R. Bras. Zootec.01/Mar/2009;38(3):467-73.
Genotype × environment interaction for milk yield of Holstein cows among dairy production units in the state of Paraná
DOI: 10.1590/S1516-35982009000300010
It was analyzed 117,082 complete lactation records adjusted for 305 days in milk yield (MY305) of 49,676 Holsteins cows from 308 herds distributed among seven dairy production units in the state of Paraná, Brazil. The objective was to verify the genotype × environment interaction to MY305 of Holsteins cows between dairy production units in the state of Paraná using the Bayesian inference. All animals were officially controlled by the Serviço de Controle Leiteiro Mensal of Associação Paranaense de Criadores de Bovinos da Raça Holandesa, between January/1992 and December/2003. The (co)variance components and genetic parameters were estimated using one and multiple-trait analysis, where MY305 of each dairy production unit was considered as a different variable. Means and standard deviations for MY305 (kg) for dairy production units of Castro, Carambeí, Witmarsum, Arapoti, Sul, Norte and Oeste, were 8,414 ± 1,825; 8,481 ± 2,010; 7,636 ± 1,594; 7,850 ± 1,795; 8,617 ± 2,050; 7,401 ± 1,809 and 7,336 ± 2,456, respectively. The highest heritability estimated was obtained for the Oeste unit (0.39) while Carambeí unit presented the lowest value (0.23). Genetic correlations were low (0.09 to 0.57) between dairy production units. Pearson and Spearman correlations were lower for the Oeste unit, when compared with other dairy production units, which ranged from 0.37 to 0.41, and from 0.37 to 0.49, respectively. These results show the presence of genotype × environment interaction between dairy production units in the state of Paraná.