Detection of major genes affecting growth-related traits in a broiler chicken line

Abstract

In this study the body weight at birthday (BW) and at six weeks of age (BW6) in a commercial broiler chicken line, including 1555 roosters and 12142 hens, were analyzed to detect a single locus affecting growth-related traits by using the Major Gene Index (MGI) method. Based on the selection index method, the commercial broiler line was selected for 19 consecutive years in order to achieve gain in weight in the paternal line and reproductive traits in the maternal line. The goal was to investigate the deviation of offspring-predicted breeding values from parents-predicted breeding values using the MGI method. Trait means were 42.93 and 1861.5 g for BW and BW6, respectively. The MGI values for the entire population of the commercial broiler line at three levels of α (0.5, 1 and 2) were less than 1 (0.8, 0.72 and 0.77 for BW and 0.91, 0.78 and 0.85 for BW6). The MGI values for candidate individuals were greater than 1, and this index was also increased by the change of α (0.5-2). The results indicated that 8 of 65 roosters and 115 of 314 hens for BW trait, from 58 roosters and 714 hens as candidates for BW6 trait, 9 roosters and 216 hens were identified as major gene carriers. In conclusion, the MGI approach is suggested to be a useful preliminary step to detect major genes.