Forage intake and nutritive value of sheep and goat diets in South-eastern Kenya

Abstract

The forage intake, botanical composition and nutritive value of diets selected by free-ranging sheep and goats grazing together in south-eastern Kenya were determined. Forage intake was estimated using chromium sesquioxide orally administered daily to the animals. Dietary botanical composition was determined using the microhistological faecal analysis technique, whereas quality of simulated diet samples was determined by chemical analysis for crude protein, neutral detergent fibre, acid detergent fibre, lignin, total ash and in vitro dry and organic matter digestibilities. Dry matter intake in gjday was similar (P > 0.05) for sheep and goats within a given season, but in terms of metabolic bodyweight (gjkg WO.7S), it was significantly lower (P < 0.05) for goats compared to sheep during the dry season. Dry matter intake averaged 471.3 gjday or 2% of bodyweight and 500.3 gjday or 2.5% of bodyweight for goats and sheep, respectively. The lowest levels of intake for both species (1.6% for goats and 2.0% for sheep) were recorded during the wet season. Overall, sheep consumed 53.0 gjkg WO·7S while goats had an average intake of 43.6 gjkg WO·7S• Goats selected diets that were higher (P < 0.05) in crude protein than did sheep i.e 16. 4% and 13. 5% , respecti vel y when averaged across the two seasons. Sheep diets had lower (P < 0.05) levels of lignin during the wet season compared to goats but the lignin contents for both were the same during the dry season. Goats, however, selected diets lower in neutral detergent fibre and acid detergent fibre than did sheep. Goats were found to be better adapted for survival in this environment than sheep. In vitro dry matter digestibility of simulated diets were not different between goats and sheep i.e 56.2% and 55.6%, respectively. In vitro organic matter digestibility also did not differ between the two livestock species i.e 55.1% and 56.5% for goats and sheep, respectively. Digestibility coefficients of the diets of both animal species were significantly higher (P < 0.05) for the wet season than the dry season diets. Goats' diets consisted mainly of browse (> 81%) while those of sheep comprised mainly grasses (> 77%) during both seasons. Goats consumed very_little forbs (> 2%) whereas browse was the least utilized forage category by sheep « 8%). Neither species showed significant change (P > 0.05) in the proportions of grass, forbs or browse in their diets with change of season, and no single plant dominated the diets of either livestock species. Sheep and goats were therefore complimentary in their feeding in both seasons.