ANALYSIS OF COMPLEX GENOTYPES OF BETA- AND KAPPA CASEIN OF BULLS OF DAIRY BREEDS
Authors: Ladyka V. I. , Sklyarenko Y. I. , Pavlenko Y. M. 
Published: November 2020

Marker-dependent breeding is one of the most relevant areas for improving the dairy productivity of cattle. It allows the selection of parent forms at the gene level. The growing demands of the market for milk quality make it necessary to select dairy herds using genetic markers associated with qualitative characteristics of milk productivity. A topical issue in dairy cattle breeding today is the study of the relationship between hereditary factors that determine the types of proteins in milk. Casein is the main component of milk proteins and is represented by three fractions – alpha (CSN1S1), beta (CSN2) and kappa (CSN3). The content of individual casein fractions depends on the breed of cows. Genetic variants of beta-casein significantly affect human health, while kappa-casein is associated with the quality of milk and the greater suitability of milk for processing and cheese production. The aim of this work is to evaluate the genotype of sires approved for use in Ukrainian farms in 2020 based on beta- and kappa-casein genes. Materials and methods. The research was conducted by analyzing the catalog of bulls of dairy and dairy-meat breeds for breeding stock reproduction in 2020. Bulls were analyzed according to the genotype of beta – and kappa-casein of Holstein (n = 872), Simmental (n = 17), Montbellard (n = 3), (wro.synel.net; motbeliarde.org) Jersey (n = 59), Red Danish (n = 8), Red Norwegian (n = 7), Schwyz (n = 17), Aishir (n = 8) breeds, evaluated by offspring quality and genomic assessment. The website DairyBulls.com is used to analyze the results of the evaluation of bulls-producers on a set of characteristics. The research results were processed by mathematical statistics methods using the "Statistica-6.1" package in a Windows PC environment. It was found that the majority of bulls-producers approved for use were evaluated based on these genotypes. Depending on the breed, the number of bulls estimated by the studied characteristics ranged from 43 to 85%. Depending on the breed, from 2 to 16 different combinations of beta- and kappa-casein genotypes were identified. The frequency of occurrence of the desired complex genotype A2A2/BB, depending on the breed, was in the range of 0.0 to 75.0%. Holstein bulls of the desired A2A2/BB genotype were estimated to be superior to bulls of some other complex genotypes in terms of daughter milk yield, the amount of milk fat, milk protein, lifetime profit indices, cheese profit, and milk profit. Therefore, the use of sperm production of bulls with the A2A2/BB genotype will improve the economically useful characteristics of offspring, and will further increase the number of livestock with the desired complex genotype. Summary. 1. Taking into account the data of many domestic and foreign scientists who claim that the genotype of animals by the beta – and kappa-casein polymorphism affects the qualitative composition of milk, it is necessary to have in herds the necessary number of animals carrying the A2 allele of beta-casein and the B allele of the kappa-casein gene. The desired breeding parameters of the herd can be achieved by using bulls with BB genotypes for kappa-casein and A2A2 for beta-casein. Correction of the bulls-producers selection system can only be carried out if the breeding stock of the herd is genotyped according to the polymorphism of the beta-and kappa – casein genotypes. Holding this event will increase the protein content and will improve cheese suitability of milk of cattle of future generations. The use of bulls-producers without taking into account their genotypes for the casein fractions described above and the lack of polymorphism control of these genes among cows can lead to a decrease in the frequency of desired genotypes in the herd and a decrease in the technological qualities of milk as raw materials. 2. The created database of bulls-producers approved for use in Ukraine, evaluated by the beta-and kappa – casein genotypes, allows us to establish a positive perspective on the possibility of forming staffed herds of animals with the desired complex A2A2/BB genotype in Ukraine. 3. It was found that bulls of dairy breeds have different frequencies of beta – and kappa casein alleles. The part of bulls-producers of the desired complex genotype A2A2/BB of Holstein breed is 8.49%, Holstein Red-pockmarked – 2.94%, Schwyz – 75%, Jersey – 13.79%, Red Danish – 12.5%, Red Norwegian – 20.0%, Montbellard – 25%. Among animals of Simmental and Aishir breeds – bulls with the desired complex genotype A2A2/BB were not detected. 4. Bulls of the desired complex genotype A2A2/BB according to the indicators of milk yield of daughters, the amount of milk fat, milk protein, indices of lifetime profit, profit for cheese, profit for milk were dominated bulls with separate complex genotypes CSN2-CSN3