The successful development of horse breeding requires the search for new technological solutions, the use of which will improve the quality and reduce the cost of compound feed. At the same time, it is important to breed and maintain horses with high adaptive capacity, capable of withstanding the action of negative environmental factors without reducing their performance. Sport horses require special treatment and an individual approach in the selection of diet and breeding conditions. We investigated the effect of granulated feed containing alfalfa and mineral-vitamin complex. Haemoglobin level in the studied animals amounted to 152.6 g/L, 8.1% higher than in control peers. The 15.1% higher content of erythrocytes in blood in horses of the experimental group may indicate more intensive blood saturation. The analysis of variance revealed a significant and highly probable influence of feed on haemoglobin content, number of erythrocytes and leukocytes in the horses' blood, the share of influence for which was the greatest and ranged from 56.4 to 66.0%. It was found that the greatest positive correlation was observed between the amount of consumed dried alfalfa and the level of haemoglobin, colour index, number of erythrocytes and leukocytes in the blood of young horses (r=0.32 ± 0.10; 0.26 ± 0; r=0.43 ± 0.25; r=0.41 ± 0.09, respectively). It was also found that horses in the experimental group were more heat tolerant compared to the control group horses indicating their greater adaptability. The experimental horses' body temperature measured immediately after their walk was 38.2 °C, which was 0.8% lower than in the control group. One hour after the walk, their body temperature was almost the same as at rest (37.9 °C). In horses of the control group during the same period, the body temperature was 38.0 °C, which is 0.4 °C higher than their temperature at rest before the walk. The use in the diets of the studied animals of full-fed pelleted forages allowed raising animals of strong physiques, having more intensive metabolism and more pronounced adaptive and compensatory abilities in comparison with their peers of the control group.