Diet Selection And Nutrition Of Sheep (Ovis Aries Linnaeus) And Grant’s Gazelles (Gazella Granti Brooke) On Kapiti Ranch, Kenya
Kilonzo, Joseph M
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A study was conducted to determine seasonal diet selection and nutritional characteristics of sheep and Grant’s gazelles on Kapiti ranch in southeastern Kenya The frequency and biomass production ot herbaceous plants were determined in dry and wet season by using the plot method Absolute and relative densities of woody plants on the site were determined using the point-centred quarter (PCQ) method. The dietary botanical composition of the study animal species was determined by using the microhistological technique Relative density was used as an estimate of the dry weight composition of each forage species in the diets of each animal species Plant species in the animal species’ diets were categorized into grass, forb and browse forage classes. Shannon- Wiener and Morisita's similarity indices were used to express diet diversity and overlap respectively, between the two animal species Diets were simulated based on microhistology results by weighting plant species corresponding to their relative densities in the diets to give 50 gm samples. These were then analysed for crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose, acid detergent lignin (ADL), and in vitro dry matter digestibility (IVDMD). Diet analyses indicated that sheep were predominantlv grazers during wet and dry season while Grant’s gazelles were mixed 'eeders, with a higher preference tor grasses during the wet season and an equal preference for both grasses and browse during the dry season. The forbs component was of little consequence for the two species.. Sheep mostly preferred Themeda triandra. Digitana macrob/ephara, Penmsetum meziamim, Pennisetum stramineum and Cyrtodon dactylon during the wet and dry season. Grant s gazelles showed high preference for Balanites aegyptiaca, Hibiscus flaw Johns, Acacia drepanolobmm, and Themeda triandra during the two seasons Diet diversity based on forage-class revealed that the diets of Grant’s gazelles were more diverse than those of sheep during the wet and dry season This implies that Grant’s gazelles can adopt their diets to change in vegetation at Athi Kapiti plains more than sheep. Degree of dietary overlap between the animal species was highest during the wet season when there were plenty of forage plants available for the two animal species There was a positive correlation between the ranked orders of preference of shared plant species that constituted their diets during the two seasons, but it was strong only during the dry season. There were significant differences (P<0.05) in dietary nutrient components between the animal species within seasons IVDMD was significantly higher (P<0.05) for both animal species during the wet season. It was 67.9% for sheep and 82.6% for Grant s gazelles during the wet season while during the dry season it was 54.9% for sheep and 67.2% for Grant’s gazelles On the other hand, NDF, ADF, ADL and cellulose were significantly higher (P<0.05) during the dry season. The NDF, .ADF, .ADL values were 64.8%, 38 2% and 4.4% and 53.4%, 32.5% and 7.1% for Sheep and Grant’s gazelles, respectively during the wet season. During the dry season the values were 74.5%, 47 5%, 6.7% and 61.6%, 37.4%, 9.6% for sheep and Grant’s gazelles respectively. Sheep diets were significantly higher (P<0.05) in CP (5.8%) in the wet season, whereas it was significantly higher (P<0.05) in the diets of Grant’s gazelles (8.1%) during the dry season The X1U nutrient components in the diets selected by the animal species showed that the sheep were dependent on grasses and that Grant’s gazelles were mixed feeders, able to use both grasses and browse. The CP (4 2%) and IVT)MD (54 9%) values were below the requirements for maintenance of sheep during the dry season. Protein supplementation in form of browse material and pods from Acacia species found in the ranch is thus recommended as a means of improving the diet quality and digestibility for sheep This will in turn improve sheep production and efficient utilization of range forage. Based on the findings of this study, it can be recommended that the two animal species be integrated on the same range because of the differences in diet selection and nutrition The Grant’s gazelles relied on a wide range of plant species selected firom the three forage classes as compared to sheep which relied much on the grass species. On the basis of their browsing activities, they are able to suppress woody plants, resulting in an environment that favours establishment of the herb layer (grass and forbs), which is favourable for sheep Therefore common use grazing involving these two ruminants is ecologically feasible. The integration ot the two ruminants can therefore make unique and important contributions to food production and income generation opportunities in areas with similar vegetation to that of Athi Kapiti plains.
University of Nairobi
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