Awgichew, Kassahun: Comparative performance evaluation of Horro and Menz sheep of Ethiopia under grazing and intensive feeding conditions

Institut für Nutztierwissenschaften
der Landwirtschaftlich-Gärtnerischen Fakultät
der Humboldt-Universität zu Berlin


Dissertation
Comparative performance evaluation of Horro and Menz sheep of Ethiopia under grazing and intensive feeding conditions

Zur Erlangung des akademischen Grades
doctor rerum agriculturarum (Dr. rer. agr.)

eingereicht an der Landwirtschaftlich-Gärtnerischen Fakultät
der Humboldt-Universität zu Berlin

von Kassahun Awgichew,
(M.Sc., Animal Science, University of Wales, UK)

Präsident der Humboldt-Universität zu Berlin
Prof. Dr. Jürgen Mlynek

Dekan der Landwirtschaftlich-Gärtnerischen Fakultät
Prof. Dr. Dr. h. c. E. Lindmann

Gutachter:
Vorsitzender der Prüfungskommission Prof. Dr. Konrad Hagedorn
Prof. Dr. K. J. Peters
Prof. Dr. G. Seeland

weitere Mitglieder der Prüfungskommission
Dr. Claudia Kijora
Dr. T. Hardge

Tag der mündlichen Prüfung: 20. 12. 2000

Zusammenfassung

Die vorliegende Untersuchung wurde am International Livestock Centre for Africa (ILCA), jetzt International Livestock Research Institute (ILRI) auf der Versuchsstation Debre Birhan in Äthiopien durchgeführt. Diese Untersuchung ist Teil eines panafrikanischen ILRI-Forschungsprogramms zur Untersuchung und Charakterisierung einheimischer kleiner Wiederkäuer im Sub-Saharischen Afrika auf genetische Resistenz gegenüber Endoparasiten. Das Ziel dieser Arbeit bestand darin, Ergebnisse zu verschaffen, die zum Verständnis der relativen Leistung zweier äthiopischer Hochlandschafrassen (Horroschaf und Menzschaf) unter Stationsbedingungen dienen sollen.

Horro-Lämmer (2,43±0,03 kg) waren signifikant (p<0,001) schwerer als Menz-Lämmer (2,17±0,03 kg). Außerdem beeinflußten auch die anderen Haupteffekte wie Geschlecht, Wurfgröße, Wurfnummer und Geburtssaison signifikant das Geburtsgewicht. Lämmer, die von zu Beginn der Regenzeit angepaarten Schafen geboren wurden, hatten tendenziell höhere Geburtsgewichte als solche, deren Mütter während der Trockenzeit angepaart wurden. Dies könnte auf die damit verbundene Verfügbarkeit von relativ besserem Futter hinsichtlich Qualität und Quantität während der Trächtigkeitsdauer der Mutterschafe zurückzuführen sein.

Wurfgröße, Wurfnummer und Geburtssaison hingegen beeinflußten signifikant (p<0,01) die durchschnittlichen Tageszunahmen bis zum Absetzen. Von der Geburt bis zum Alter von 30 Tagen nahmen männliche Einzellämmer 114,01±2,70 g zu, Zwillingslämmer 71,2±4,63 g; Zwischen Geburt und Absetzen (90 Tage postpartum) lagen die Tageszunahmen bei 82,42±1,85 g für die einzeln geborenen und bei 55,75±3,34 g für die Zwillingslämmer.

Die Überlebensrate der Lämmer innerhalb der ersten beiden Wochen nach der Geburt wurde deutlich von der Wurfgröße, Wurfnummer und der Geburtssaison beeinflußt, jedoch nicht von der Rasse und dem Geschlecht. Mehr als 97 % der einzeln geborenen Lämmer überlebten bis zum Alter von 15 Tagen, bei den Zwillingslämmern jedoch nur 91 %. Desgleichen war die Überlebensrate von aus zweiten Würfen stammenden Lämmern (97 %) deutlich (p<0,001) höher als die aus ersten Würfen stammenden Lämmern (92 %). Nach dem Absetzen im Alter von ca. 90 Tage, zeigten die Menzlämmer eine deutlich höhere Überlebensrate als die Horrolämmer. Dies könnte auf Adaptationsprobleme bei den Horroschafen hinweisen, da diese von einer anderen Region des Landes gebracht wurden.

Bei den Körpermaßen konnten keine signifikanten Unterschiede im Brustumfang zwischen Horro- und Menzschafen festgestellt werden. Jedoch war die Widerristhöhe von Horrolämmern (61,91±0,62 cm) deutlich größer (p<0,001) als die von Menzlämmern (59,89±0,44 cm). Es konnte eine enge und signifikante Beziehung zwischen dem Körpergewicht und den linearen Körpermaßen, die in dieser Arbeit untersucht wurden, über alle Wachstumsstadien hinweg festgestellt wird. Es geht hervor, daß das Körpergewicht von beiden Rassen im Alter von einem Jahr ziemlich genau anhand des Brustumfangs geschätzt werden kann (Horro: r=0,91; Menz: r=0,90).

Der Ausschlachtungsanteil von Menzlämmern war in der Tendenz höher (p>0,05) als der von Horrolämmern. Ebenso tendenziell höher, aber statistisch nicht signifikant, war bei den Menzlämmern die geschätzte zerlegbare Fleischmasse (8,91±0,22 kg) im Vergleich zu den Horrolämmern (8,55±0,19 kg). Der Verfettungsgrad wurde sowohl direkt (durch Zerlegen) als auch indirekt (durch Ätherextraktion) geschätzt. Beide Rassen zeigten eine ziemlich ähnliche Körperfettverteilung. Jedoch lag der Schätzwert für die Ätherextraktion auf Trockenmassebasis beim Fleisch von Menzlämmern (22,4±0,89 %) deutlich über dem von Horrolämmern (18,1±1,00 %). Dies könnte ein Indiz dafür sein, daß das Fleisch von Menzschlachtkörpern mehr inter- und intramuskuläres Fett enthält als das von Horroschlachtkörpern. Angesichts des höheren Ausschlachtungsgrades, des höheren Anteils an intramuskulärem Fett und dem relativ höheren Fleisch : Knochen-Verhältnis scheint das Menzschaf unter den gegebenen Versuchsbedingungen

Schlagwörter:
Schafe, Rasse, Lämmer, Körpergewicht, Körpermasseentwicklung, Überlebensrate, lineare Körpermaße, Schlachtleistung, Körperfettverteilung, Ätherextraktion

Abstract

This study has been carried out at the former International Livestock Centre for Africa (ILCA), that is now the International Livestock Research Institute (ILRI) experiment station at Debre Birhan, Ethiopia. This research is part of an ILCA (now ILRI) Pan-African research programme designed to investigate and characterise genetic resistance to endoparasites in some indigenous small ruminants in sub-Saharan Africa. The present study was, therefore, undertaken in an attempt to generate information that may contribute towards the understanding of the relative performance of two highland sheep (Horro and Menz) of Ethiopia under station management conditions.

Horro lambs were significantly heavier (P <0.001) at birth than Menz lambs (2.43 ± 0.03 kg vs 2.17 ± 0.03 kg, respectively). Apart from breed, the other main effects which have influenced birth weight significantly (P <0.001) are sex, type of birth, dam parity and season of birth. Lambs born in the dry season from ewes mated at the beginning of the wet season tended to be heavier at birth than those born from ewes mated in the dry season. While there was no significant difference in weaning weight between Menz and Horro lambs (8.03 ± 0.12 kg vs 8.21 ± 0.13 kg, respectively), sex, birth type, dam parity and season of birth have all significantly (P <0.001) influenced weaning weight. Sex, birth type and season of birth remained to be significant sources of variation in body weight of male lambs of both breeds until one year of age. Single born male lambs gained 114.62 ± 2.58 g and 82.42 ± 1.85 g daily between birth and 30, birth and 90 days of age, respectively. The corresponding figures for twin born male lambs are 71.71 ± 4.53 g and 55.75 ± 3.34 g, respectively.

Lamb survival within two weeks of birth was strongly influenced by birth type, dam parity, and season of birth but not by breed and sex. More than 97 % of single born lambs survived to 15 days of age compared to 91 % for twins (P < 0.001). Likewise more (97 %) lambs born to second parity ewes survived to 15 days after birth as opposed to about 92 % for lambs born from ewes of first parity (P <0.001). The survival rate between birth and weaning (90 days) for Menz lambs (89 %) was significantly (P < 0.001) higher than that for the Horro (76 %). Menz lambs had also a much better post-weaning survival rate from birth to 180, 270 and 365 days of age (81, 71 and 62 %, respectively) compared to Horro (51, 39 and 37 %, respectively). This shows that Horro lambs might have adaptation problems as they are introduced from a different region of the country.

Horro lambs were taller (P < 0.001) at withers at one year of age compared to Menz (61.91 ± 0.62 cm vs 59.89 ± 0.44 cm). From what is observed in this study, body weight at one year of age for both breeds could be fairly accurately estimated from heart girth (r = 0.90 for Menz and r = 0.86 for Horro).

At the end of a 123 days fattening period, Horro lambs were significantly heavier (P < 0.05) than Menz lambs (34.7 ± 0.63 kg vs 32.7 ± 0.57 kg). While no significant difference (P > 0.05) was observed in rate of weight gain during the fattening period (45.5 ± 2.90 g for Menz and 47.3 ± 3.81 g for Horro). The dry matter intake of both breeds based on metabolic body weight (kg W0.75), 67.8 ± 1.95 g for Horro lambs and 65.6 ± 1.72 g for Menz, was not significantly different (P > 0.05).

Menz lambs tended to have a better but not significantly different (P > 0.05) dressing % than the Horro (49 % vs 48.0 %). Fat deposition was estimated directly (by dissection) and indirectly (through ether extraction). The two breeds have fairly similar body fat distribution. However, lean from Menz lamb carcasses had significantly higher (P < 0.01) ether extract estimate on dry matter bases compared to that of the Horro (22.4 ± 0.89 % vs 18.1 ± 1.00 % respectively). This is probably an indication showing that lean from Menz carcasses has more inter- and intramuscular fat than lean from Horro carcasses. Menz lambs also tended to have a better (P < 0.05) lean : bone ratio compared to Horro lambs (2.9 : 1 vs 2.7 :1, respectively). Considering the dressing percentage values, the higher proportion of intramuscular fat as indicated by a higher ether extract estimate of the lean part and a relatively higher lean : bone ratio, Menz lambs seem to be a relatively better meat breed compared to the Horro under the given experimental conditions. However more detailed studies need to be carried out for a conclusive result.

Keywords:
sheep, breed, lamb, bodyweight, growth rate, survival rate, linear body measurements, carcass performance, fat deposition, body fat distribution, Ether extract


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Table of Contents

Front pageComparative performance evaluation of Horro and Menz sheep of Ethiopia under grazing and intensive feeding conditions
Dedication
Acknowledgements
Abbreviations List of Abbreviations
1 INTRODUCTION
2 LITERATURE REVIEW
2.1Approaches to animal genetic resource evaluation
2.2Importance of small ruminant genetic resources in sub-Saharan Africa
2.3Birth weight, lamb weight development and average daily weight gain (ADG)
2.3.1Birth weight
2.3.2Lamb weight development and average daily weight gain (ADG)
2.4Lamb survival rate
2.5Linear body measurements
2.6Fattening performance of Tropical sheep breeds
2.6.1Carcass characteristics and composition
2.6.2Feed intake and fat deposition in small ruminants
2.6.3Feed influence on development of non-carcass tissues
3 MATERIAL AND METHODS
3.1Experimental location and climate
3.2Soil and vegetation
3.3Breeds and management
3.3.1Description of the local breeds used
3.3.2Mating
3.4Experimental design and data collection
3.4.1Grazing management
3.4.2Supplementary feeding and health care:
3.4.3Measurements
3.4.3.1Body weight and linear body measurements
3.4.3.2Feeding experiment
3.4.3.3Carcass evaluation
3.4.4Laboratory chemical determination
3.5Methods of statistical analysis
4 RESULTS AND DISCUSSION
4.1Lamb performance traits
4.1.1Weight development from birth to weaning (90 days)
4.1.2Average daily weight gain (ADG)
4.1.3Lamb survival rate
4.2Linear body measurements and their relation to body weight changes
4.3Fattening performance of male lambs
4.3.1Weight gain and feed intake of male Menz and Horro lambs
4.3.2Carcass performance and body fat estimate of Male Horro and Menz lambs
4.3.2.1Relative weights of carcasses and non-carcass components and dressing percentage
4.3.2.2Direct and indirect estimation of total body fat
4.4Discussion
4.4.1Birth weight
4.4.2Weaning weight, growth and average daily live weight gain (ADG)
4.4.3Lamb survival rate
4.4.4Fattening performance, feed intake and weight gain
4.4.5Relative weight of carcass and non-carcass components and dressing percentage
4.4.6Fat deposition characteristics
4.4.7Fat depot distribution in Menz and Horro lambs
5 Conclusion and recommendations of this study
6 SUMMARY
7 ZUSAMMENFASSUNG
Bibliography BIBLIOGRAPHY
Appendix A APPENDICES
A.1Appendix 9.1: ANOVA table for birth weight and preweaning growth performance of Horro and Menz lambs.
A.2Appendix 9.2: ANOVA table for preweaning and postweaning average daily weight gain (ADG) of Horro and Menz lambs to 180 days of age.
A.3Appendix 9.3: ANOVA table for growth performance of male Horro and Menz lambs from birth to one year of age.
A.4Appendix 9.4: ANOVA table for preweaning and postweaning average daily weight gain (ADG) of male Horro and Menz lambs to one year of age.
A.5Appendix 9.5: ANOVA table for body weight and linear body measurements of male Horro and Menz lambs at 180 days of age.
A.6Appendix 9.6: ANOVA table for body weight and linear body measurements of male Horro and Menz lambs at 270 days of age.
A.7Appendix 9.7: ANOVA tables for body weight and linear body measurements of male Horro and Menz lambs at 365 days of age.
A.8Appendix 9.8: Maximum-Likelihood analysis of variance table for survival rates at various ages
A.9Appendix 9.9: ANOVA tables for fattening and carcass performance of male Horro and Menz lambs at 365 days of age.
Declaration

Table of Tables

Table 1: Sheep population and production estimates for some sub-Saharan African countries1
Table 2: Estimate of annually slaughtered sheep and carcass yield per animal in some selected sub-Saharan African countries1
Table 3: Annual sheep productivity dynamics (Delta %) in some East African countries*
Table 4: Growth performance of some African and other sheep breeds and crosses under field and station management conditions
Table 5: Average daily weight gain (ADG) of some African other sheep breeds and crosses under field and station management conditions
Table 6: Survival rate of some African and other sheep breeds and crosses under field and station management conditions
Table 7: Means of body weight (kg) and linear body measurements (cm) of various tropical and temperate sheep breeds
Table 8: Carcass tissue proportions for various Temperate and Tropical sheep breeds and crosses
Table 9: Fresh weight of sheep non-carcass organs by breed or breed crosses and body weight
Table 10: Distribution of sires, ewes and lambs born by breed and season of birth
Table 11: Number and types of carcass and non-carcass samples analysed
Table 12: Body weight (kg) of Menz and Horro lambs from birth to 180 days of age
Table 13: Body weight (kg) of male Menz and Horro lambs from 120 to 365 days of age
Table 14: Average daily gain (ADG) of Menz and Horro lambs from birth to 180 days of age
Table 15: Average daily gain (ADG) of male Menz and Horro lambs from birth to 365 days of age
Table 16: Survival rate of Menz and Horro lambs from birth to 365 days of age
Table 17: Linear body measurements of male Menz and Horro lambs at 180 days of age
Table 18: Linear body measurements of male Menz and Horro lambs at 270 days of age
Table 19: Linear body measurements of male Menz and Horro lambs at 365 days of age
Table 20: Correlation coefficients of body weight and linear body measurements for male Menz and Horro lambs at 6 months of age (n=129 and 67 respectively)
Table 21: Regression models for predicting body weight of Menz and Horro ram lambs from some linear body measurements (HG, WH, BL, TC, TW)* at 180 days of age
Table 22: Correlation coefficients of body weight and body linear measurements for male Menz and Horro lambs at 9 months of age (n=174 and 83 respectively)
Table 23: Regression models for predicting body weight of Menz and Horro ram lambs from some linear body measurements (HG, WH, BL, TW, TC)* at 270 days of age
Table 24: Correlation coefficients of body weight and body linear measurements for male Menz and Horro lambs at 12 months of age (n=150 and 71 respectively)
Table 25: Regression models for predicting body weight of Menz and Horro ram lambs from some linear body measurements (HG, WH, BL, TL, TW, TC)* at 365 days of age
Table 26: Weight and body linear measurements of Male Menz and Horro lambs during the fattening period
Table 27: Fattening and carcass performance of Male Menz and Horro lambs
Table 28: Fresh weight of different parts of the gastro-intestinal tract (GIT) from male Menz and Horro lambs
Table 29: Feed intake and digestibility estimate of male Menz and Horro lambs during fattening period
Table 30: Least Squares Means (± SE) of estimated whole carcass components and proportion of whole carcass parts from male Menz and Horro lambs
Table 31: Least Squares Means and SE of carcass composition of the dissected left half carcasses from male Menz and Horro lambs
Table 32: Lean /bone and lean/fat ratio of whole and dissected half carcasses
Table 33: Least Squares Means ± SE of Ether extract estimate (g) of whole carcasses and non-carcass body components of Menz and Horro lambs
Table 34: Correlation of tail volume measurements, body fat depots and total body fat and Ether extract estimates
Table 35: Regression equations relating tail and rump fat weight (g) to tail volume measured on live animal (ml) and skinned tail volume (ml) taken after slaughter
Table 36: Regression equations relating estimated total disectable body fat (g) to tail volume measured on live animal (ml) and tail/rump fat weight (g) and skinned tail volume (ml) taken after slaughter

Table of Figures

Figure 1: Body weight of Menz and Horro lambs from birth to 180 days of age (LSM ± SE)
Figure 2: Body weight of male Menz and Horro lambs from birth to 365 days of age (LSM ± SE)
Figure 3: Body weight of Menz and Horro lambs from birth to 180 days of age by sex (LSM ± SE)
Figure 4: Body weight (LSM ± SE) of male Menz and Horro lambs from birth to 365 days of age by season of birth
Figure 5: Average daily weight gain, ADG of Menz and Horro lambs between birth and 180 days of age (LSM ± SE)
Figure 6: LSM ± SE of Average daily weight gain (ADG) of male Menz and Horro lambs between birth and 365 days of age
Figure 7: Deviation in average daily body weight gain (ADG) of male Menz and Horro lambs between various stages of growth from birth (Constant = LS overall mean)
Figure 8: Survival rate of Menz and Horro lambs to various stages of growth
Figure 9: Deviation of linear body measurements (cm) from overall LS means for male Menz and Horro lambs at 180 days of age
Figure 10: Deviation of linear body measurements (cm) from overall LS means for male Menz and Horro lambs at 365 days of age
Figure 11: Carcass composition of the dissected left half carcasses of Menz and Horro lambs
Figure 12: Carcass and non-carcass fat distribution of male Menz lambs
Figure 13: Carcass and non-carcass fat distribution of male Horro lambs

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