Survival rate of dairy heifer calves from birth to one year of age

The study examined the survival rate of dairy heifer calves from birth to one year of age over ten years (2009–2018). The frequency of heifer calves' death in different age periods has been identified, and the frequency of calf death depends on the damage and their milk yield, as well as the season of birth of the heifer calves. In total, 2,825 heifer calves of Ukrainian Black-and-White dairy breeds with a high Holstein share heredity (93 % and higher) were included in the study. The farm where the study was conducted is located in the southern part of the Kyiv region. The average 305-d lactation milk yield was 8463 kg, and the average caw age in the herd – was 1.94 lactations. The calf's housing system was unchanged during the experimental period: colostrum was fed to newborn calves for at least three days, whole milk – until the age of 9–11 weeks; combined fodder intake – as much as calves want during the first month of life and 1.5 kg per day before weaning, getting used to hay from the age of 4 weeks. Calves were housed in individual hutches. It was established that for the investigated period, the herd's survival rate of dairy heifer calves was 85.4 % (81.5...90.1 %); 14.6 % of calves died before the age of one year for different reasons. By age, most heifer calves died within the first month after birth, which amounted to 53.3 % at the age of 1.1–3.0 months – 12.1 %, 3.1–6.0 months – 18.6 %, and 6.1–12.0 months –16.0 %. Dams of died heifer calves were characterized by a slightly older age compared to the average age of cows in the herd (+ 0.21 lactations, P < 0.01) and lower 305-d milk yield in lactation that preceded heifer calf death (-230 kg, P < 0.001). It was found that, depending on the season of birth, the lowest proportion of heifer calves’ deaths was observed in the group born in autumn – 19.6 %; in winter, spring, and summer, the part of heifer calves deaths varied from 26.2 to 27.6 %. Therefore, the survival rate of heifer calves depends to a certain extent on the age of calves, the age and milk productivity of dams, and the season of birth of calves.