Productive qualities of daughters of bulls-producers evaluated by the "Life of Calves" (HLIV)

Abstract

In the evaluation of Holstein bulls, the "Heifer Life Expectancy" (HLIV) trait is a health indicator. Selecting for this trait can reduce animal mortality and lower herd replacement costs. The predicted HLIV transmission capacity is positively correlated with milk production, as well as with the traits "Productive Life Expectancy," "Easy Calving," and "Approaching First Calving." However, the level of genetic potential realization for these traits varies significantly among the daughters of different bulls. The purpose of the research is to conduct a comparative assessment of the preservation, growth, and development, as well as the milk production and the implementation of the predicted HLIV transmission capacity in the offspring of Holstein bulls with equal HLIV values, which are kept under the same conditions of housing, feeding, and operation. The research was conducted at a breeding farm in the Stavropol Territory on Holstein animals from birth to the end of their first lactation. According to the primary zootechnical and veterinary reports, the live weight, survival rate of the experimental animals from birth to 18 months, milk yield, and percentage of fat and protein in milk during the first 305 days of lactation were studied. It was found that, despite the similar evaluation of the bulls based on HLIV, their offspring had significant differences in the studied parameters. It was found that, with the same evaluation of bulls-producers by the HLIV trait, their offspring had significant differences in the studied indicators. The heifers of the I experimental group exceeded the heifers of the II experimental group in live weight at all periods of cultivation. The greatest difference in this indicator was at the age of 18 months – 39.0 kg. The survival rate in the first experimental group was 94.7%, compared to 88.5% in the second experimental group, with milk yields of 7869.9 and 6683.0 kg, respectively.