Effect of the slow (K) or rapid (k +) feathering gene on carcass-related traits of broiler chickens selected for breast and thighs weight

Abstract

This study was undertaken to evaluate the impact of slow/rapid feathering sex linked gene on carcass weight (CW) and yield (CY) as well as carcass main parts in an experimental colored broiler flock employing to evaluate the response to selection for breast and thighs weight with imposing restriction against low value portions of carcass over three generations. Random samples of the birds were slaughtered to evaluate the carcass traits at 42 days of age. Cut up yield was determined by partitioning each carcass to breast, thighs as high value parts and wings, neck, rack and saddle as low value portions (LVP). Live body weight (BW; 42d) and legs yield (LY) as a proportion of carcass weight (as %CW) were significantly greater for k+k+/k+W genotypes compared to K-/KW bearing birds (P<0.05). Inter sex t-test comparisons revealed significant superioty of k+k+ genotype over K- in male birds for LY (as %CW) and LY (as %BW) (P < 0.05). Inter family analysis for 8 larger half sib families revealed infrequent superiority of K-/KW bearing birds over their sibs with the alternate genotype for breast yield (BrY; as %CW), legs weight (LW) and LY (as %CW) in two families. Inter family and inter females analysis for 7 larger half sib families showed highly significant superiority for k+W birds in LW (as %CW), BW and LVW in two families (P<0.01). Considering feathering rate as a fixed effect (KW vs. k+W) to analyze the females data revealed significantly greater means for fast feathered females (k+W) for BW, CW, breast weight, LW and LVW than the alternate genotype (P<0.05). It is concluded that in the today's straight-run broiler flocks with numerous influencing factors of margin effects, and with increasing demands for uniformity of carcass market where sexable day-old chicks are not of interest, to launch the fast feathering gene (k+) could be of positive economic consequences in broiler production.