Synthetic Methionine and Feed Restriction Effects on Performance and Meat Quality of Organically Reared Broiler Chickens

Nutritionists have been challenged to find alternatives to synthetic methionine use in organic broiler diet formulation. Data do not exist on the ability of commercial broilers to partially meet amino acid requirements by foraging. In the current study, diets were formulated to include or preclude synthetic methionine (analyzed dietary methionine = 0.40 and 0.36%, respectively). Foraging ability was assessed by implementing 2 feeding strategies (ad libitum and restrictive feed access). The objectives of the study were 1) to determine performance, carcass characteristics, and meat quality effects of organically reared broilers fed diets with and without synthetic methionine and 2) to assess these variables when feeding strategies were modified to encourage foraging. Experimentation focused on broilers in the 3-to-8-wk growing phase and was conducted during 2 different times of the year (summer and fall). During the 0-to-3-wk starter phase, all diets contained synthetic methionine. The time of year and associated environmental conditions were observed to have an effect on feed intake and subsequent performance and carcass quality. Broilers reared in summer and fed diets without synthetic methionine demonstrated trends toward decreased gain to feed ratio and breast yield compared with broilers fed diets that included synthetic methionine. These trends did not exist for broilers reared in fall that had comparably increased feed intake. However, suggested growth impairments and compensatory feed intake associated with a marginal methionine deficiency were largely overcome by bird foraging. Feed restriction was shown to be an effective strategy to increase commercial broiler forage intake.