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The experiments were conducted on the broiler chickens of the cross "Smena-9" in the vivarium of the Selective Genetic Centre "Zagorskoe Experimental Breeding Farm" in Sergiev Posad. The results of the blood plasma biochemical tests showed wavelike changes in the trypsin activity at all ages stu- died. The increased concentration of total protein at 7 days of age in all groups could have been induced by switching from endogenous feed when receiving exogenous feed containing more protein than the yolk sac. The age dynamics of the alkaline phosphatase activity had sharp fluctuations throughout the whole rearing period. At 1–7 days of age, there was an increase in the phosphatase activity with a subsequent decrease until 35 days of age relative to the control in all groups. The peak of high activity of this enzyme occurs on the 7th day – 31030 units/l in the control group and on the 14th day in the experimental group 2. Thereafter, there is a gradual decrease in the activity of this enzyme. A sharp increase in the level of alkaline phosphatase in the blood of broiler chickens at 7–21 days of age indicates intensive growth and formation of the organism, but a sharp surge in activity at 7 days of age could also be caused by the transition to a new diet, which in itself is a stress factor. A decrease in the activity of this enzyme at 28–35 days of age indicates a slowdown in the growth process. Consequently, the purpose of this study was to investigate the biochemical composition of blood in different periods of post-embryogenesis of broiler chickens of the cross "Smena-9" at changing the level of protein in the diet, which in this case remains a relevant and informative source of information on the effect of changes in the ingredient composition of feed on the bird organism as a whole.
Kuzmina et al. (Tue,) studied this question.