INFLUENCE OF THE GENOTYPE OF BEEF BULLS ON THE DEVELOPMENT OF HAIRLINE
The article presents the results of the assessment of the development of the hair cover of calves of Kalmyk (group I), Aberdeen-Angus (group II) and Hereford (group III) breeds in the winter and summer seasons. It was found that in the summer season, compared with the winter period, bulls of all genotypes had a decrease in hair mass from 1 cm2 of skin by 59.6-66.7 mg, its length by 22.4-25.4 mm and density by 634-996 pcs. At the same time, bulls of the Kalmyk breed of group I surpassed peers of the Aberdeen-Angus and Hereford breeds of groups II and III in the winter season by hair weight from 1 cm2 of skin, respectively, by 12.2 mg (15.97%) and 10.6 mg (13.59%), its length - by 7.4 mm (21.39%) and 4.0 mm (10.53%), density - by 554 pcs (38.58%) and 312 pcs (18.59%). Similar intergroup differences were observed in the summer period. When analyzing the seasonal dynamics of the ratio of individual hair types, an increase in the specific weight of the guard and transitional hair in the summer season of the year was found with a decrease in the proportion of fluff in the sample in bulls of all experimental groups. At the same time, in the winter season, the gobies of the Aberdeen-Angus and Hereford breeds of groups II and III were inferior to the young of the Kalmyk breed of group I in terms of the specific weight of down in the hair sample, respectively, by 5.5% and 2.6%, transitional - by 3.9% and 2.4%, but exceeded them in the content of the backbone fibers - by 9.4% and 5.0 %. There were no significant intergroup differences in the diameter of the down, transitional and guard hairs. At the same time, an increase in the diameter of all hair types was observed in bulls of all genotypes.