The functional anatomy of the alimentary tract of Thomson's gazelle (gazella thomsonii Gunther" 1884), with special reference to the stomach

Abstract

Thomson's gazelle and the related species have been described. Three areas consisting of the Loroghi and Kapiti plains and Elmenteita were chosen to represent the habitat of this species in Kenya. The first two areas were overgrazed by domestic livestock while Elmenteita was selected to demonstrate the feeding behaviour of thomsonii in the absence of overstocking and deteriorating range conditions. The vegetation of the study areas was described. It was observed that in the wet season Thomson's gazelle was a pure grazer, preferring only grass leaf. During this period the selectivity of diet was minimal, the variance ratio was 98 + 1.73 S.D. However, in the dry season the available pasture herbage and dicotyledon forbs became scarce and the animals had to spend more time picking bits here and there. Consequently, the variance ratio increased to 58 ± 19 S.D. The grass components consumed included,sheath (2,0%) and stem (15%) and a little fraction of leaf (3%). Statistical analysis revealed that protein digestibility is related to faecal N in the organic matter (OM). The average percentage of organic matter digestibility of the forage and the nitrogen content in the faeces of thomsonii revealed a general decline in the dry season. Thus, the regression coefficient could be used to determine approximately the digestibility of the forage. Two animals, a male and a female Thomsonts gazelle, were fixed with formalin in the standing position and dissected in order to show the topographical situation of the stomach. This was necessary in describing the parts and their function. Finally, the histology of the rumen epithelium was investigated and any structural variation exterpolated in terms of the season. It was observed that there were changes in the micropapillary body which could be related to either dry or wet season. Generally in the dry season the micropapillary body was poorly developed at the same time when the papillae regressed. The wet season showed long and broad papillae with a thick or high epithelium and little keratinization.