Polimorfismos do gene BoLA-DRB3 em rebanhos bovinos leiteiros 5/8 girolando e holandês no estado de Pernambuco

Abstract

Selection in dairy cattle was turned over time, increasing the quantity of milk, while features related to the milk constituents and disease resistance have been hardly considered in breeding programs. This intense selection to production characteristics led to an increased incidence of diseases such as mastitis, which is one of the factors that cause economic losses in milk production chain. Therefore, it has been given great attention in the identification of genes or chromosomal regions and their associated with resistance to this disease, in order to select animals productive and resistant at the same time. A region of the genome associated with bovine mastitis is the Major Histocompatibility Complex (MHC), that the bovine region was named BoLA. However, currently there are no studies related to the identification of gene polymorphisms in BoLA-DRB3 herds in the state of Pernambuco. With this objective, we analyzed herds 5/8 Holstein-Gir and Holstein the state of Pernambuco, to evaluate gene polymorphisms BoLA-DRB3.2, by using a modified protocol of the method of polymerase chain reaction (PCR), allowing identification of alleles. The modification of the protocol was adequate and satisfactory to indication of gene polymorphisms studied. We identified 39 alleles, where three sequences (AV-141f, AV and AV-18F-133F) were considered more likely. The allele frequencies ranging between 0.42 and 15.97%, where the most common alleles were 0101 (6.13%), R (14.11%) and 1101 (14.72%). There were low of similarity values, demonstrating greater genetic variability among animals. The distance estimated between the Holstein-Gir and Holstein, was 0.075 and the average distance among the flocks of 0.002. The observed heterozygosity (Ho) had values lower than expected heterozygosity (He), indicating that there are fewer heterozygotes in the population than expected by the Hardy-Weinberg equilibrium. The genetic divergence between the sequences of the general population was 40.8792, the greater the divergence found in a population greater the number of different alleles. Phylogenetic analysis checks the formation of six groups found between all alleles of the tree with the cutting around 0.04 similarity. Thus, there was a high polymorphism BoLA-DRB3.2 for the animals studied, reported as the alleles found to confer resistance to mastitis. The animals of the study show high variability characterized with a high genetic value for livestock, such information to be considered in breeding programs nationwide.