The experiment was carried out in the Tribal reproducer «Kolhoz Tomichevsky» in Belogorsk district of the Amur region. The object of the study was the Hereford calf bulls. For the experiment, a group of 10 bull heads at the age of 6 months was formed. In the warm season, the animals were kept on natural pastures, in the cold season – in pens on the farm. At the age of 18 and 24 months, 3 bulls from the group were weighed and slaughtered for histological examination of the muscle tissue of the thigh muscles. It was found that, muscle tissue of 18-month-old calf bulls was in the process of active growth and differentiation, had a dense arrangement of muscle fibers in bundles of primary and secondary orders in the absence of pronounced development of adipose tissue in the connective tissue layers. By the age of 24 months, the number of muscle fibers in an area of 0,8 mm2 of the cross section of the thigh muscle tissue decreased: in the biceps and semitendinosus muscles – by 16,7–18,8 %, in the semimembranous, adductor and gracilis muscles by 1,6–1,9 times. A decrease in the number of muscle fibers in the semimembranosus, semitendinosus and adductor muscles of the thigh was observed due to an increase in the diameter of muscle fibers by 7,2–31,5 %, while reducing the perimysium thickness by 1,8–4,0 % times, which indicated the increase and development of these muscles in the thickness and high tenderness of the meat. On the contrary, in the biceps thigh muscle of 24-month-old Herefords, there was no increase in muscle fiber diameter, and an increase in thickness of endomysium by 34,9 % and a perimysium by 19,8 % contributed to an increase in the rigidity of meat containing this muscle. In the gracilis muscle of the thigh, the cross-sectional area of muscle fibers decreased by 17,0 %, the thickness of the endomysium – by 13,1 % and the thickness of perimysium – by 42,9 %, in the absence of the development of adipose tissue in these layers, which also indicated a decrease in the nutritional value of meat containing this muscle in Herefords at the end of the winter-stall detention period.

Mansurova Mariya S., Ostyakova Marina E.

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