Methionine is classified as an essential amino acid for poultry because it is needed to maintain viability, specifically for proper cell development and feathering. The National Organic Standards Board determined that while wholly natural substitute products exist, they are not presently available in sufficient supplies to meet poultry producer needs. Therefore, some allowance for synthetic methionine is necessary to comprise a nutritionally adequate diet for organic poultry.

Previously set to expire on 1 October 2012, the rule's effective removal of the date allows poultry producers to continue to use limited amounts of synthetic methionine at the following maximum levels after 1 October: laying and broiler chickens – 2 pounds per ton of feed; turkeys and all other poultry – 3 pounds per ton of feed.

The final rule addresses the second of a two-part recommendation by the National Organic Standards Board, an independent body of organic industry and stakeholder representatives that evaluates materials that are petitioned to be allowed or prohibited in organic agriculture. The first part of the Board's recommendation was codified in October 2010 to allow organic poultry producers to prepare for reduced levels of synthetic methionine allowed in feed, effective with the publication of the final rule.

Carrying out the second part of the recommendation, the rule provides for basic maintenance requirements while urging the organic poultry industry to continue to find commercially sufficient yet allowable natural methionine sources.

The change in methionine requirements will be reflected on the National List of Allowed and Prohibited Substances, a subpart of the USDA's organic standards that identifies synthetic substances that may be used and non-synthetic (natural) substances that may not be used in organic production. The Organic Foods Production Act of 1990 and NOP regulations specifically prohibit the use of any synthetic substance in organic production and handling unless the synthetic substance is on the National List. Under the authority of the governing law, the Secretary of Agriculture can amend the National List based on recommendations by the National Organic Standards Board. The Board makes their recommendations according to technical evaluations based on several key factors, including potential impact on human health and the environment, essentiality, and compatibility and consistency with organic production and handling standards.

USDA has funded several research projects aimed at breeding organic feed corn with higher levels of natural methionine and also concerning poultry management strategies to reduce the need for supplemental methionine. Further research is still needed and encouraged in research grant applications.

The final rule will become effective on 2 October 2012. The rule will also correct the Chemical Abstracts Service (CAS) numbers for the listing for synthetic methionine on the National List.