Use of dietary thyroxin as an alternative moulting procedure in turkey breeder hens

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Moulting is a natural process which promotes the replacement of feathers at the end of a breeding season before migration. Since this physiological event is also required in-between reproductive cycles, artificial moulting techniques have been developed to induce a second egg-laying period in domestic birds. However, most methods are based on feed and water withdrawal, and although very efficient, such protocols result in severe stress and serious health and welfare problems. Thus, the use of this practice is discouraged in Canada and breeder flocks are replaced after each reproductive period. This has not been a problem, as long as replacement breeders are continuously available. However, disease outbreaks usually result in an immediate ban on bird movement, and would thus disrupt the fertile-egg supply chain, rapidly collapsing the entire industry. Force moulting might then be the only alternative. Nonetheless, due to animal health and welfare concerns, new effective, affordable, and acceptable alternatives to feed and water restriction techniques need to be established. Based on a preliminary trial performed in our research station and results obtained in caged chickens, dietary thyroxin supplementation can induce moult with minimal impacts on birds' health and welfare. However, in turkeys, the minimum dose required and the impact of dietary thyroxin on the second reproductive cycle still remain to be determined. Thus, this study aims at designing protocols to induce moult in spent turkey breeder hens using dietary thyroxin supplementation. In turn, results from this study will help develop new strategies that will be economically feasible and ethically acceptable to extend the reproductive life of turkey flocks.