INDICATORS OF THE DEVELOPMENT OF THE HAIR COVER OF HEIFERS OF DIFFERENT GENOTYPES BY SEASONS OF THE YEAR

Abstract

The article presents the results of studying the influence of the season of the year and the genotype of heifers on the weight, length, density, structure of the hair cover and the diameter of its individual structural elements. The object of the study were purebred heifers of the black-mottled breed of the Ural type (group I) and its crossbreeds of the first generation with holsteins ½ holstein × ½ black-mottled (group II) and the second generation ¾ holstein × ¼ black-mottled (group III). The relevance of studying this issue is due to the fact that the hair covering, performing a heat-protective function, plays an essential role in the adaptation of animals to the effects of adverse environmental conditions. The conducted studies of the development of the hair cover of heifers of different genotypes in LLC "Kolos" of the Orenburg region found a decrease in the mass, length and density of the hair from 1 cm2 of the skin in the summer compared with the winter season of the year. The structure of the hairline 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 peers of the black-and–white breed of group I in winter by 3.1 mg (4.15%) and 4.9 mg (6.72%), respectively, by 3.1 mm (10.40%) and 3.9 mm (21.20%) in hair weight from 1 cm2 of skin, respectively., density – by 49 pcs (3.37%) and 100 pcs (7.14). Analysis of indicators of seasonal dynamics of the structure of the hair of heifers of experimental groups indicates that in the summer season of the year after the spring molt, the specific weight of down decreased, and the awn and transitional hair increased. Thus, in heifers of groups I, II and III, the fluff content in the hair sample decreased respectively by 44.9%, 42.8%, 41.1%, and the remaining and transitional 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 peers of group I in the specific weight of down, respectively, by 3.8% and 5.7%, transitional – by 2.1% and 4.2%, but exceeded them in the content of awn by 5.9% and 9.9%. An increase in the diameter of all hair types in the summer compared to the winter period was found.