GH-mRNA expression and prediction of genetic improvement using selection index for body weight traits in turkeys

Abstract. This study aimed to evaluate the expected responses to a selection index based on body-weight-related traits to improve the productive performance of turkeys and to investigate the relationship between body weight and growth hormone (GH) gene expression. Two lines of local Baladi turkeys were used: a selected line (S), chosen for high body weight at 6 months of age; and an unselected random-bred control line (C). Both lines originated from the same randomly mated base population. A selection index incorporating body weight (BW), shank length (SL), and breast width (BRW) at 6 months of age was constructed. This index resulted in expected genetic gains per generation of 441.71 g for BW, 0.26 cm for SL, and 1.93 cm for BRW. Growth hormone gene expression in the selected line was significantly higher than in the control line for both sexes. In males, GH showed a relative gene expression of 1.43 in the selected line compared with 1.01 in the control line, while in females, the corresponding values were 1.76 and 1.31, respectively. Differences in GH-mRNA expression between the two lines indicate a positive association between gene expression level and body weight, suggesting that GH expression may be a useful molecular marker in genetic selection programs aimed at improving body weight in turkeys.