FORMATION OF ECONOMICALLY USEFUL TRAITS IN COWS OF UKRAINIAN BROWN DAIRY BREED OF DIFFERENT GENOTYPES BY KAPPA-CASEIN

Abstract

The genes of cattle casein are polymorphic. Today, a large number of variants of kappa-casein protein are known: A, B, B2, C, D, E, F1, F2, G1, G2, H, I і J. Scientists pay attention to three main types of genotypes – AA, AB and BB. It has been proven that the most common alleles of kappa-casein in cattle are A and B. Importantly, the allelic variant of kappa-casein B is associated with the production of milk with a more optimal chemical composition and technological parameters for cheese production compared to the A allele. According to the results of scientific research, it was established that the level of milk yield in cows with the AA genotype was higher compared to animals of other genotypes. At the same time, animals with the BB genotype are characterized by a higher protein content in milk compared to milk from animals with the AA genotype. Scientists have also proven that the milk of animals with the desired genotype (BB) curdles faster during cheese production, and the yield of cheese is higher than that of animals with the AA genotype. In confirmation of this, other researchers note that animals with the AA genotype have a lower average protein content in milk (by 0.09%) compared to animals with the BB genotype. The purpose of the study is to establish the influence of kappa-casein genotypes on economic and useful traits of animals of Ukrainian Brown Dairy breed. Research materials and methods. Genotyping of 42 heads of Ukrainian Brown Dairy breed cattle belonging to the Breeding Plant of the State Enterprise "Experimental Farm of Institute of Agriculture of Northern East of NAAS" was carried out. Determination of kappa-casein gene polymorphism was carried out in the genetic laboratory of the Institute of Physiology named after Bogomolets of NAS with the help of molecular biological analysis of allele recognition by polymerase chain reaction (PCR) in real time. Blood samples were collected in monovets with a volume of 2.7 ml (Sarstedt, Germany), with subsequent freezing of the samples and their storage at -20ºC. DNA for genotyping was obtained from samples using the Monarch® New England BioLab (USA) genomic DNA purification kit according to the manufacturer's protocol. Three sub-experimental groups of Ukrainian Brown Dairy breed animals with genotypes according to kappa-casein AA, AB and BB were formed. The electronic database of SUMS "Orsek" was used to evaluate economic and useful features. Changes in live weight of cattle up to 18 months of age, indicators of reproductive capacity, and milk productivity were evaluated. The research results were processed using the methods of mathematical statistics using the "Statistica-6.1" package in the Windows environment on a personal computer. As a result of the conducted research, no significant influence of the kappa-casein genotype on live weight indicators of heifers was established in all studied periods. This indicates that when creating herds of animals with the desired BB genotype, the growth indicators of repair heifers will not deteriorate. According to indicators of reproductive capacity, there is no statistically significant difference between animals of different genotypes. At the same time, the youngest age of first insemination was distinguished by animals with the AB genotype, and the highest – with the AA genotype. The duration of the intercalving period and the value of the coefficient of reproductive capacity were the lowest in homozygous (AA) and heterozygous (AB) animals. During the first lactation, homozygous AA animals had an advantage in the content of fat and protein in milk. Homozygous BB cows had an advantage in terms of milk yield in the third lactation, in terms of fat content – animals with heterozygous genotype AB, protein – animals with genotype AA. In terms of better lactation, animals with the BB genotype prevailed over other groups in terms of milk yield. Homozygous AA animals had an advantage in terms of fat content, and homozygous BB animals had an advantage in terms of protein content. Conclusions. Animals of the Ukrainian Brown Dairy breed corresponded to the standard of the breed in almost all indicators of milk productivity. Between animals of different genotypes, according to kappa-casein, a difference was established for certain economic and useful traits. It should be noted that in different periods and according to different characteristics, it varied greatly, and in some cases it was statistically significant. In the third and best lactation according to milk yield, a statistically significant difference was established between homozygous BB, heterozygous AB genotypes and homozygous AA in favor of the first two genotypes. It can be stated that the formation of herds with the BB genotype for kappa-casein will ensure the preservation of the desired values of productive indicators of dairy cattle.