Rumen fermentation and food selection in East African sheep, goats, Thomson's gazelle, Grant's gazelle and impala

Abstract

The relationship between the selected food and rumen fermentation was investigated in Thomson's gazelle, Grant's gazelle, impala and Maasai haired sheep and goats. All animals were shot in the same grass-bushland area within 1 week during the dry season.According to rumen contents, sheep were almost exclusively grazers. In goats, Thomson's gazelle and impala, grass accounted for about 70% of all plant parts identified. In Grant's gazelle, browse includingAcaciaseed constituted 68% of rumen ingesta. The two gazelle species showed a very marked preference for green grass leaves.In sheep and goat rumens, concentrations of NH₃-N and volatile fatty acids, andin vitrofermentation rates (262 and 272 μmoles gas_NTPD/g D.M./h, respectively) were lowest. In the wild ruminants, concentrations of fermentation end-products were higher and the rate of fermentation significantly (P< 0·05) faster, namely 420 in Thomson's gazelle, 356 in Grant's gazelle and 376 in impala. Rumen pH was not significantly different between species, with mean values ranging between 6·3 and 6·0. Total VFA concentrations ranged between 124 and 178 m-equiv/1 in the rumen and around 25 m-equiv/1 in the abomasum. Acetic acid accounted for about 75% of the total VFAs.It is concluded that there are large differences in the pattern of rumen fermentation between wild and domestic mixed-feeding ruminants which reflect their respective food preferences.