton) crosses measured at 2000 hrs and at 15°C/70%RH ambient temperature. Neither genotype nor sex had any significant effect on breathing rate per minute measured at 2000 hrs. The Cameroon recorded a slightly higher value than the C2 crosses from 1 - 4 weeks to 5 - 8 weeks. After that, the Cameroon recorded a lower value during 9 - 12 weeks than the C2 crosses. It is hereby noted that towards the end of the twelve (12) week period under caged conditions, the lambs tended to be easily excited during the evening when ambient temperature was lower than during the day. They were often excited and therefore readily engaged in mock fights and this might have an effect on the quality of the measurements and especially of breathing rate.

5.4 Carcass evaluation

Carcass evaluation was done in order to measure productive performance as effected by various treatments in terms of absolute and relative weight of muscle, fat and bones of the seven selected valuable parts, as well as the effects of the same on carcass quality and the weight of the digestive organs, blood, coat and lungs.

5.4.1 Influence of different feeding levels on performance

The analysis of variance showing the effects of treatment, genotype and sex on carcass value is shown in Table 17. Corresponding means are shown in Table 18.

Carcass traits:The effect of treatment on warm and cold dressed weight was not significant. That of genotype was highly significant but that of sex was not. The model explains 0.73 of the variation. The coefficient of variation [page 65↓]was about 15% for both traits. The effect of treatment on cooling losses was not significant, that of genotype on the same was very significant whereas that of sex was not. Carcasses of the C1 and C2 crosses were significantly heavier than those of the Cameroon as expected. Differences between the crosses were not significant but the C2 weighed more than the C1. Cooling losses were significantly higher in the Cameroon than in the C1 and C2 crosses. The difference between the C1 and C2 crosses was not significant.

The effect of treatment on relative weight of each carcass part to the weight of the Right Half and on the relative weight of muscle, fat and bones to the weight of the carcass part from which they were dissected, was for the most part not significant except in the case of the weight of bones of the foreleg. The difference between High-Low and Low-High treatments was significant in favour of the former. Thus large differences in the type of feeding had largely no effect on the proportionate weight of muscle, fat and bones to the Right Half or the respective carcass parts.

Significant effects of genotype and sex on carcass traits reflected higher values of absolute weight of muscle and bones for the C2 crosses than for the C1 and the Cameroon and higher values for the males than for the females. The C1 crosses gained more fat than either C2 crosses or the Cameroon. Differences between the crosses (C1 and C2) were almost always significant. Males recorded a heavier weight of muscle and bones than females. In the case of absolute weight of fat, females recorded higher values than males, although the difference between them was not significant.

The effect of treatment on relative weight of each carcass part to the weight of the Right Half and on the relative weight of muscle, fat and bones to the weight of the carcass part from which they were dissected, was for the most part not significant except in the case of the weight of bones of the foreleg. The difference between the High-Low and the Low-High treatments was significant in favour of the former. Thus large differences in the type of feeding had largely no effect on the proportionate weight of muscle, fat and bones to the Right Half or the respective carcass parts.

Significant effects of genotype and sex on relative weight of each carcass part to the weight of the Right Half and on the relative weight of muscle, fat and bones to the weight of the carcass part from which they were dissected shows much variation as follows:

Carcass quality traits: Significant differences in carcass quality were recorded for light reflection score and fluid content. The effect of genotype on light reflection score was significant. The C2 crosses recorded significantly higher values than the C1 crosses. The effect of treatment, genotype and sex on fluid content was significant. Fluid content was significantly higher in the Low-High treatment than in the High-Low one, in the C1 than in both the Cameroon and the C2 crosses, and higher in the males than in the females.


[page 66↓]

Table 17: Results of ANOVA of absolute and relative weights of important parts of the carcass of lambs and of measures of carcass quality, 1995

 

Treatment

Genotype

Sex

  

Trait

DF

1

2

1

R-SQ

CV (%)

1. Carcass value

     

Warm carcass, kg

ns

***

ns

0.73

15.10

Cooling losses (%)

ns

**

ns

0.39

11.21

Dressing out %

ns

***

ns

0.44

3.91

Area of MLD (13th rib), cm2

ns

***

ns

0.70

15.02

2. Proportion to Right Half (%)

     

2.1 Carcass part: Right Half

     

Foreleg

ns

ns

ns

0.14

4.91

Back

ns

*

ns

0.33

5.03

Breast

ns

ns

ns

0.15

6.64

Hindleg

ns

*

*

0.36

3.59

Middle

ns

**

ns

0.40

7.38

Neck

ns

*

***

0.55

10.59

Thinning

ns

ns

ns

0.18

10.86

2.2 Muscle: Right Half

     

Foreleg

ns

*

ns

0.30

7.40

Back

ns

**

ns

0.45

6.52

Breast

ns

*

ns

0.27

12.93

Hindleg

ns

***

ns

0.55

4.76

Middle

ns

ns

ns

0.10

17.24

Neck

ns

***

***

0.68

10.89

Thinning

ns

ns

ns

0.08

18.97

2.3 Fat: Right Half

     

Foreleg

ns

***

ns

0.49

21.02

Back

ns

**

**

0.46

23.05

Breast

ns

*

*

0.29

22.84

Hindleg

na

***

*

0.52

18.45

Middle

ns

***

ns

0.62

22.51

Neck

ns

***

ns

0.51

13.30

Thinning

ns

*

ns

0.24

28.00

2.4 Bones: Right Half

     

Foreleg

*

ns

ns

0.29

12.28

Back

ns

ns

ns

0.24

10.60

Breast

ns

ns

ns

0.18

13.43

Hindleg

ns

ns

ns

0.09

10.26

Middle

ns

ns

ns

0.18

37.77

Neck

ns

ns

ns

0.23

31.51

*** p≤0.001; ** p≤0.01;* p≤0.05; ns for not significant


[page 67↓]

Continuation: Table 17

 

Treatment

Genotype

Sex

  

Trait

DF

1

2

1

R-SQ

CV (%)

3. Proportion to carcass part (%)

     

3.1.1 Muscle of foreleg: foreleg

ns

***

ns

0.50

4.59

3.1.2 Fat of foreleg: foreleg

ns

***

ns

0.45

22.70

3.1.3 Bones of foreleg: foreleg

*

ns

ns

0.23

11.23

3.2.1 Muscle of back: back

ns

***

**

0.54

5.48

3.2.2 Fat of back : back

ns

**

**

0.46

20.49

3.2.3 Bones of back: back

ns

*

ns

0.39

11.11

3.3.1 Muscle of breast: breast

ns

*

*

0.33

9.34

3.3.2 Fat of breast: breast

ns

*

*

0.31

22.15

3.3.3 Bones of breast: breast

ns

ns

ns

0.16

9.98

3.4.1 Muscle of hindleg: hindleg

ns

***

ns

0.62

2.64

3.4.2 Fat of hindleg: hindleg

ns

***

ns

0.49

20.04

3.4.3 Bones of hindleg: hindleg

ns

*

ns

0.32

7.37

3.5.1 Muscle of middle: middle

ns

ns

ns

0.12

15.44

3.5.2 Fat of middle: middle

ns

***

ns

0.59

21.15

3.5.3 Bones of middle: middle

ns

ns

ns

0.13

43.87

3.6.1 Muscle of neck: neck

ns

***

**

0.61

6.69

3.6.2 Fat of neck: neck

ns

***

**

0.56

20.60

3.6.3 Bones of neck: neck

ns

ns

ns

0.16

20.88

3.7.1 Muscle of thinning: thinning

ns

ns

ns

0.18

14.42

3.7.2 Fat of thinning: thinning

ns

ns

ns

0.18

26.96

4. Quality traits

     

Light reflection (Goefo)

ns

*

ns

0.70

4.88

pH for MLD, 1.5 hrs

ns

ns

ns

0.10

5.50

pH for MLD, 24 hrs

ns

ns

ns

0.22

4.74

pH for MSM, 1.5 hrs

ns

ns

ns

0.20

4.65

pH for MSM, 24 hrs

ns

ns

ns

0.16

4.50

Fluid content of muscle

*

*

*

0.44

10.37

5. Digestive organs, g

     

Intestinal tract

***

***

**

0.79

10.37

Intestines

***

***

**

0.73

14.49

Rumen

**

***

ns

0.55

13.80

Reticulum

**

***

ns

0.63

12.79

Omasum

ns

***

ns

0.49

17.47

Abomasum

**

***

*

0.72

15.47

Liver

***

***

ns

0.82

12.26

Pancreas

***

***

**

0.64

19.45

Pharynx

***

***

ns

0.60

14.97

6. Intestinal contents:full tract (%)

ns

*

ns

0.32

8.54

7. Organs of thermoregulation, g

     

Blood

*

***

ns

0.57

17.88

Coat

ns

***

ns

0.57

16.59

Lungs

*

***

*

0.67

15.57

*** p≤0.001; ** p≤0.01;* p≤0.05; ns for not significant


[page 68↓]

Table 18: Means and standard errors of absolute and relative weights of important parts of the carcass of lambs and of measures of carcass quality, 1995

 

Treatment

Genotype

Sex

 

High-Low

Low-High

Cameroon

C1

C2

Male

Female

Trait N:

15

15

10

10

10

14

16

1. Carcass value

       

Warm carcass, kg

11.92a ±0.85

12.86a ±0.89

8.63a ±0.45

13.47b ±0.89

15.07b ±0.28

12.00a ±0.92

12.72a ±0.82

Cold dressed weight, kg

11.54a ±0.83

12.43a ±0.86

8.32a ±0.44

13.06b ±0.87

14.59b ±0.28

11.61a ±0.90

12.31a ±0.81

Dressing out %

49.76a ±0.75

49.31a ±0.51

47.38a ±0.66

50.21b ±0.67

51.03b ±0.47

48.62a ±0.66

50.34a ±0.55

Area of MLD(13th rib), cm2

11.12a ±0.75

11.99a ±0.82

8.54a ±0.48

13.96b ±0.86

12.66b ±0.48

11.64a ±0.79(13)|

11.49a ±0.80(15)

2. Proportion to Right Half (%)

       

2.1 Carcass part: Right Half

       

Foreleg

16.86a ±0.23

16.60a ±0.19

16.92a ±0.21

16.36a ±0.34

16.92a ±0.18

16.81a ±0.28

16.66a ±0.15

Back

15.98a ±0.24

16.41a ±0.24

16.15a ±0.27

16.70b ±0.20

15.74a ±0.34

15.95a ±0.26

16.41a ±0.22

Breast

14.43a ±0.32

14.31a ±0.16

13.94a ±0.19

14.77a ±0.43

14.41a ±0.21

14.22a ±0.34

14.50a ±0.15

Hindleg

33.54a ±0.33

33.60a ±0.40

32.63a ±0.50

34.19b ±0.34

33.89a ±0.34

32.98a ±0.43

34.09b ±0.25

Middle

6.00a ±0.15

5.85a ±0.13

6.28a ±0.13

5.54b ±0.07

5.96a ±0.19

6.07a ±0.16

5.80a ±0.11

Neck

8.62a ±0.37

8.32a ±0.27

9.16a ±0.42

7.77b ±0.20

8.48a ±0.41

9.23a ±0.36

7.80b ±0.16

Thinning

4.57a ±0.14

4.91a ±0.13

4.93a ±0.15

4.67a ±0.21

4.61a ±0.14

4.74a ±0.14

4.74a ±0.14

2.2 Muscle: Right Half

       

Foreleg

11.19a ±0.30

11.29a ±0.17

10.82a ±0.18

11.01a ±0.37

11.88b ±0.19

11.31a ±0.32

11.18a ±0.17

Back

9.76a ±0.21

10.08a ±0.21

9.29a ±0.23

10.45b ±0.18

10.02a ±0.23

10.01a ±0.23

9.84a ±0.20

Breast

7.80a ±0.38

7.80a ±0.16

7.10a ±0.20

8.10b ±0.47

8.20b ±0.21

7.95a ±0.35

7.67a ±0.22

Hindleg

24.69a ±0.42

24.52a ±0.43

22.99a ±0.32

25.16b ±0.42

25.66b ±0.33

24.21a ±0.47

24.95a ±0.36

Middle

3.80a ±0.23

3.91a ±0.07

3.91a ±0.08

3.72a ±0.04

3.93a ±0.36

4.02a ±0.11

3.71a ±0.20

Neck

5.24a ±0.29

5.01a ±0.17

5.14a ±0.23

4.65a ±0.20

5.58b ±0.35

5.71a ±0.24

4.61b ±0.13

Thinning

2.99a ±0.15

3.19a ±0.14

2.99a ±0.17

3.18a ±0.20

3.10a ±0.18

3.16a ±0.12

3.03a ±0.17

2.3 Fat: Right Half

       

Foreleg

2.54a ±0.17

2.48a ±0.19

3.03a ±0.15

2.59a ±0.21

1.93b ±0.12

2.52a ±0.17

2.51a ±0.19

Back

3.12a ±0.28

3.40a ±0.20

3.71a ±0.26

3.43a ±0.33

2.64b ±0.22

2.93a ±0.19

3.55b ±0.26

Breast

4.05a ±0.33

4.03a ±0.19

4.48a ±0.29

4.02a ±0.39

3.62b ±0.23

3.71a ±0.24

4.32b ±0.27

Hindleg

3.15a ±0.24

3.48a ±0.18

3.79a ±0.21

3.52a ±0.25

2.64b ±0.18

3.15a ±0.20

3.46b ±0.22

Middle

0.80a ±0.08

0.74a ±0.06

1.02a ±0.06

0.74b ±0.06

0.55c ±0.04

0.83a ±0.08

0.72a ±0.05

Neck

1.53a ±0.10

1.80a ±0.15

2.10a ±0.15

1.60b ±0.12

1.29b ±0.11

1.68a ±0.17

1.65a ±0.10

Thinning

1.59a ±0.15

1.72a ±0.10

1.94a ±0.15

1.49b ±0.17

1.52b ±0.11

1.59a ±0.14

1.71a ±0.12

Means with different subscripts within rows are significantly different. Figures in brackets show changes in N


[page 69↓]

Continuation: Table 18

 

Treatment

Genotype

Sex

 

High-Low

Low-High

Cameroon

C1

C2

Male

Female

Trait
>N:

15

15

10

10

10

14

16

3. Proportion to carcass part (%)

       

3.1.1 Muscle of foreleg: foreleg

66.24a ±1.13

68.03a ±0.93

63.98a ±0.77

67.20b ±1.48

70.24c ±0.58

67.16a ±1.29

67.12a ±0.85

3.1.2 Fat of foreleg: foreleg

15.21a ±1.12

14.97a ±1.13

17.96a ±0.97

15.92a ±1.41

11.39b ±0.72

15.10a ±1.13

15.08a ±1.12

3.1.3 Bones of foreleg: foreleg

18.54a ±0.37

17.00b ±0.63

18.06a ±0.77

16.88a ±0.78

18.37a ±0.34

17.74a ±0.58

17.80a ±0.53

        

3.2.1 Muscle of back: back

61.16a ±1.31

61.48a ±1.11

57.61a ±1.42

62.68b ±1.43

63.67b ±0.65

62.77a ±1.00

60.06b ±1.26

3.2.2 Fat of back : back

19.33a ±1.55

20.64a ±1.11

22.88a ±1.33

20.39a ±1.82

16.68b ±1.17

18.30a ±1.11

21.46b ±1.41

3.2.3 Bones of back: back

19.51a ±0.75

17.88a ±0.42

19.50a ±0.77

16.93b ±0.57

19.65a ±0.72

18.93a ±0.43

18.49a ±0.77

        

3.3.1 Muscle of breast: breast

53.89a ±1.86

54.54a ±1.04

51.02a ±1.55

54.70a ±2.13

56.93b ±1.31

55.71a ±1.43

52.92b ±1.48

3.3.2 Fat of breast: breast

28.18a ±2.26

28.17a ±1.26

32.06a ±1.84

27.37b ±2.64

25.10b ±1.59

26.34a ±1.75

29.78b ±1.78

3.3.3 Bones of breast: breast

17.92a ±0.45

17.29a ±0.47

16.92a ±0.44

17.93a ±0.77

17.97a ±0.39

17.96a ±0.54

17.30a ±0.39

        

3.4.1 Muscle of hindleg: hindleg

73.58a ±0.74

72.94a ±0.78

70.50a ±0.64

73.57b ±0.65

75.72c ±0.60

73.36a ±0.68

73.17a ±0.82

3.4.2 Fat of hindleg: hindleg

9.44a ±0.76

10.39a ±0.56

11.62a ±0.65

10.33a ±0.77

7.79b ±0.54

9.62a ±0.66

10.17a ±0.68

3.4.3 Bones of hindleg: hindleg

16.98a ±0.33

16.67a ±0.40

17.88a ±0.49

16.10b ±0.38

16.49b ±0.22

17.02a ±0.21

16.66a ±0.45

        

3.5.1 Muscle of middle: middle

62.96a ±3.46

66.98a ±1.04

62.34a ±0.85

67.25a ±0.61

65.33a ±5.42

66.35a ±1.25

63.77a ±3.25

3.5.2 Fat of middle: middle

13.27a ±1.15

12.53a ±0.89

16.29a ±0.82

13.26b ±1.04

9.15c ±0.61

13.56a ±1.22

12.32a ±0.83

3.5.3 Bones of middle: middle

23.77a ±3.48

20.50a ±0.67

21.38a ±1.09

19.49a ±0.73

25.52a ±5.13

20.10a ±0.73

23.91a ±3.23

        

3.6.1 Muscle of neck: neck

60.72a ±1.76

60.33a ±1.37

56.28a ±1.58

59.71b ±1.53

65.60c ±1.36

62.10a ±1.77

59.16b ±1.30

3.6.2 Fat of neck: neck

18.16a ±1.44

21.37a ±1.43

23.06a ±1.50

20.76a ±1.70

15.50b ±1.39

18.12a ±1.58

21.20b ±1.32

3.6.3 Bones of neck: neck

21.12a ±1.27

18.30a ±0.71

20.67a ±2.02

19.53a ±1.00

18.93a ±0.55

19.78a ±1.46

19.65a ±0.69

        

3.7.1 Muscle of thinning: thinning

65.49a ±2.98

64.83a ±1.96

60.55a ±2.89

68.06a ±3.25

66.88a ±2.68

66.84a ±2.41

63.69a ±2.54

3.7.2 Fat of thinning: thinning

34.51a ±2.98

35.17a ±1.96

39.46a ±2.89

31.95a ±3.25

33.12a ±2.68

33.16a ±2.41

36.31a ±2.54


[page 70↓]

Continuation: Table 18

 

Treatment

Genotype

Sex

 

High-Low

Low-High

Cameroon

C1

C2

Male

Female

Trait
N:

15

15

10

10

10

14

16

4. Quality traits

       

Light reflection (Goefo)

62.80a ±2.48

64.40a ±1.75

.

61.00a ±1.45

66.20b ±2.01

63.50a ±3.07

63.67a ±1.61

pH for MLD, 1.5 hrs

5.97a ±0.09

6.02a ±0.08

6.03a ±0.08

5.88a ±0.11

6.08a ±0.11

6.03a ±0.08

5.96a ±0.09

pH for MLD, 24 hrs

5.70a ±0.07

5.61a ±0.08

5.50a ±0.09

5.69a ±0.09

5.77b ±0.07

5.68a ±0.07

5.63a ±0.08

pH for MSM, 1.5 hrs

5.86a ±0.07

5.95a ±0.08

5.96a ±0.08

5.81a ±0.11

5.95a ±0.08

5.99a ±0.08

5.83a ±0.06

pH for MSM, 24 hrs

5.59a ±0.07

5.61a ±0.06

5.48a ±0.08

5.67a ±0.07

5.66a ±0.09

5.63a ±0.06

5.57a ±0.07(15)

Fluid content of muscle

0.42a ±0.02

0.46b ±0.01

0.41a ±0.02

0.48b ±0.01

0.43a ±0.01

0.45a ±0.01

0.43b ±0.01

        

5. Digestive organs, g

       

Intestinal tract

1210.87a ±55.88

1441.20b ±75.11

1043.00a ±50.75

1451.60b ±78.51

1483.50b ±157.60

1342.07a ±70.22

1312.00b ±74.57

Intestines

604.93a ±37.62

741.53b ±45.70

511.20a ±31.16

741.80b ±51.45

766.70b ±41.28

698.07a ±40.32

651.50b ±48.47

Rumen

391.93a ±15.24

461.27b ±22.64

359.30a ±16.35

463.80b ±31.15

456.70b ±11.96

420.14a ±23.68

432.25a ±19.29

Reticulum

66.67a ±2.94

75.47b ±3.90

57.40a ±2.81

77.20b ±3.13

78.60b ±3.62

70.50a ±4.20

71.56a ±3.14

Omasum

57.27a ±3.57

59.27a ±3.39

47.10a ±2.16

69.40b ±3.47

58.30c ±3.53

57.93a ±3.15

58.56a ±3.72

Abomasum

85.80a ±6.31

103.07b ±6.23

70.10a ±5.17

99.20b ±5.60

114.00c ±6.28

95.14a ±6.16

93.81b ±7.02

Liver

304.47a ±14.94

421.87b ±24.12

286.90a ±17.88

364.50b ±28.35

438.10c ±25.16

352.14a ±25.93

372.81a ±24.74

Pancreas

34.80a ±2.42

46.40b ±3.14

32.20a ±2.53

41.80b ±4.14

47.80b ±3.27

42.36a ±3.27

39.06b ±3.09

Pharynx

204.53a ±9.86

252.67b ±12.81

191.60a ±9.02

231.50b ±14.67

262.70b ±14.98

220.36a ±12.05

235.81a ±13.55

6. Intestinal contents:full tract (%)

59.02a ±1.49

56.61a ±1.36

54.04a ±2.27

58.95b ±1.11

60.45b ±1.06

58.21a ±1.77

57.47a ±1.16

7. Organs of thermoregulation, g

       

Blood

1028.53a ±61.74

1203.53b ±78.06

887.40a ±55.34

1113.30b ±87.86

1347.40c ±55.92

1084.64a ±81.62

1143.50a ±66.82

Coat

1620.00a ±105.77

1814.87a ±98.77

1325.50a ±74.85

1933.20b ±116.79

1893.60b ±84.25

1694.40a ±105.72

1737.60a ±104.77

Lungs

248.27a ±17.08

278.20b ±16.56

212.60a ±13.56

250.80b ±12.69

326.30c ±17.49

267.07a ±17.76

259.88b ±16.80

Means with different subscripts within rows are significantly different. Figures in brackets show changes in N


[page 71↓]

Digestive organs: The model explains 0.49 - 0.82 of the variation. The coefficient of variation was about 10 - 20% for these traits. The effect of treatment on the weight of the digestive organs was very dramatic as is reflected in the very significantly to highly significantly heavier weight of the intestinal tract, intestines, rumen, reticulum, abomasum, liver, pancreas and pharynx of the Low-High treatment compared with the High-Low one. The effect of genotype on the weight of the same was highly significant. The C1 and C2 crosses recorded highly significant weight of intestinal tract, intestines, rumen, reticulum, pancreas and pharynx than the Cameroon. The difference between the C1 and C2 crosses was not significant. The C1 crosses recorded significantly heavier weight of omasum than the Cameroon and the C2 crosses.

The difference between the Cameroon and the C2 crosses was significant in favour of the latter. The C2 crosses recorded significantly heavier weight of abomasum and liver than the Cameroon and the C1 crosses. The difference between the Cameroon and the C1 crosses was significant in favour of the former. Thus differences due to genotype were largely dictated by differences in live body weight. The effect of sex on weight of intestinal tract, intestines, abomasum and pancreas was significant in favour of the males.

Blood, coat and lungs: The effect of treatment on weight of blood was significant, that of genotype highly significant, and that of sex not significant. The Low-High treatment recorded significantly more weight of blood than the High-Low one. The C1 and C2 crosses recorded significantly more than the Cameroon. The difference between the C1 and C2 crosses was significant in favour of the latter. The effect of treatment on the weight of coat was not significant, that of genotype was highly significant, and that of sex was not significant. The C1 and C2 crosses recorded a significantly heavier weight of coat than the Cameroon. The difference between the C1 and C2 crosses was not significant. The effect of treatment on the weight of lungs was significant, that of genotype highly significant, and that of sex, significant. The C1 and C2 crosses recorded significantly heavier weight of lungs than the Cameroon. The difference between the C1 and C2 crosses was significant in favour of the latter.

5.4.2 Reaction to high ambient temperature during the day and of alternating feeding levels

The objective was to quantify the amount of muscle, fat and bones as well as the carcass quality of slaughtered male and female Cameroon lambs and C2 (Cameroon X Mutton) male and female crossbred lambs following exposure of all lambs to the above mentioned single treatment. Maximum wheat straw intake per lamb per day was limited to 200g.

The analysis of variance showing the effects of treatment, genotype and sex on carcass value is shown in Table 19. Corresponding means are shown in Table 20.

Carcass traits: The effect of genotype on warm and cold dressed weight was very significant and highly significant, respectively. The effect of sex on both traits was very significant. In both cases the model explains 0.90 of the variation. The coefficient of variation was about 11% for warm carcass and 10% for cold dressed weight.

Significant effects of genotype and sex on carcass traits reflected higher values of absolute weight of muscle and bones for the C2 crosses than for the Cameroon and higher values for the males than for the females.

In the case of absolute weight of fat, a significant difference between the Cameroon and the C2 crosses was recorded for fat in the foreleg. Significant differences in absolute weight of fat between males and females were higher in the former. Thus males tended to develop significantly more muscle, fat and bones than females.

Significant effects of genotype and sex on relative weight of each carcass part to the weight of the Right Half and on the relative weight of muscle, fat and bones to the weight of the carcass part from which they were dissected shows much variation as follows:


[page 72↓]

Table 19: Results of ANOVA of absolute and relative weights of important parts of the carcass of lambs and of measures of carcass quality, 1996

 

Genotype

Sex

  

Trait

DF:

1

1

R-SQ

CV (%)

1. Carcass value

    

Warm carcass, kg

**

**

0.90

10.71

Cooling losses (%)

ns

ns

0.62

21.73

Dressing out %

ns

ns

0.30

3.88

Area of MLD(13th rib), cm2

*

*

0.63

12.61

2. Proportion to Right Half (%)

    

2.1 Carcass part: Right Half

    

Foreleg

*

ns

0.56

3.69

Back

*

ns

0.59

5.64

Breast

ns

ns

0.08

6.80

Hindleg

**

*

0.84

2.81

Middle

ns

*

0.60

7.40

Neck

***

ns

0.83

7.60

Thinning

ns

ns

0.14

16.61

2.2 Muscle: Right Half

    

Foreleg

ns

ns

0.37

5.91

Back

*

ns

0.45

6.93

Breast

ns

ns

0.18

6.85

Hindleg

***

*

0.86

4.46

Middle

ns

ns

0.26

11.31

Neck

*

**

0.79

5.76

Thinning

***

ns

0.85

7.56

2.3 Fat: Right Half

    

Foreleg

ns

ns

0.06

23.76

Back

*

ns

0.58

13.77

Breast

ns

ns

0.21

27.82

Hindleg

*

ns

0.54

18.55

Middle

ns

ns

0.45

26.66

Neck

***

ns

0.85

13.64

Thinning

ns

ns

0.05

33.42

*** p≤0.001; ** p≤0.01;* p≤0.05; ns for not significant; DF Degrees of freedom


[page 73↓]

Continuation: Table 19

 

Genotype

Sex

  

Trait

DF:

1

1

R-SQ

CV (%)

2.4 Bones: Right Half

    

Foreleg

ns

ns

0.29

14.73

Back

ns

ns

0.12

9.10

Breast

ns

ns

0.25

11.76

Hindleg

ns

ns

0.04

8.93

Middle

ns

ns

0.10

20.43

Neck

ns

ns

0.39

32.67

3. Proportion to carcass part (%)

    

3.1.1 Muscle of foreleg: foreleg

ns

ns

0.03

3.68

3.1.2 Fat of foreleg: foreleg

ns

ns

0.07

24.89

3.1.3 Bones of foreleg: foreleg

ns

ns

0.26

13.42

     

3.2.1 Muscle of back: back

ns

ns

0.06

4.53

3.2.2 Fat of back : back

ns

ns

0.37

12.13

3.2.3 Bones of back: back

*

ns

0.59

7.99

     

3.3.1 Muscle of breast: breast

ns

ns

0.20

10.32

3.3.2 Fat of breast: breast

ns

ns

0.25

22.53

3.3.3 Bones of breast: breast

ns

ns

0.37

10.54

     

3.4.1 Muscle of hindleg: hindleg

**

ns

0.80

2.35

3.4.2 Fat of hindleg: hindleg

*

ns

0.64

19.29

3.4.3 Bones of hindleg: hindleg

ns

ns

0.38

7.50

     

3.5.1 Muscle of middle: middle

ns

ns

0.12

6.36

3.5.2 Fat of middle: middle

ns

ns

0.19

29.90

3.5.3 Bones of middle: middle

ns

ns

0.05

16.95

     

3.6.1 Muscle of neck: neck

**

ns

0.70

6.93

3.6.2 Fat of neck: neck

*

ns

0.62

13.16

3.6.3 Bones of neck: neck

ns

ns

0.25

25.34

     

3.7.1 Muscle of thinning: thinning

ns

ns

0.45

14.37

3.7.2 Fat of thinning: thinning

ns

ns

0.45

15.44

*** p≤0.001; ** p≤0.01;* p≤0.05; ns for not significant; DF Degrees of freedom


[page 74↓]

Continuation: Table 19

 

Genotype

Sex

  

Trait

DF:

1

1

R-SQ

CV (%)

4. Quality traits

    

PH for MLD, 1.5 hrs

ns

ns

0.14

4.60

PH for MLD, 24 hrs

ns

ns

0.04

1.88

PH for MSM, 1.5 hrs

ns

ns

0.39

3.95

PH for MSM, 24 hrs

*

ns

0.46

1.11

Fluid content of muscle

ns

ns

0.26

8.76

     

5. Digestive organs, g

    

Intestinal tract

**

*

0.80

15.06

Intestines

*

ns

0.67

19.85

Rumen

**

*

0.77

13.48

Reticulum

**

ns

0.77

18.33

Omasum

**

*

0.80

17.38

Abomasum

***

*

0.90

12.96

Liver

*

**

0.73

16.62

Pancreas

*

*

0.69

18.00

Pharynx

**

*

0.81

13.36

6. Intestinal contents:full tract (%)

ns

ns

0.37

20.21

7. Organs of thermoregulation, g

    

Blood

***

**

0.94

8.00

Coat

***

*

0.91

9.21

Lungs

**

*

0.84

10.65

*** p≤0.001; ** p≤0.01;* p≤0.05; ns for not significant; DF Degrees of freedom


[page 75↓]

Table 20: Means and standard errors of absolute and relative weights of important parts of the carcass of lambs and of measures of carcass quality, 1996

 

Genotype

Sex

 

Cameroon

C2

Male

Female

Trait
N:

5

5

6

4

1. Carcass value

    

Warm carcass, kg

9.31a ±1.10

14.42b ±1.15

13.16a ±1.15

8.43b ±1.53

Cooling losses (%)

3.22a ±0.25

2.15a ±0.39

2.46a ±0.32

3.31a ±0.42

Dressing out %

47.83a ±0.96

49.34a ±0.76

49.06a ±0.60

47.40a ±1.54

Area of MLD (13th rib), cm2

10.42a ±0.69

12.74b ±0.94

12.48a ±0.80

10.22b ±0.87

2. Proportion to Right Half, %

    

2.1 Carcass part: Right Half

    

Foreleg

16.28a ±0.37

17.37b ±0.16

16.65a ±0.39

17.08a ±0.31

Back

17.50a ±0.50

15.65b ±0.24

16.66a ±0.56

16.45a ±0.66

Breast

13.77a ±0.27

13.87a ±0.51

14.00a ±0.32

13.55a ±0.51

Hindleg

31.35a ±0.63

34.29b ±0.59

32.04a ±0.69

33.98b ±1.05

Middle

6.72a ±0.25

6.24a ±0.33

6.83a ±0.22

5.96b ±0.24

Neck

9.75a ±0.26

7.44b ±0.37

8.87a ±0.52

8.19a ±0.83

Thinning

4.63a ±0.15

5.15a ±0.46

4.96a ±0.41

4.79a ±0.15

2.2 Muscle: Right Half

    

Foreleg

10.95a ±0.27

11.70a ±0.32

11.16a ±0.33

11.57a ±0.34

Back

10.74a ±0.30

9.67b ±0.30

10.20a ±0.43

10.22a ±0.26

Breast

7.44a ±0.26

7.34a ±0.20

7.24a ±0.22

7.62a ±0.16

Hindleg

22.09a ±0.54

26.08b ±0.76

23.29a ±0.91

25.27b ±1.38

Middle

4.43a ±0.15

4.24a ±0.29

4.52a ±0.20

4.06a ±0.21

Neck

5.08a ±0.26

4.56b ±0.17

5.12a ±0.19

4.36b ±0.09

Thinning

2.14a ±0.08

2.88b ±0.08

2.48a ±0.16

2.55a ±0.27

2.3 Fat: Right Half

    

Foreleg

2.64a ±0.30

2.60a ±0.23

2.51a ±0.20

2.78a ±0.36

Back

3.94a ±0.20

3.02b ±0.21

3.54a ±0.23

3.39a ±0.42

Breast

4.07a ±0.50

4.05a ±0.56

4.46a ±0.44

3.46a ±0.52

Hindleg

3.54a ±0.16

2.54b ±0.30

3.12a ±0.33

2.92a ±0.35

Middle

0.98a ±0.17

0.81a ±0.07

1.02a ±0.11

0.70a ±0.11

Neck

2.32a ±0.15

1.34b ±0.06

1.91a ±0.25

1.70a ±0.28

Thinning

2.49a ±0.14

2.27a ±0.46

2.47a ±0.34

2.24a ±0.31

Means with different subscripts within rows are significantly different. Figures in brackets show changes in N.


[page 76↓]

Continuation: Table 20

 

Genotype

Sex

 

Cameroon

C2

Male

Female

Trait
N:

5

5

6

4

3. Proportion to carcass part (%)

    

3.1.1 Muscle of foreleg: foreleg

67.25a ±0.74

67.32a ±1.29

67.01a ±1.02

67.69a ±0.99

3.1.2 Fat of foreleg: foreleg

16.22a ±1.84

14.99a ±1.45

15.09a ±1.16

16.38a ±2.40

3.1.3 Bones of foreleg: foreleg

16.54a ±1.42

17.70a ±0.55

17.90a ±0.45

15.94a ±1.69

     

3.2.1 Muscle of back: back

61.39a ±0.95

61.78a ±1.41

61.12a ±0.82

62.28a ±1.70

3.2.2 Fat of back : back

22.48a ±0.69

19.28a ±1.36

21.17a ±0.97

20.45a ±1.88

3.2.3 Bones of back: back

16.13a ±0.45

18.94b ±0.72

17.72a ±1.03

17.27a ±0.34

     

3.3.1 Muscle of breast: breast

54.14a ±2.35

53.29a ±2.79

51.89a ±2.25

56.47a ±2.34

3.3.2 Fat of breast: breast

29.41a ±3.15

28.83a ±3.18

31.69a ±2.54

25.26a ±3.01

3.3.3 Bones of breast: breast

16.45a ±1.07

17.88a ±0.63

16.43a ±0.84

18.27a ±0.77

     

3.4.1 Muscle of hindleg: hindleg

70.45a ±0.55

76.01b ±1.02

72.58a ±1.40

74.21a ±1.81

3.4.2 Fat of hindleg: hindleg

11.33a ±0.68

7.44b ±0.93

9.86a ±1.20

8.68a ±1.21

3.4.3 Bones of hindleg: hindleg

18.21a ±0.43

16.55a ±0.66

17.57a ±0.54

17.11a ±0.92

     

3.5.1 Muscle of middle: middle

66.03a ±1.84

67.82a ±1.86

66.12a ±1.60

68.13a ±2.19

3.5.2 Fat of middle: middle

14.42a ±2.26

13.16a ±1.43

15.05a ±1.58

11.89a ±2.01

3.5.3 Bones of middle: middle

19.55a ±1.61

19.02a ±1.14

18.83a ±1.19

19.97a ±1.65

     

3.6.1 Muscle of neck: neck

52.12a ±2.45

61.39b ±0.99

58.19a ±1.66

54.60a ±4.48

3.6.2 Fat of neck: neck

23.78a ±1.57

17.97b ±0.48

21.15a ±1.71

20.46a ±2.03

3.6.3 Bones of neck: neck

24.11a ±3.39

20.64a ±1.40

20.66a ±1.59

24.95a ±3.87

     

3.7.1 Muscle of thinning: thinning

46.28a ±1.66

57.32a ±4.17

50.79a ±3.04

53.32a ±5.88

3.7.2 Fat of thinning: thinning

53.72a ±1.66

42.68a ±4.17

49.21a ±3.04

46.68a ±5.88

     

4. Quality traits

    

pH for MLD, 1.5 hrs

6.11a ±0.11

5.93a ±0.13

6.00a ±0.11

6.05a ±0.14

pH for MLD, 24 hrs

5.40a ±0.05

5.38a ±0.04

5.40a ±0.04

5.38a ±0.06

pH for MSM, 1.5 hrs

6.07a ±0.10

5.76a ±0.10

5.94a ±0.13

5.88a ±0.10

pH for MSM, 24 hrs

5.29a ±0.03

5.19b ±0.02

5.23a ±0.03

5.26a ±0.04

Fluid content of muscle

0.44a ±0.02

0.40a ±0.02

0.42a ±0.01

0.42a ±0.03


[page 77↓]

Continuation: Table 20

 

Genotype

Sex

 

Cameroon

C2

Male

Female

Trait
N:

5

5

6

4

5. Digestive organs, g

    

Intestinal tract

962.20a ±52.37

1515.60b ±140.79

1356.50a ±166.70

1062.50b ±121.03

Intestines

493.60a ±49.43

727.80b ±78.29

678.33a ±82.59

509.25a ±54.25

Rumen

360.80a ±26.70

494.80b ±45.80

474.67a ±39.61

357.50b ±41.91

Reticulum

51.40a ±4.96

87.80b ±7.85

75.83a ±10.92

60.25a ±8.54

Omasum

49.60a ±5.05

78.00b ±9.52

73.67a ±8.85

49.00b ±6.65

Abomasum

67.00a ±4.09

125.40b ±9.56

104.67a ±16.12

83.50b ±12.32

Liver

299.00a ±30.27

387.80b ±48.50

396.67a ±29.78

263.50b ±36.42

Pancreas

38.00a ±3.42

53.80b ±5.86

51.33b ±5.08

37.75b ±5.22

Pharynx

199.00a ±20.97

290.00b ±22.08

271.67a ±26.85

203.75b ±23.35

6. Intestinal contents:full tract (%)

46.55a ±7.62

59.89a ±1.22

55.67a ±3.01

51.8a3 ±8.71

7. Organs of thermoregulation, g

    

Blood

797.00a ±66.78

1266.40b ±103.42

1219.20a ±130.95

856.00b ±100.39

Coat

1414.80a ±132.27

2231.00b ±87.50

1965.67a ±174.69

1608.75b ±280.95

Lungs

209.20a ±11.10

300.80b ±21.82

276.33a ±24.64

223.00b ±25.69

Means with different subscripts within rows are significantly different. Figures in brackets show changes in N

For relative weight of each carcass part to the weight of the Right Half the C2 crosses recorded significantly and very significantly higher proportion of foreleg and hindleg, respectively, than the Cameroon. The Cameroon recorded significantly and highly significantly higher proportion of weight of back and neck, respectively, than the C2 crosses. Females recorded a higher proportion of hindleg than the males, and the males, a higher proportion of middle than the females.

Carcass quality traits: The effect of genotype and sex on most carcass quality traits considered was not significant except in the case of pH value of the MSM 24 hours post-mortem for which the Cameroon recorded a significantly higher value than the C2 crosses.

Digestive organs: The model explains 0.67 - 0.90 of the variation for weight of digestive organs. The coefficient of variation was about 13 - 20%. For weight of all the digestive organs considered, the C2 crosses recorded significantly to highly significantly heavier weights than the Cameroon. The males recorded significantly to very significantly heavier weight than the females for all digestive organs except the intestines and the reticulum.

Blood, coat and lungs: The effect of genotype on weight of blood was highly significant, and that of sex, very significant. The effect of genotype on weight of coat was highly significant, and that of sex, significant. The effect of genotype on weight of lungs was very significant, and that of sex, significant. The C2 crosses recorded significantly heavier weight than the Cameroon, and the males significantly heavier than the females.

5.4.3 Distribution of internal fat in response to different levels of feeding under stall temperature conditions (1995) and high ambient temperature during the day with alternating feeding levels (1996)

Table 21 shows the analysis of variance and means and standard errors of relative and absolute fat of the carcasses with regard to total fat∗, internal fat (kidney fat and mesenteric fat together), kidney and mesenteric fat. The distribution of this fat has been referred to under each treatment as follows:

Influence of different feeding levels on performance: The effect of treatment on the proportion of total fat to dead weight was not significant under stall ambient temperature conditions. The effect of genotype on the same was significant and that of sex, very significant. The model explains 0.41 of the variation for this trait. The coefficient was 20.59%. The Cameroon had a significantly higher proportion of this fat than the C1 and C2 crosses. The difference between the C1 and C2 crosses was not significant. The difference between the males and the females was significant in favour of the latter.

Treatment did not effect the proportion of kidney and mesenteric fat significantly. The effect of genotype on the proportion of kidney fat was highly significant and that of sex, significant. The Cameroon had a significantly higher proportion than the C1 and C2 crosses. The difference between the C1 and C2 crosses was not significant. The difference between the males and the females was significant in favour of the latter.

The effect of genotype on the proportion of mesenteric fat was significant and that of sex was very significant. The Cameroon and the C2 crosses recorded a significantly higher value than the C1 crosses. The difference between the Cameroon and the C2 crosses was not significant. The difference between the males and the females was significant in favour of the latter.

Reaction to high ambient temperature during the day and of alternating feeding levels: The effect of genotype on the proportion of mesenteric fat was very significant and that of sex was not. The model explains 0.75 of the variation for this trait. The coefficient of variation was 13.98%. The Cameroon had a significantly higher proportion than the C2 crosses. The difference between the males and the females was significant but males recorded a higher value this time than the females. A similar reaction can be seen in the case of the proportion of kidney and mesenteric fat.

Looking at the absolute values, it can be seen that under the temperature treatment, large differences between the Cameroon and the C2 crosses occurred with regard to kidney fat, and that those between the males and females occurred with regard to mesenteric fat (see Table 21).

The amount of fat stored in the kidney and in the stomach and intestines following High-Low and Low-High feeding where both treatments were characterised by a similar level and length of feed restriction shows low levels of coefficient of determination for both kidney and mesenteric fat. The Low feeding phase therefore tended to limit the amount of internal fat deposited. Nevertheless, Low-High feeding tended to raise the amount of internal fat deposited compared High-Low feeding.


[page 79↓]

Table 21: Results of ANOVA of relative deposition of total fat*, kidney and mesenteric fat of slaughtered lambs by treatment, genotype and sex in 1995 and 1996

Experiment

Influence of different feeding levels

Reaction to high ambient temperature during ther day and alternating feeding levels

1. Total fat: D-wt**

DF

p 0.05

1. Total fat: D-wt**

DF

p 0.05

Treatment

1

ns

Treatment

N/A

N/A

Genotype

2

*

Genotype

1

**

Sex

1

**

Sex

1

ns

R-SQ

 

0.41

R-SQ

 

0.75

CV(%)

 

20.59

CV(%)

 

13.98

2. Internal fat: D-wt

DF

p 0.05

2. Internal fat: D-wt

DF

p 0.05

Treatment

1

ns

Treatment

N/A

N/A

Genotype

2

**

Genotype

1

***

Sex

1

**

Sex

1

ns

R-SQ

 

0.46

R-SQ

 

0.92

CV(%)

 

24.46

CV(%)

 

12.46

3. Kidney fat: D-wt

DF

p 0.05

3. Kidney fat: D-wt

DF

p 0.05

Treatment

1

ns

Treatment

N/A

N/A

Genotype

2

***

Genotype

1

***

Sex

1

*

Sex

1

ns

R-SQ

 

0.54

R-SQ

 

0.91

CV(%)

 

23.63

CV(%)

 

14.91

4. Mesenteric fat: D-wt

DF

p 0.05

4. Mesenteric fat: D-wt

DF

p 0.05

Treatment

1

ns

Treatment

N/A

N/A

Genotype

2

*

Genotype

1

***

Sex

1

**

Sex

1

ns

R-SQ

 

0.42

R-SQ

 

0.88

CV(%)

 

26.53

CV(%)

 

14.63

*** p 0.001/0.0001 or less; ** p 0.01;* p 0.05; ns for not significant. Means with different subscripts within rows are significantly different. Figures in brackets show the size of N; NB : ** Dead weight, D-wt, is defined here as fasting weight less intestinal contents and blood; *Total fat does not include fat in the head and feet

The C2 deposited the highest amount of kidney fat followed by the Cameroon and lastly the C1. The C2 crosses also deposited the highest amount of mesenteric fat followed by the C1 and then lastly the Cameroon. Again females tended to deposit more kidney and mesenteric fat than the males.


[page 80↓]

The Low phase of feeding therefore had the effect of narrowing the difference in the deposition of internal fat between the treatments and the genotypes and sexes. Nevertheless, the trend for the C2 crosses to deposit more internal fat than the C1 crosses and for the females to deposit more than the males is obvious.

In the temperature treatment, the amount of kidney fat deposited by the pure Cameroon was significantly higher than that by the C2 crosses. The amount of mesenteric fat also tended to be higher in the Cameroon than in the C2 crosses although the difference between them was not significant. Compared with the situation under stall ambient temperature conditions, males deposited a relatively higher amount of kidney fat and a significantly higher amount of mesenteric fat than the males in absolute terms.


[page 81↓]

Table 22: Relative means and standard errors reflecting the pattern of deposition of total fat, kidney and mesenteric fat of slaughtered lambs by treatment, genotype and sex in 1995 and 1996.

   

Mean ±se

Trait

  

Treatment

Genotype

Sex

Relative weight (%)

Year

Experiment

1

2

Cameroon

C1

C2

Male

Female

1. Total fat:
D-wt**

1995

Influence of different feeding levels

9.63a
±0.73(15)

9.94a
±0.53(15)

11.24a
±0.70µ

8.98b
±0.88µ

9.14b
±0.53µ

8.82a
±0.58(14)

10.63b
±0.60(16)

 

1996

Reaction to high ambient temperature during the day and of alternating feeding levels

N/A

N/A

11.99a
±0.55¯

N/A

8.20b
±0.70°

10.14a
±1.25°

9.57a
±1.07¯

          

2. Internal fat:
D-wt

1995

Influence of different feeding levels

4.85a
±0.44(15)

5.02a
±0.36(15)

5.87a
±0.44µ

3.96b
±0.49µ

4.98b
±0.34µ

4.31a
±0.39(14)

5.48b
±0.35(16)

 

1996

Reaction to high ambient temperature during the day and of alternating feeding levels

N/A

N/A

6.67a
±0.29¯

N/A

3.37b
±0.26°

4.83a
±0.97°

4.84a
±0.81¯

          

3. Kidney fat:
D-wt

1995

Influence of different feeding levels

1.69a
±0.16(15)

1.98a
±0.14(15)

2.30a
±0.18µ

1.46b
±0.15µ

1.74b
±0.14µ

1.65a
±0.16(14)

1.99b
±0.14(16)

 

1996

Reaction to high ambient temperature during the day and of alternating feeding levels

N/A

N/A

2.48a
±0.08¯

N/A

1.16b
±0.13°

1.62a
±0.35°

1.79a
±0.36¯

          

4. Mesenteric fat: D-wt

1995

Influence of different feeding levels

3.16a
±0.29(15)

3.04a
±0.23(15)

3.57a
±0.28µ

2.50b
±0.36µ

3.24a
±0.23µ

2.66a
±0.25(14)

3.49b
±0.23(16)

 

1996

Reaction to high ambient temperature during the day and of alternating feeding levels

N/A

N/A

4.20a
±0.22¯

N/A

2.21b
±0.21°

3.13a
±0.62°

3.05a
±0.46¯

*** p 0.001/0.0001 or less; ** p 0.01;* p 0.05; ns for not significant. Means with different subscripts within rows are significantly different. Figures in brackets show the size of N
NB : ** Dead weight, D-wt, is defined here as fasting weight less intestinal contents and blood
*Total fat does not include fat in the head and feet


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