Performance, Livability, and Carcass Yield of Slow- and Fast-Growing Chicken Genotypes Fed Low-Nutrient or Standard Diets and Raised Indoors or with Outdoor Access.

Two experiments were conducted to assess the effect of genotype, production system, and nutrition on performance and livability of meat chickens for niche markets. Slow-growing (SG) and fast-growing genotypes (FC) were raised for 91 and 63 d, respectively, in experiment 1 (females) or 84 and 56 d, respectively, in experiment 2 (males). In each trial, SC were placed before FG to achieve a similar BW at processing. In experiment 1, each genotype was assigned to 8 pens of 20 birds each, with 4 pens within each genotype raised indoors in a conventional research facility or in a small facility with outdoor access. All birds were fed a low-nutrient diet. In experiment 2, genotype assignment to pens was as in experiment 1; however, 4 pens within each genotype were fed a low-nutrient diet or a conventional diet, and birds were raised indoors. Birds were gait-scored and commercially processed; legs were examined for tibial dyschondroplasia lesions and scanned for bone mineral density. In experiment 1, FC gained more weight than SC (P < 0.05) even though they were placed later. Outdoor access increased feed intake, and feed efficiency was poorer (P < 0.05). Fast-growing genotypes had higher breast meat yield, whereas SC had higher wing and leg yields (P < 0.05). In experiment 2, the low-nutrient diet reduced (P < 0.05) gain of the SC; FC increased feed intake of the low-nutrient diet such that their gain was unaffected (P > 0.05). For FC, the low-nutrient diet resulted in a poorer (P < 0.05) feed efficiency. Although weight gain of the FC was maintained on the low-nutrient diet, breast yield was reduced (P < 0.05). Cenotype affected bone health in both experiments, with SC having better gait scores and less tibial dyschondroplasia (P < 0.05). Outdoor access and the low-nutrient diet also resulted in better gait score (P < 0.05). These data indicate differences among genotypes and provide information about the efficiency and potential for alternative poultry systems. [ABSTRACT FROM AUTHOR]