The effectiveness of an SNP marker in the cholecystokinin type A receptor gene for improving growth traits in Amakusa Daioh cross chickens

Summary: Amakusa Daioh cross chickens from Kumamoto Prefecture, Kyushu Island, Japan, are F1 hybrid chickens resulting from a cross between the Amakusa Daioh and Kyushu Rhode breeds. A significant association has been reported between a SNP (AB604331, g.420 C>A) in the cholecystokinin type A receptor gene and growth traits in some Japanese slow-growing chickens. This genetic improvement effect was examined in Amakusa Daioh cross chickens by comparing superior A allele-fixed chickens with conventional ones. Fattening experiments using 436 conventional and 297 improved (A allele-fixed) Amakusa Daioh cross birds were performed over two seasons. In each season, experimental birds of both sexes were hatched on the same day, raised in the same chicken house, and fed the same diet ad libitum for 15 wk for cockerels and 19 wk for pullets, after which they were slaughtered. Body weight (BW), average daily gain (ADG), and carcass weights were measured. SNP genotypes were determined using mismatch amplification mutation assay. Association between the SNP and growth traits was analyzed using GLM, taking into account gender, season, genetic additive and dominance, and test group effects. The improved pullets were significantly heavier than the conventional pullets at slaughter age. Boneless carcasses of the improved pullets were significantly heavier than those of the conventional pullets as well. In the conventional cockerels, significantly positive additive effects of the A allele on BW were detected during the entire experimental period, except at 10 and 11 wk. Significantly positive additive effects of the A allele on thigh weight were detected. We concluded that g.420 C>A is a good selective marker for increased slaughter live weight and meat weight in Amakusa Daioh cross chickens