The article shows the results of studying the consumption and use of essential nutrients and energy from the fodder in the diet of the purebred heifers and the heifers obtained by crossing the Kazakh white-headed and Hereford breeds. The objects of the study were the heifers of the following genotypes: I — Kazakh white-headed, II — ½ Hereford x ½ Kazakh white-headed, and III — ¾ Kazakh white-headed x ¼ Hereford. It has been found that the crossbred young animals featured greater consumption of all types of fodders in the diet than the purebred animals. Typically, the leading place in the consumption of all types of fodder is occupied by the half-breed heifers in group II (½ Hereford x ½ Kazakh white-headed). The experimental materials obtained during the physiological (balance) experiment are evidence of the effect of the genotype of the heifers on the consumption and digestion of certain types of nutrients in the diet. It should be noted that the purebred heifers were inferior to the crossbreeds in groups II and III in the consumption of dry matter, respectively, by 126.90 g (2.0 %) and 52.9 g (0.8 %), organic matter — by 139.24 g (2.4 %) and 71.35 g (1.2 %), crude protein — by 42.35 g (4.3 %) and 31.1 g (3.1 %), crude fat — by 4.59 g (2.1 %) and 1.92 g (0.9 %), crude fiber — by 36.41 g (2.4 %) and 15.14 g (1.0 %), and nitrogen-free extractive substances (NFES) — by 55.89 g (1.8 %) and 22.86 g (0.7 %). The purebred heifers of the Kazakh white-headed breed were inferior to their crossbred analogs in groups II and III by the amount of digested dry matter, respectively, by 150.62 g (3.6 %) and 68.97 g (1.6 %), organic matter — by 146.41 g (3.7 %) and 69.35 g (1.7 %), crude protein — by 35.24 g (5.6 %) and 27.00 g (4.3 %), crude fat — by 35.24 g (5.6 %) and 2.15 g (1.4 %), crude fiber — by 28.53 g (3.2 %) and 13.07 g (1.5%), and NFES — by 77.59 g (3.3 %) and 27.13 g (1.2 %). The leading position of the heifers in experimental group II (1/2 Hereford x 1/2 Kazakh white-headed) by the value of the analyzed parameter was established. Due to the greater amount of nutrients consumed and digested from the diet, the crossbred heifers in groups II and III were superior to the purebred Kazakh white-headed heifers in terms of the digestibility coefficient. A similar situation was observed in the use of energy. For instance, the heifers in groups II and III were superior to their peers in group I by the consumption of gross energy, respectively, by 2.90 MJ (2.5 %) and 1.53 MJ (1.3 %). A similar pattern was also observed for other types of consumed energy. During the experiments, it was found that the Kazakh white-headed heifers in group I were inferior to their crossbred peers in groups II and III in nitrogen consumption by 6.78 g (4.3 %) and 5.03 g (3.2 %). Typically, almost equal amounts of nitrogen were excreted in the feces of the heifers of various genotypes: 57.76 — 58.78 g. At the same time, the crossbred heifers in groups II and III showed better digestibility of proteins nitrogen from the feed diet.
