Genotype-by-environment interaction across THI classes impacts the selection for body weight at young ages in meat quails.

This study aimed to investigate the impact of genotype-by-environment interaction (GEI) on body weight (BW) in meat quails. BW data from ten generations, recorded on 7 (BW7), 14 (BW14), 21 (BW21), 28 (BW28), 35 (BW35), and 42 (BW42) days after hatching were used for the analyses. A temperature and humidity index (THI) divided into two classes (less or equal than 68 - THI1 and greater than 68 -THI2) was used as the environmental descriptor. Variance components and genetic parameters, including heritability and genetic correlation estimates, were computed for BW considering these two classes of THI. The rank correlation coefficients and percentage of individuals in common in the top 1 % animals (classified by breeding values in THI2) for BW were calculated. Also, the top 10 % with at least 13 offspring and the pattern of the top 10 breeding value animals were analyzed across THI classes. The heritability estimates ranged from 0.22 (for BW42 at THI1) to 0.49 (for BW28 and BW35 at THI1). In addition, the genetic correlations ranged from 0.16 (for BW7 between THI1 and THI2) to 0.98 (to BW42 between THI1 and THI2). The genetic correlation between THI1 and THI2 was low for BW7 (0.16), moderate for the two following weeks, i.e., BW14 and BW21 (0.65 and 0.55, respectively), and high for BW28, BW35, and BW42 (0.94, 0.98, and 0.96, respectively). The rank correlations indicated reranking of younger birds (BW7, BW14, and BW21), reflecting variations in breeding values across THI classes. The quails kept their ranking position from 28 days onwards when comparing the evaluated THI classes. However, younger birds, before 28 days, exhibited reranking across the different THI ranges. This study reinforces the relevance of the effect of THI on animal performance, highlighting the need to consider them in analyses for selecting superior and more resilient animals.