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The effect of genotype, choice feeding, and season on organically reared broilers fed diets devoid of synthetic methionine

Division of Animal and Nutritional Sciences, West Virginia University, Morgantown 26506-2008

¹ Corresponding author: Joe.Moritz{at}mail.wvu.edu

In response to the impending ban on synthetic methionine in organic poultry diets, researchers have focused on finding alternative strategies to supply this amino acid. The objectives of this study were to assess performance and carcass characteristics of broilers fed diets devoid of synthetic methionine by using 1) a slow-growing and a fast-growing genotype, 2) choice-feeding management (supplying grain and a complementary premix in 2 separate feeders), and 3) pasture access and seasonal variation. Inclusion of fish meal and high percentages of soybean meal enabled the specific genotype methionine requirement to be met. All diets were certified organic. The experiment was conducted during the grower and finisher phases in 4 different seasons: late fall, spring, summer, and early fall. Pasture access was assessed either by housing broilers on the West Virginia University Organic farm and giving them outdoor access, or by housing broilers on the West Virginia University Animal Sciences farm and giving them no outdoor access. Fast-growing genotypes were superior in performance and carcass characteristics compared with slow-growing genotypes, and choice-feeding management did not improve performance or carcass characteristics. Pasture access tended to have no effect on slow-growing broilers and decreased the performance of fast-growing broilers. Performance was decreased in late fall, likely because of cold ambient temperatures.

Key Words: methionine • broiler • organic