Reaction norm models for the study of genotype × methionine + cystine level interaction in meat-type quail

• Published in: Livestock science 2019-11, Vol.229, p.56-63
• Main Authors: Gouveia, G.C., Ferreira, F., Abreu, L.R.A., Ribeiro, V.M.P., Rocha, B.M.M., Toral, F.L.B., Silva, M.A.
• Format: Article
• Language: English
• Subjects: Genetic evaluation; Genetic parameter; Reaction norm model
• ISSN: 1871-1413; 1878-0490
• DOI: 10.1016/j.livsci.2019.09.016

•Random regressions for weight gain in quails.•Legendre polynomials of distinct orders to study in the genotype × environmental interaction.•The genetic group influence the reaction norms behavior. The objective of this study was to use reaction norm models to study genotype × environment interactions of meat-type quails raised on different levels of digestible methionine + cystine. The weight gains of two meat-type quail strains (EV1 and EV2) were measured from 21 to 35 days of age. For EV1 strain the levels of digestible methionine + cystine were 0.60, 0.70, 0.80, 0.90 and 1.00%, for EV2 strain the levels were 0.61, 0.71, 0.81, 0.91 and 1.01%. Reaction norm models with Legendre polynomials (LP) varying from zero to four orders were tested, by using Bayesian methodology. The model of best fit was selected based on the criterions of Deviance Information and Posterior Model Probabilities (PMP). For the EV1 strain, the fourth-order LP model was the best fit for the weight gain description with different levels of digestible methionine + cystine for the mean trajectory, additive genetic effects and five classes of residual variance. For the EV2 strain, the first-order LP model was the best fit for the mean trajectory, fourth-order for additive genetic effects and five classes of residual variance. In both strains, genetic correlation estimates and reaction norm of the genotype in relation to dietary methionine + cystine indicated the existence of a genotype × dietary level of amino acids interaction. For EV1 strain, genetic correlations for weight gain in different levels of digestible methionine + cystine ranged from –0.98 to 0.84, while for EV2 strains these estimates varied from –0.98 to 0.94. Also, in general, for both strains the high density intervals of genetic correlations with 90% of samples included zero, indicating that genetic correlations between the weight gain in different levels of digestible methionine + cystine did not differed from zero. Furthermore, the reaction norms indicated that genotypes were not linearly related to tested dietary levels of amino acids. This absence of linearity implies that to verify the same response to selection in field that was predicted by the genetic evaluation, the nutritional levels used at the herds for selection candidates and their progenies must be the same.