[Carotene content in the vegetation of sandy saxaul-Ilak-Selinum associations in the South-Western Kyzyl Kum [Availability of vitamin A on pastures for Karakul sheep]]

besoin nutritionnel breeds carotenoide carotenoides carotenoids desert deserts desiertos feed grasses grazing necesidades de nutrientes nutritional requirements ovin ovinos pastoreo race razas retinol sheep