NUTRITION OF BISONS (BISON BISON), CAMELS (CAMELUS BACTRIANUS), AND HORSES (EQUUS CABALLUS) AT THEIR JOINT GRAZING IN AN ISOLATED STEPPE PASTURE

摘要

The nutrition of free-ranging bisons (Bison bison), house horses (Equus caballus), and camels (Camelus bactrianus) were investigated at their joint grazing on a forb-grass steppe pasture. The species composition of the consumed plants, the selectivity of food plants, and the digestibility of plant forage were assessed. Species of the consumed plants and their share in the diet were determined using the microhistologic analysis of feces. The plant food selectivity was estimated by the ratio of the share of plant species in the diet of animals to their portion in the plant community of the pasture. The digestibility is calculated by the ratio of inert (undigested) components (silicon, lignin) in the diet and feces. In summer (June), these characteristics in horses and bisons were similar. Both species are typical animals consuming gramineous plants: the share of these plants in their diet is 81-83%, the selectivity of graminoids is equal (1.4), the digestibility of food is similar (49-51%). Camels differed from bisons and horses in all the characteristics of their food: forbs (mainly ruderal annual Bassia sedoides (43%) and Atriplex tatarica (20%)) predominated (86%); graminoids amounted to 14%. The selectivity index for forbs was 2.1, including 7.7 and 2.9. for Bassia and Atriplex, respectively. The digestibility coefficient (60%) was much higher in camels than in bisons and horses. Under joint grazing, species with different food selectivity (horse camel or bison camel) evenly affect the plant community of a pasture and preserve its species diversity.