Genotype x environmental interaction of growth traits to different levels of dietetic lysine for GIFT tilapia

The effect of genotype x environment interaction for dietetic lysine on Nile tilapia of the GIFT line body weight, daily and total weight gains at 150 days of age was evaluated in this study. The experiment was composed of 700 fish from 26 full-sib families. Each fish was uniquely identified with a microchip tag and randomly distributed in 5 different levels of dietetic lysine (1.43, 1.53, 1.63, 1.73, 1.83%), each level had 7 replicates. Random regression models with homogeneity and heterogeneity (2, 3, and 4 classes) of residual variance were used for the estimation of the genetic parameters. Those models were evaluated via the BIC and model probability criterions. In order to access the sensitivity of the breeding values to the dietetic lysine levels, reaction norms, genetic and Spearman correlations were estimated. The results pointed out the need to consider heterogeneity of residual variance. Significant genotype x environment interaction between the levels of dietetic lysine was identified for daily weight gain. Thus, the results are suggestive that the predictions of the breeding values for the traits evaluated at 150 days of age for Nile tilapia of the GIFT line must consider the level of digestive lysine in the diet used in the production system.