The effect of homogeneous selection on the reproductive qualities of cows of the Sychev breed

A large amount of data has been accumulated indicating a decrease in the effectiveness of breeding work with dairy cattle due to significant problems with reproduction. In breeding, not only the breeding method is of particular importance, but also the method of selection, on which their reproductive ability depends. The article considers the issue of the influence of the degree of inbreeding, as an extreme form of homogeneous selection, when using the method of linear breeding of cows on their reproductive qualities. The research was carried out on the livestock of 437 cows of the breed of Sychevka, which calved for the first time in the period 2013-2022 in Vostok LLC of the Smolensk region. For a retrospective analysis, the number of cows was taken, the proportion of blood in the improving Holstein breed of which does not exceed 25 %. The values of the age of the first calving, the indifference period and the service period obtained as a result of the research do not significantly depend on the degree of inbreeding applied; however, they have different indicators in the context of linear affiliation. The largest number of livestock with a high degree of inbreeding was found in the Klever 68 line (52.5 %). The breeding stock of the Aromat 3433 lines and Danzig 3641 are completely out breed. Only in the Toreador 3032 line, the livestock obtained using closely related selection has a significantly low age of the first calving (29.7 months). Throughout the studied livestock, the most precocious animals are out breeding selection. One of the lowest age of the first calving in cows from the line Anis 4593, obtained without the use of inbreeding (28.1 months). The average values of the herd's indifference period in Vostok LLC indicate that the sexual cycle of 58 % of cows resumes within 60 days after calving. The service period of animals in Vostok LLC is closest to the optimal values for cows from the Anis 4593 and Danzig 3641 lines (46–95 days) with remote inbreeding and out breeding selection. In the descendants of the Klever 68 line, with closely related selection, the longest service period exceeding 165 days was revealed in the first lactation. The share of the influence of the degree of inbreeding on the age of the first calving and the indifferent period of cows of the Sychevka breed in an agricultural enterprise does not exceed 5 %.

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