Effectiveness of rearing of replacement heifers from Holstein sires

Abstract

A change in the genotype of dairy cattle (when increase in the blood portion of Holstein breed) leads to the fact that it is necessary to develop new requirements for the rearing of replacement young animals. The purpose of the work was to analyze the eff ectiveness of rearing of replacement heifers from different Holstein sires. It was found as a result of the conducted studies that replacement heifers grew approximately the same in terms of growth periods and by the age of 18 months reached a live weight of over 500 kg. Despite this, it is possible to note certain features of the change in live weight in heifers originating from diff erent sires. The characteristics of the growth indicators of heifers from diff erent breeding sires by growth periods indicate that there is a signifi cant diff erence between groups aged 6 months in favor of heifers-daughters of sires Renigade and Maximus (p ≤ 0,01) and 12 months in favor of heifers-daughters of sire Maximus (p ≤ 0,01) compared with herdmates received from the sire Thunderlight. A regular, rhythmic change in the gains of the live weight of young animals by growth periods was noted. A positive correlation was revealed between the live weight at the age of 6 months and the live weight at 10 and 12 months, the average positive correlation between the live weight at 6 months and the live weight at 18 months was obtained. Positive high and average correlation coeffi cients were also established between the live weight at the age of heifers 10–12 months and the live weight at 12 and 18 months. Using the results obtained by analyzing the dynamics of live weight and the growth rate of replacement heifers from diff erent breeding sires and using the correlation coeffi cients between the indicators of live weight for the periods of evaluation of the growth of replacement heifers, it is possible to predict with a high degree of probability the intensity of growth of young animals, starting from the age of 6 months. The rearing of replacement heifers up to the age of the fi rst insemination, regardless of their paternal origin, is effective at a high level of profi tability 55,6–55,8 %. Further rearing of replacement heifers reduces the level of profi tability, this is clearly seen in the rearing of heifers–daughters of sires Thunderlight and Maximus. Taking into account these factors, it is possible to increase the efficiency of rearing replacement young animals on the farm.