Consumption and use of feed ration nutrients by pure-bred and crossbred first-calf cows

The aim of the study is to establish the influence of the genotype of first-calf heifers of the Black-and-White breed, Holsteins of German and Dutch selection and their first-generation crosses ½ Black-and-White × ½ Holstein of German selection and ½ Black-and-White × ½ Holstein of Dutch selection on the consumption and use of nutrients in the feed ration. The studies are conducted in 2019–2020 on animals, adherents of Akas AF LLP, the West Kazakhstan Region. The object of the study is lactating purebred first-calf heifers of the Black-and-White (Group I), Holstein breeds of German (Group II) and Dutch (Group III) selection and their first-generation crosses ½ Black-and-White × ½ Holstein of German selec-tion (Group IV), ½ Black-and-White × ½ Holstein of Dutch selection (Group V). The leading position in the consumption of all types of nutrients was established for first-calf heifers of the Holstein breed of Groups II and III, the minimum number was generally accepted purebred animals of Group I, crosses of Groups IV and V occupied an intermediate position. First-calf heifers of groups II–V exceeded their peers of group I in the consumption of all types of nutrients by 12.5–1105 g (2.22–6.68 %). At the same time, crossbreeds of groups IV and V were inferior to purebred first-calf heifers in the consumption of nutrients by 6.9–737 g (1.18–4.36 %). An advantage of first-calf heifers of groups II–V over their peers of group I was noted in the amount of digested nutrients within 11.9–1014.0 g (3.11–7.78 %). In turn, crossbreeds of groups IV and V were inferior to purebred first-calf heifers of groups II and III in the analyzed indicator by 14.0–548.0 g (3.52–4.79 %). When analyzing intergroup differences in the nutrient digestibility coefficient, its minimum value was found in purebred first-calf heifers of group I, which were inferior to their peers of groups II–V by 0.06–3.92 %. At the same time, crossbreeds of groups IV and V were inferior to purebred first-calf heifers of groups II and III in terms of the nutrient digestibility coefficient by 0.85–1.68 %. The leading position in terms of the digestibility coefficient of all types of nutrients was occupied by first-calf heifers of group III, while their peers of group II were inferior to them by 0.76–1.10 %. The manifestation of the crossbreeding effect in both the consumption of nutrients and their use differed in the crossbreeding of groups IV and V.