Estudo de interação genótipo ambiente, via normas de reação, para características produtivas na raça Holandesa do estado do Paraná

Abstract

The reproductive animal biotechnology advances, such as artificial insemination, has enabled the diffusion of the same genetic material in different regions all over the world. From there, more studies of the genotype environment interaction have begun to be observed, since the genetic performance of some animals tend to modify according to the environment where it is being evaluated. The objective of this study was to investigate the presence of genotype-environment interaction, through reaction norm models, for the milk yield, fat yield and protein yield, in different regional temperatures in the state of Paraná, in animals of the Holstein cattle. Data from 67,360 primiparous cows belonging to the Paraná Holstein Breeders Association database were analyzed through official dairy control. It was adopted the random regression model for the analysis of reaction norms, assuming the residual variance as heterogeneous. The fourth-order evaluation under Legendre polynomial was applied to the analysis, assuming the mixed model of analysis by REML method through the WOMBAT software. After the full herd analysis, the genetic behavior of the 15 most representative bulls was evaluated, as the temperature gradient changes. The averages for Milk, Fat and Protein yield were 8,374.82 kg, 277.81 kg and 255.47 kg, respectively. Heritabilities ranged from 0.18 to 0.23, 0.21 to 0.27 and 0.14 to 0.20 for Milk, Fat and Protein yield, respectively, consistent with previous studies performed in Holstein Cattle in Paraná State. The correlation between temperature gradients for all traits was above 0.80 indicating an absence of significant interactions between genotype and environment. Despite of this, there were genetic modifications in the temperature increase, reaching a difference of up to 289 kg of milk, 10.69 kg of fat and 9.47 kg of protein, presenting specific modifications of the bulls according to the analyzed characteristic. From this information, it is concluded that it is not necessary the inclusion of temperature variable on genetic analysis model at Paraná Holstein Cattle.