im saisonalen Verlauf - Kora

6 SummaryThe digestibility of slowly fermentable/digestible plant material increases withincreasing particle retention time in the forestomach of ruminants. The retentiontime in the gastro-intestinal-tract depends on the size of the fermentationchambers, the food intake, the saliva flow and the selective retention of foodparticles. The mean retention time (MRT) of fluid and particles should differbetween ruminant species and, according to differences in food quality andavailability, 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 foragesupply were investigated.A prerequisite for the trials was the habituation of the wild animals to the humaninvestigator. Four roe deer fawns and five mouflon lambs were hand-raised with acommercial milk replacer. Rumen fistulas were implanted in all adult animalsleading to the dorsal ruminal chamber. The animals were kept in adequateenclosures with natural vegetation. Roe deer fawns and mouflon lambs of two ageclasses were bottle-fed with a fluid marker (Cr-EDTA); monthly, for 15 months, afluid (Co-EDTA) and a particle (Cr-mordanted fibre) marker were applied to alladult animals via the rumen fistula. After marker application, faecal samples werecollected every 4 hours for 5 days. Faecal samples were prepared according to anewly developed method with sulphuric acid. The Co- and Cr-concentrations weremeasured by atomic absorption spectrophotometry. The retention time of fluid andparticle phase in the gastro-intestinal-tract were calculated according toThielemans et al. (1978), Grovum und Williams (1973) und Lechner-Doll (1990).Such investigations were carried out for the first time under natural conditionscomparing 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 faecalvolume increased with increasing age up to the point of weaning,leading to a reduction of ingesta retention time distal of thereticulorumen.2. The total retention time of fluid and particles in the gastro-intestinaltractwas, for roe deer (MRT fluid GIT = 18,1 ± 2,4 h, MRT part.GIT = 23,6± 3,8 h) shorter than for mouflon (MRT fluid GIT = 22,5 ± 3,9 h,MRT part.GIT = 36,0 ± 4,2 h ) during the whole year. The particleretention time in the reticulorumen was for roe deer MRT part.RR = 13,9± 3,1 h and for mouflon MRT part.RR = 24,8 ± 3,0 h. Fluid remained inthe reticulorumen of roe deer for MRT fluid RR = 8,0 ± 1,0 h and ofmouflon for MRT fluid RR = 11,5 ± 2,0 h.3. For both species, the ingesta retention time in the gastro-intestinaltractshowed significant seasonal fluctuations. They were shorterduring autumn, when the animals showed an increased food intake,and longer in winter due to a reduction in both metabolic rate andingestion of forage of low digestibility.96