Influence of genotype and the season of the year on the development of hair coat of heifers

Abstract

The article presents the results of the research on the influence of the season and the genotype of heifers on weight, length, density, structure of the hair coat and the
diameter of its individual structural elements. The object of the study was purebred heifers of the Black Pied breed of the Ural type (group I) and its crossbreeds of the first generation with Holsteins ½ Holstein × ½ Black Pied (group II) and the second generation ¾ Holstein × ¼ Black Pied (group III). The relevance of studying this issue is due to the fact that the hair coat, which has heat protection function, plays an essential role in the adaptation of animals to the
influence of unfavorable environmental conditions. The conducted studies of the development of the heifers` hair coat of different genotypes in “Kolos” LLC of the Orenburg region showed a decrease in the mass, length and density of the hair from 1 cm2 of the skin in summer in comparison to the winter season of the year. The structure of the hair coat also changed. At the same time, the increase in hair mass was 57.9-59.8 mg, length – 7.9-8.9 mm, density – 797-830 pcs. It was found that crossbred heifers of groups II and III were inferior to purebred herdmates of the Black Pied breed of group I in winter according to the hair mass
from 1 cm2 of skin by 3.1 mg (4.15%) and 4.9 mg (6.72%), respectively, length – by 2.1 mm (10.40%) and 3.9 mm (21.20%), density – by 49 pcs (3.37%) and 100 pcs (7.14). Indicator analysis of seasonal dynamics of the hair structure of heifers of experimental groups indicates
that in summer, after coat shedding, the specific weight of under hair decreased, and the guard hair and intermediate hair increased. Thus, in heifers from groups I, II and III, the amount of under hair in the hair sample decreased respectively by 44.9%, 42.8%, 41.1%, and the guard
hair and intermediate hair increased by 35.3% and 9.6%, 33.0% and 9.8%, 31.2% and 9.9%. At the same time, crossbred heifers of groups II and III were inferior to purebred herdmates of Сельскохозяйственный
№2(15), 2022 журнал 84 group I in the specific weight of under hair, respectively, by 3.8% and 5.7%, intermediate hair – by 2.1% and 4.2%, but exceeded them in the content of guard hair by 5.9% and 9.9%. An increase in the diameter of all hair types in summer in comparison to winter period was noted.