Date of Graduation

2008

Document Type

Thesis

Degree Type

MS

Committee Chair

Joseph Moritz

Abstract

In light of 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 using 1) a slow-growing and fast-growing genotype, 2) choice-feeding management, 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. Slowgrowing broilers (Gourmet Black) were raised from 1-84 days, and fast-growing broilers (Cobb 500) were raised from 1-56 days. The experiment was run during the grower and finisher phases in four different seasons: Late Fall, Spring, Summer, and Early Fall. Broilers were located on the West Virginia University certified organic farm, given access to pasture for at least eight hours daily, and exposed to natural fluctuations of environmental conditions. Replicate treatments were applied at the Animal Sciences farm, and included no access to pasture. No Choice (single diet) or Choice (corn offered in a separate feeder from rest of diet) feeding managements were implemented. Birds on no choice management showed higher Average Daily Gain (ADG) (P < 0.05) compared to choice managed birds. Slow-growing broilers had higher FCR and lower breast yield (P < 0.05) than the fast-growing genotype. Fast-growing no choice birds had higher breast yield than the choice birds of the same genotype (P < 0.05). Fast-growing genotypes were superior in performance and carcass characteristics compared to slowgrowing genotypes, and choice-feeding management did not improve performance or carcass characteristics. Performance was decreased in late fall, likely due to cold ambient temperatures.

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