Dynamics of live weight and reproductive traits of crossbreds obtained from grading Simmentals with Holsteins

Abstract

The most important condition for increasing milk production is proper rearing of replacement young stock. The purpose of the research was to study the formation of reproductive and productive traits of heifers with high portion of Holstein blood obtained from crossbreeding Simmental cows with sires of Red-and-White Holstein breed during intensive rearing. Analysis of the data obtained made it possible to identify the unequal nature of the dynamics of live weight and growth intensity of experimental animals during their intensive rearing under the conditions of an industrial complex. High-blooded (31/32 Holstein blood) animals respond better to intensive rearing, reaching a live weight of 531,5 kg at 21 months, which was by 17,1–36,6 kg more than their herdmates from other groups. From birth to 21 months heifers with portion 96,87 % of Holstein breed blood were characterized by a large average daily gain, from which they received 782 g, which was 28–57 g more than their herdmates from other groups. A study of the fertility of heifers depending on their weight and age showed that physiological maturity was achieved at a relatively constant live weight at diff erent age periods. The age of fi rst insemination of heifers was in 13–15 months. Upon reaching a live weight of 400–420 kg, 70,0–93,4 % of heifers were effectively inseminated depending on portion of Holstein breed blood. At 12 months of age, heifers with an increased growth rate were inseminated, reaching the live weight of 377–411 kg. Early insemination of heifers did not affect their further growth and development. With the increase in live weight, the fertility of heifers decreased.