Genotype×dietary (methionine+cystine):Lysine ratio interaction for body weight of meat-type quails using reaction norm models.

Our objective was to evaluate the effect of genotype by environment (G×E) interaction for body weight (BW) of meat-type quails ( Coturnix coturnix ) during the growing period using two strains (LF1 and LF2) to changes in the dietary (methionine+cystine):lysine ([Met+Cys]:Lys) ratio. A total of 4512 records, collected during the initial phase (day 14 and 21), and final phase (day 28 and 35), was used for analyses. During the initial phase, quails were fed diets with increasing (Met+Cys):Lys ratios (0.61, 0.66, 0.71, 0.76, and 0.81), containing 26.1% crude protein (CP) and 2900 kcal ME/kg; and during the final phase, quails were fed a single diet containing 22% CP and 3050 kcal ME/kg. A single-trait animal model, including sex as the fixed effect, (Met+Cys):Lys ratio as the control variable, and breeding value as the random effect, was utilized for analyses. The Legendre polynomial of second order was utilized for the analysis of the G×E (nutritional levels) interaction using reaction norm. Genetic variance and heritability estimates varied according to the nutritional gradient. The LF2 strain had greater sensitivity to changes in the dietary (Met+Cys):Lys ratio compared with LF1, and greater residual effect of diets provided during the initial phase of the growing period. Genetic evaluations for quails fed different dietary (Met+Cys):Lys ratio provided changes in the predicted BW breeding values. We conclude that selection population must be fed with same dietary (Met+Cys):Lys ratio that commercial populations are fed. [ABSTRACT FROM AUTHOR]