Influence of Paratypic Factors on the Fertility of Dairy Cows and Replacement Heifers

Abstract

The results of researching the influence of the season, air temperature, age, stage of lactation, insemination number and daily milk yield on the fertilization of heifers and cows under different housing technologies are presented. It was established that the best fertilization was demonstrated by heifers kept in tethered housing at PE Agroprogres. Nevertheless, the fertilization rate of cows among the farms under study was the highest under free housing (p<0.001). By months of the year, in general, on all farms, a trend of a greater number of inseminations of heifers was observed in spring and summer, although no clear dependence was established. The share of fertile inseminations of heifers of PE Agroprogress varied from 56% in October to 92% in June. Fertilization of heifers at SE EFs named after Dekabrists and Kutuzivka had less variability: from 47% in February to 70% in May in the first farm and from 46% in May to 60% in July in the second farm, respectively. At PE Agroprogres and SE EF named after Dekabrists, there was a tendency to increase the fertilization of heifers at the air temperature above 20 ºС. Cows of PE Agroprogres and SE EF named after Dekabrists had the lowest fertilization rate at temperatures below -10 ºC. There was also a trend of its increase with an increase in air temperature above 20 ºC. It was established that at PE Agroprogres (tethered housing) a clear trend of increasing the fertility of cows was observed during the period of summer open air housing, at SE RF named after Dekabrists this trend is almost imperceptible, and the opposite dependence has been established at SE EF Kutuzivka (year-round free housing keeping with feeding on walking platforms). At all studied farms, there was a clear tendency in decrease of the fertilization of cows during the period of high milk productivity. Cows of PE Agroprogres and SE EF Kutuzivka with a daily milk yield of more than 40 kg of milk were fertilized worse by 1-4% (р<0.1) and 5-6% (р<0.001) than animals with a lower milk yield. Cows of the SE EF named after Dekabrists with a daily milk yield of more than 30 kg also had 8-9% (p<0.001) worse fertilization compared to animals with lower productivity. At all studied farms, the highest percentage of fertilization was characterized by heifers at their first insemination, and among cows were animals of the first and second calving. According to all inseminations, the average day of lactation of cows with their artificial insemination was 38-54 days longer at SE EF named after Dekabrists in comparison with PE Agroprogres and SE EF Kutuzivka (p<0.001). The share of fertilized cows during the breeding period up to 90 days after calving was lower by 6% At PE Agroprogres, and by 9% at SE EF named after Dekabrists, and by 6% at SE EF Kutuzivka than in the mid-lactation period (91-180 days) (р<0.001).