Cow reproduction rates with varying inbreeding degrees

The evaluation of the breeding work results carried out, the identification of optimal systems for the animal’s selection, including related ones, have always been relevant. The purpose was to study the influence of various inbreeding degrees on reproductive abilities and their selection and genetic parameters in Holstein cows. The research was carried out on the basis of ‘Pushkinskoe’ Breeding Plant, Nizhny Novgorod region. At the earliest age, heifers were inseminated in the group with recent inbreeding (14.87 months), for this reason they had the lowest weight at the first insemination - 4 25.7 kg. Cows in the group with recent inbreeding had the shortest service period (108.9 days), the longest service period was in the group with close inbreeding (152.6 days). The variability of live weight during the first insemination and fertilization in all groups was at a low level (C_v = 5,22…8,25 %). The duration of the service period after first lactation in all groups, except for the group of close inbreeding, had a variation of about 45 %, in the group with close inbreeding it was 1.5 times higher. Despite its small number, the group of close inbreeding turned out to be the most variable in all indicators. An increase in the age of the first fertilization of heifers in the group of close inbreeding leads to an increase in the duration of the service period (r = 0.335). However, there is practically no connection between these indicators in the other groups. Many of the studied indicators had a weak positive or negative relationship with each other. Among the resulting young, more than half were heifers, in groups with different inbreeding degrees this indicator varied from 63.3 to 66.7 %, in the group with outbred animals it was 69.4 %. Twins were registered 2 times and only in the group with a recent inbreeding degree. Stillbirth in all groups was at a fairly low level - 5 .7…6.7 %, in the group with a close inbreeding degree no cases of stillborn calves were detected. The birth of calves with congenital deformities and pathologies from related mating was not observed. Thus, in the conducted studies, inbreeding had no negative impact on the cow’s reproductive qualities even to a close degree.