Productivity of cows depending on the type of mating and genotype of sires

Abstract

At breeding enterprises, the number of sires of Holstein breed homozygous for the genotype of the ЕАВ-locus is increasing, and there is a tendency for inbreeding coefficients to increase in populations of this breed. The dairy productivity of fi rst-calf heifers obtained from heterozygous and homozygous sires, as well as the change in indicators per generation with intra-line mating and line crosses were studied. It was found that in terms of the total yield of milk fat and protein for 305 days of lactation in the line Wes Back Ideal 1013415, the fi rst-calf heifers obtained from intra-line mating and line crossing exceeded the cows their mothers by 21,4 kg, and in the whole group of fi rst-calf heifers of homozygous sires this indicator was 51,0 kg higher against the average of fi rst-calf heifers of heterozygous sires. At the same time, for the cow-mothers of these groups, the corresponding diff erence was negative: –31,6 and –64,7 kg. Similar data were revealed for another main line Refl ection Sovereign 198998. When mating heterozygous sires according to the variants of line crosses, the milk yield was 227 kg higher (p < 0,05), but the mass fat fraction in milk decreased by 0,06 – 0,08 abs.% (p < 0,01). However, the levels of manifestation of traits among fi rst-calf heifers in comparison with cow-mothers with intra-line mating increased by groups of homozygous sires in milk yield by 32,5 %, mass fat fraction by 17,6 % and mass protein fraction by 25,0 %. The correlation coefficients «mother – daughter» for milk yield, mass fat fraction and mass protein fraction were relatively higher in the group of homozygous sires, whose heritability coeffi cient in one of the farms for milk yield was higher by 0,495, mass fat fraction by 0,305; mass protein fraction by –0,110, and in the other, respectively, by 0,026; 0,161; 0,121. The conclusion is made about a higher prepotency of heterozygous sires with improving mating.