Behrend, , Anke: Kinetik des Ingestaflusses bei Rehen (Capreolus capreolus) und Mufflons (Ovis ammon musimon) im saisonalen Verlauf

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Kapitel 6. Summary

The digestibility of slowly fermentable/digestible plant material increases with increasing particle retention time in the forestomach of ruminants. The retention time in the gastro-intestinal-tract depends on the size of the fermentation chambers, the food intake, the saliva flow and the selective retention of food particles. The mean retention time (MRT) of fluid and particles should differ between ruminant species and, according to differences in food quality and availability, between seasons. By measuring the ingesta passage rate of roe deer, a concentrate selector, in comparison with mouflon, a grass and roughage eater, adaptation factors of these different species to the seasonally changing forage supply were investigated.

A prerequisite for the trials was the habituation of the wild animals to the human investigator. Four roe deer fawns and five mouflon lambs were hand-raised with a commercial milk replacer. Rumen fistulas were implanted in all adult animals leading to the dorsal ruminal chamber. The animals were kept in adequate enclosures with natural vegetation. Roe deer fawns and mouflon lambs of two age classes were bottle-fed with a fluid marker (Cr-EDTA); monthly, for 15 months, a fluid (Co-EDTA) and a particle (Cr-mordanted fibre) marker were applied to all adult animals via the rumen fistula. After marker application, faecal samples were collected every 4 hours for 5 days. Faecal samples were prepared according to a newly developed method with sulphuric acid. The Co- and Cr-concentrations were measured by atomic absorption spectrophotometry. The retention time of fluid and particle phase in the gastro-intestinal-tract were calculated according to Thielemans et al. (1978), Grovum und Williams (1973) und Lechner-Doll (1990).

Such investigations were carried out for the first time under natural conditions comparing roe deer (n = 2) and mouflons (n = 5), and yielded the following results:

  1. In young animals, the ingestion of plant material and the daily faecal volume increased with increasing age up to the point of weaning, leading to a reduction of ingesta retention time distal of the reticulorumen.
  2. The total retention time of fluid and particles in the gastro-intestinal-tract was, for roe deer (MRTfluid GIT = 18,1 ± 2,4 h, MRTpart.GIT = 23,6 ± 3,8 h) shorter than for mouflon (MRTfluid GIT = 22,5 ± 3,9 h, MRTpart.GIT = 36,0 ± 4,2 h ) during the whole year. The particle retention time in the reticulorumen was for roe deer MRTpart.RR = 13,9 ± 3,1 h and for mouflon MRTpart.RR = 24,8 ± 3,0 h. Fluid remained in the reticulorumen of roe deer for MRTfluid RR = 8,0 ± 1,0 h and of mouflon for MRTfluid RR = 11,5 ± 2,0 h.
  3. For both species, the ingesta retention time in the gastro-intestinal-tract showed significant seasonal fluctuations. They were shorter during autumn, when the animals showed an increased food intake, and longer in winter due to a reduction in both metabolic rate and ingestion of forage of low digestibility.

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  4. Roe deer had a smaller selectivity factor (the quotient of particle reticulorumen retention time over fluid reticulorumen retention time) (SF = 1,55 ± 0,16) than mouflon (SF = 2,1 ± 0,29). This indicates that roe deer reduce the food particle size more efficiently during initial ingestion than mouflon, and that the forestomach particle retention is less selective in roe deer because of a less prominent (or absent) ingesta stratification.
  5. The fluid volume of the reticulorumen of roe deer was smaller than that of mouflon.
  6. The content of indigestible material in the gastro-intestinal-tract and the daily faecal volume increased for both roe deer and mouflon during late summer and autumn and were constant during the rest of the year.
  7. The concentrations of short-chain fatty acids varied according to both time of day and season, depending on food intake and composition. The molar proportions typical for concentrate selectors and grass and roughage eaters could be demonstrated for both species.

Roe deer are, in contrast to mouflon, more limited in their capacity to digest cellulose-containing plants due to the short particle retention times in the reticulorumen. Because the ingesta is retained only shortly in roe deer in spring and summer, there is not sufficient time for cellulose fermentation, even though cellulolytic enzymes are available in sufficient amounts. On the other hand, cellulose fermentation is limited in winter by the scarcity of cellulolytic enzymes in spite of a prolonged ingesta retention. Longer particle retention time in the reticulorumen of mouflon provides favourable conditions for cellulose fermentation in all seasons. The seasonally variable ingesta retention times in the gastro-intestinal-tract are an expression of the adaptation capacities of both species to the seasonally fluctuating food supply.


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