Diversidade genética e associação do gene do choque térmico (HSP-70.1) ao desempenho produtivo em vacas leiteiras no semiárido

Abstract

Heat stress is a factor that contributes to the reduction of productivity of dairy cows around the world. The demand for animals adapted to produce best in environments that present temperatures which can lead to heat stress is an aspect of great importance for dairy production in Brazil. The objective of this study was to evaluate the genetic diversity of HSP-70.1 gene and associated polymorphisms found for production performance of dairy cows in the Brazilian semiarid region. The study was conducted with purebred Holstein, Girolando (5/8 H-G) and Sindi, belonging to herds managed by the Agronomic Institute of Pernambuco, Experimental station of São Bento do Una and Arcoverde and the Brazilian Agricultural Research Corporation - Petrolina respectively. Initially was held the collects of biological material, then the extraction of DNA, gene amplification, digestion with restriction enzymes (EcoRII) followed by electrophoresis and photo documentation. We evaluated the genetic variability, the standard diversity index and the analysis of molecular variance between and within herds. Then it verified the association of polymorphisms on milk production traits. The results allowed the identification of seven polymorphisms with some standards being shared among the herds. The greatest similarities were found between the standards of the Holstein and Sindi cattle. The genetic differentiation index observed high levels of differentiation both between and within herds. Through variance analysis identified the factors that influenced in average production. Significant differences for the variable milk production were observed through the multiple comparison test of means, with the herds presenting different patterns of higher polymorphisms. Knowledge of the genetic variability of HSP-70.1 gene is to greatly contribute to the state of cattle milk, supporting the rise of racial pattern of herds and enabling the exploitation of the different responses provided under conditions of heat stress.