The purpose of the research is to study the effect of coccidiosis infection (cryptosporidiosis, eimeriosis) on the average daily gains in live weight of young cattle.Materials and methods. The studies were carried out on animals spontaneously infected with Eimeria spp. And Cryptosporidium spp. According to the principle of analogues, 4 groups of animals were formed, 10 heads each. In the first experiment, the average daily weight gain of 1-20-day-old animals infected with Cryptosporidium (1st experimental group) and clinically healthy calves (1st control group) was compared. For the second experiment, calves at the age of 2-4 months, infected with Eimeria spp. (2nd), were selected, young animals free from infection were selected in the second control group.Results and discussion. In calves infected with Cryptosporidium spp., the average daily gains ranged from 0.597±0.017 to 0.675±0.018 kg. The decrease in growth per day relative to the animals of the control group was, on average, 0.346 kg. The maximum loss of weight gain, 11.0±0.88 kg, was recorded in November. A similar dynamic of the decrease in average daily weight gain was established in animals at eimeriosis. During the research period, the shortfall in live weight of calves infected with Eimeria spp. was 21.5±2.6 kg, which is 12.3 kg less relative to the mass of calves infected with Cryptosporidium spp. Sharp fluctuations in the reduction of average daily weight gain in this group were not recorded: on average, 0.248±0.113 kg relative to the control group. Thus, the reason for the lack of live weight gain (up to 40 %) in calves in the farm of the Uvinsky district of the Udmurt Republic is intestinal coccidiosis. The minimum indicator of the average daily gain in live weight (0.597±0.017 kg) falls on the group of calves infected with cryptosporidiosis, which is almost 2 times less relative to the gain of animals from the control group.