Reproductive ability of cows and their descendants of different generations

Recently, there have been increasing reports in literary sources of the fact that reproductive performance of animals is determined by genetic factors, such as belonging to breed, type, genotype, lineage, parentage, method of selection etc. However, the impact of mothers on indicators of the reproductive capacity of their descendants of different generations has not yet been sufficiently studied. In view of the stated purpose of our research has been to study the reproductive capacity of cows and their descendants of different generations at highly productive herds (average milk yields for cow about 10000 kg). The researches were carried out at herds of LLC "Veleten" of Sumy oblast and PJSC "Plemzavod " Stepnoy" of Zaporizhzhya oblast, created by absorption crossing of the cows of the Ukrainian Black-and-White dairy breed with Holstein breeders. Based on retrospective analysis of zootechnical accounting data (dairy management program herd of Uniform-Agri), and the results of our own researches on cows with calving period between 2004 and 2017: age and live weight at first productive insemination and first calving, duration of calving, period from calving to first insemination (Independence period), service-, dry and inter-calving periods, coefficient of reproductive capacity, calf output per 100 cows, conception rate and reproductive rate were studied. It is established that with each successive generation the age of the first productive insemination of heifers and the first calving of cows decreased, which caused a decrease in live weight of animals in these physiological periods. In both controlled herds, most of the studied features of reproductive ability between cows and their descendants of different generations had a significant difference, each successive generation of animals had better reproductive function than the previous one. In general, the descendants of different generations were noted with good reproduction capability and their ancestors with average, as indicated by this rate. Reproductive rate of descendants, depending on generation and lactation, was in the range of 47,8–52,1, and in the ancestors – in the range 40,2–43,6. Between the reproductive capacity of cows and their daughters, granddaughters and great-granddaughters weak connections of different directions were observed, which were mostly unreliable. Low relative variability of the studied features indicates a low level of inheritance of reproductive qualities of descendants.