Age variability of the live weight of heifers depending on the part of blood of Holstein breed

Abstract

Much attention when breeding dairy cattle is paid to the genetic potential of the livestock and the improvement of methods of its use. This is due to the fact that at present the number of crossbred animals with different parts of blood of Holstein breed has significantly increased, but there are no proven methods for determining the optimal part of Holstein blood, as a result of which the question of the association between the productivity of animals and their genotype remains very relevant. The research has been carried out under the conditions of JSC “ART” in the Right-bank district in the Republic of North Ossetia-Alania. For the purpose of conducting a scientific experiment, 3 groups of heifers of the line Reflection Sovereign 198998 have been formed with 10 heads in each. At the same time, the proportion of blood of the black-and-white Holstein breed in the experimental heifers was in the range from 50 to 75 %: 1st group – 1/2-blooded, 2nd group – 5/8-blooded and group 3rd – 3/4-blooded. The groups have been formed at the birth of young animals according to the method of analogues, taking into account the live weight and productivity of their ancestors. Accounting for the growth and development of heifers has been carried out by weighing at birth, at 3 and 6 months of age. The calculations made it possible to trace the dynamics of the variability of the live weight of experimental animals. The results obtained indicate the association between the indicators of live weight of heifers and their genotype. Against the background of the same conditions of maintenance and feeding in all age periods, the heifers of the 2nd group were superior in terms of live weight to the herdmates of the 1st and 3rd groups. So, with approximately the same live weight at birth with the herdmates of other groups, the heifers of the 2nd group at 3 months of age exceeded the half-blooded heifers from the 1st group by 3,2 kg or by 3,67 %, the 3rd group by 2,0 kg or by 2,26 %, at 6 months of age by 4,9 kg or by 3,27 % and by 3,3 kg or by 2,18, respectively. Heifers of the 3rd group slightly outstripped in the live weight of their herdmates from the 1st group. The fact that the heifers of the 2nd group (5/8-blooded according to Holstein) had better indicators of live weight compared to their herdmates of the 1st and 3rd groups (1/2-and 3/4-blooded), is proof of the influence of their genotype on the intensity of live weight gain.