ESTUDO DA INTERAÇÃO GENÓTIPO X AMBIENTE SOBRE CARACTERÍSTICAS PRODUTIVAS NA RAÇA HOLANDESA EM DIFERENTES REGIÕES DO PARANÁ

Abstract

The wide use of artificial insemination has favored that different genotypes be distributed in different regions around the world. The lack of adaptation to some environmental conditions can cause an effect called genotype x environment interaction, mainly in polygenic characteristics, with changes in genetic parameters. The objective of this study was to evaluate the genotype x environment interaction through genetic correlations for milk yield (MY), milk fat yield (FY) and milk protein yield (PY). A total of 57,967 primiparous cows with lactations between 1990 and 2015 and a relationship matrix of 106,848 animals were used to estimate the genetic correlation between three regions of different climates. The database used belongs to the Associação Paranaense de Criadores de Bovinos da Raça Holandesa- APCBRH and was divided by region according to the climatic classification in, R1) mesothermic climate moist and super humid, R2) mesothermic climate without dry season, R3) mesothermic climate with dry season. The effects included in the model were fixed effects of the contemporary group (herd and year of birth), as covariate the age at birth and the additive genetic effect as random effect. The genetic parameters were estimated by the REML method, using the VCE 6.0 program. To obtain the genetic values, the PEST2 program was used, in which the bulls were later classified and submitted to the Pearson and Spearman correlations, respectively. The coincident animals between the regions were verified, considering the bulls 10% better classified of each region for the accomplishment of the statistical comparison. The heritability between the regions ranged from 0.16 to 0.21 for MY, from 0.17 to 0.25 for FY and from 0.10 to 0.17 for PY. Genetic correlations, Pearson correlations, Spearman correlations and percentage of coincident animals for the three characteristics between regions were all higher than 0.90 and therefore close to one. The results obtained demonstrate that there is no interaction genotype x environment for the three characteristics evaluated within the distinct climatic classifications in Paraná. That is, the estimation of the genetic value of an animal in one region may also be used for another region, without significant bias in the genetic progress of the trait. Moreover, since there was no significant change in genetic prediction between regions of Paraná, only one selection program could be adopted, which would include all the herds of the state of Holstein, reducing their cost and time.