Nutrition of bison (Bison bison), camels (Сamelus bactrianus), and horses (Equus caballus) from their joint grazing on an isolated steppe pasture

Resumo

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