The influence of Holstein crossbreeding on the reproductive qualities of Black-and-White cows

The purpose of the research was to study the main indicators of the reproductive ability of Black-and-White cows, depending on the proportion of Holstein genes. As the material for the research there were taken the data of breeding and zootechnical records of cows of Black-and-White breed of CJSC Semenovsky Breeding Plant of the Mari El Republic. The results of the research showed that with an increase in the proportion of thorough-bredness on the Holstein breed the reproductive ability of cows improved. Thus, the first-calf heifers with a low proportion of Holstein genes (up to 12.5 %) had the latest age of the first fruitful insemination and the first calving (21.9 months and 32.3 months). With an increase in thorough-bredness up to 87.6 % and more, the age for the first insemination decreased by 7.7 months (31.8 %), the age of the first calving - by 7.4 month (21.8 %), fertility index increased by 5.8 (14.6 %). At the same time, the duration of the service period in high-blooded animals increased by 18.8-26.4 days (15.8-23.8 %). The duration of the calving interval in all genetic groups exceeded the optimal time and changed in accordance with the change in the service period. The longest calving interval was in cows with the thorough-bredness degree of 87.6 % (13.8 months), which was 0.1-0.7 months longer than in animals of other genetic groups. There was a low coefficient of reproductive ability of the studied animals of all genetic groups ‒ 0.91-0.93. The significant influence of Holstein genes on the age for the first fruitful insemination (ɳ2 = 9.57 %), the first calving (ɳ2 = 8.80 %) and the fertility of cows (ɳ2 = 1.98 %) (P≤0.05) was established. The effect of the genotype on the duration of the service period and calving interval was weak (ɳ2 = 0.09 % and ɳ2 = 0.26 %) and unreliable.