Molting (reproductive rejuvenation) of poultry to extend table or fertile egg production is a well accepted commercial practice in the U.S. However, the conventional method of ~10-day feed withdrawal to induce molt is increasingly viewed as unacceptable by McDonald's, Wendy's, AVMA, and the egg consuming public. The use of dietary L-thyroxine (T4; the natural molting hormone) for poultry can provide an effective commercial method of inducing molting while providing full access to treated feed and water. These studies will gather further information on the feasibility of the concept and how it should be carried out in chickens and turkeys to extend egg production, improve profitability, and assure animal welfare. OBJECTIVES: Live poultry will be used to conduct feeding trials with L-thyroxine from supplemental dietary levothyroxine (L-thyroxine) and/or thyroactive iodinated casein to compare this method with conventional 10-day feed withdrawal molting (reproductive rejuvenation) to extend table or fertile egg production. Caged laying hens, broiler breeder hens, and turkey breeder hens will be evaluated in separate trials, but information will be obtained from results about species similarities and differences. Other goals will be to determine the iodine content of eggs collected during the molting procedures, to obtain blood samples for counting heterophil / leukocyte ratio as an indicator of level of stress, to measure body weight loss and extent of regression of ovaries and oviduct, and in some studies to determine subsequent live performance of hens following the molting process. APPROACH: Small scale studies will be conducted at 4 locations in AR (broiler breeder hens), NC (turkey breeder hens, 2 sites), and VA (caged laying hens) to further assess the feasibility of the concept of using L- thyroxine in the feed of poultry to induce molting (cessation of egg production, feather loss, body weight reduction, regression of ovaries and oviduct) while allowing full access to treated feed and water. The conventional 10-day feed withdrawal method will be used as a control procedure. The FDA allows investigational products (test articles) such as L-thyroxine and thyroactive iodinated casein to be shipped interstate for study purposes and for trials to be conducted with live poultry as long as accurate, complete, and detailed records are kept (Title 21, CFR 511.1a). However, no eggs or poultry meat can go into the human food chain and all leftover birds and feed must be disposed of by incineration or landfill. These studies will help develop a patent pending commercial method of molting to extend egg production
