THE FUNCTIONAL-SIGNIFICANCE OF THE BROWSER-GRAZER DICHOTOMY IN AFRICAN RUMINANTS

The allometric relationships for the fermentation rate of dry matter, the total energy concentration of volatile fatty acids (VFAs), the ene rgy supplied from VFA production and the mass of the digesta contents within the rumen or caecum and proximal colon (hindgut) were used to t est whether the digestive strategies of grazing and browsing African r uminants differ. The wet and dry mass of the contents of the rumen and hindgut were allometrically related to body mass (BM). These relation ships did not differ between browsing and grazing ruminants. The ferme ntation rates in the rumen were strongly allometric and the intercepts of the relationships did not differ between browsers and grazers. The fermentation rates in the hindgut were not allometrically related to BM and did not differ between ruminants with different feeding habits. Likewise, the total energy concentration of the VFAs in the rumen and hindgut showed no allometric scaling and did not differ between brows ing and grazing ruminants. The energy supplied by VFA production in bo th the rumen and hindgut of African ruminants scaled at around 0.8 wit h BM. Only in the case of the energy supplied by VFAs in the rumen wer e there significantly different intercepts for browsing and grazing ru minants. The energy supplied by VFA production in the rumen was inadeq uate to meet the energy requirements for maintenance of browsers and s mall grazers. The retention time of digesta in the alimentary tract wa s positively related to BM although there was no difference in the all ometric relationships for grazers and browsers. The results of these a nalyses suggest that, after controlling for the effects of body mass, there is little difference in digestive strategy between African rumin ants with different morphological adaptations of the gut.