Estudo das frequências dos alelos A e B dos genes da Kapa-caseína e beta-lactoglobulina e suas associações com produção de leite em bovinos F1 Girolando

Based on choosing animals with superior phenotypes, artificial selection is traditionally used in animalbreeding programs. The selection of milk cows has been exclusively based on quantitative characteristicssuch as milk production, which is controlled by various pairs of genes making selection a slow process.Production is also subject to the influence of ambient factors. To improve the accuracy of estimates of theanimals breeding value, qualitative characteristics, such as protein types, have been investigated. Theselection of individuals with genes favorable to the desired characteristics, based on their direct DNAevaluation, is called marker assisted selection (MAS). This kind of selection has the advantage that it isable to genotype the animals right after birth and for both sexes. The protein fraction of milk is comprisedby various specific proteins. The most important ones are the caseins and sour protein. Some studies haveassociated the Kappa-casein (k-Cn) and the Beta-lactoglobulin (b-Lg) genes with milk production andquality. The results obtained are mixed, which could be related to genetic differences between and withinbreeds, the number of analyzed samples and the difficulties with statistical analyses. The objective of thisstudy was to associate these markers with milk production and to establish their frequencies. Seventy F1Girolando animals from a milk herd located in the town of Felixlândia in Minas Gerais state weregenotyped, with the objective of associating these markers with milk production and establishing theirgenotypic and genic frequencies. The results showed that 80% of the animals had AA genotype and 20%AB for k-Cn. The gene frequency was of 90% of A and 10% of B. The BB genotype did not appear inthese samples. For b-Lg the genotipic frequencies were 7,14% AA, 57,14% AB and 35,71% BB, and thegene frequencies were 64% for the allele A and 36% for the allele B. There was no trace of associationbetween these two markers and the milk production for this herd