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

蜕皮是一个自然的过程，在迁徙前的繁殖季节结束时，它会促进羽毛的更换。由于这一生理过程在繁殖周期之间也是必需的，人工换羽技术已经被开发出来，以诱导家禽的第二个产卵期。然而，大多数方法都是基于取食和取水，虽然非常有效，但这种方案会导致严重的压力和严重的健康和福利问题。因此，加拿大不鼓励使用这种做法，每个繁殖期后都会更换种鸡群。这不是问题，只要有后备的饲养员就可以了。然而，疾病的爆发通常会导致立即禁止禽类活动，从而扰乱受精卵供应链，迅速崩溃整个行业。到那时，强制换羽可能是唯一的选择。然而，出于对动物健康和福利的担忧，需要建立新的有效、负担得起和可接受的替代饲料和限水技术。根据在我们研究站进行的初步试验和在笼养鸡身上获得的结果，日粮中补充甲状腺激素可以诱导换羽，对禽类的健康和福利影响最小。然而，在火鸡中，所需的最低剂量以及饮食中甲状腺激素对第二生殖周期的影响仍有待确定。因此，这项研究旨在设计方案，通过在日粮中添加甲状腺激素来诱导废弃火鸡种鸡的蜕皮。反过来，这项研究的结果将有助于开发新的战略，这些战略将在经济上可行，在伦理上可以接受，以延长火鸡群的生殖寿命。

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.