Relationship between residual feed intake and carcass composition, meat quality and size of small intestine in a population of F2 chickens

Feed represent about 70% of the total costs in poultry production. These costs can be reduced by improving feed efficiency through genetic selection. Selection for improving feed efficiency may have correlated effects on other economically important traits such as carcass composition and meat quality. Therefore, the aim of the present study was to evaluate the relationships between the breeding values of cumulative residual feed intake (RFI) and carcass weight, carcass compositions, meat quality, and size of small intestines in chicken. The population studied was an F2 derived from a cross between an Arian fast-growing broiler line and Iranian native fowl. Individual feed intake and body weight measured every week from 2 to 12 weeks and carcass and meat quality traits were assessed after slaughtering at 12 weeks of age. Breeding values for cumulative RFI (RFIBV) were calculated using a quadratic spline with four knots and heterogeneous residual variance. Traits were analyzed using analysis of covariance with a model including RFIBV and sex. No significant relationship was observed between RFIBV with live body weight and eviscerated carcass weight (P > 0.05). RFIBV had negative association with breast muscle percentage, gizzard percentage and Ultimate pH of breast meat (P < 0.05). A positive relationship existed between RFIBV and abdominal fat percentage, skin percentage, lightness and yellowness of breast muscle color. No significant relationship was detected between RFIBV and back and neck, wing, liver, lung, spleen bursa and heart percentages. Also a non-significant association was observed between RFIBV and cooking loss percentage, shear force, drip loss percentage and small intestinal morphometric measurements. In general, the results suggest that selection on RFI will improve the feed efficiency of chickens without impairing carcass compositions and meat quality characteristics.