In the course of growing heifers on tethered content, there is a tendency to some decrease in the severity of platelet lipid peroxidation due to an increase in their antioxidant protection. In platelets, this is accompanied by activation of the actin-myosin system, a high level of adenosine phosphates, and their intense secretion in the case of platelet participation in hemostasis. The observed heifers showed a tendency to increase the hemostatic functions of platelets, manifested in the blood and in vitro. The revealed slight increase in platelet activity in tethered heifers is caused by maturation during rearing of surface and intracellular mechanisms of platelet participation in hemostasis and microcirculation processes.