Using dietary thyroxine to induce molting in turkey hens

What is this research about?

Molting in birds is characterized by the loss and regrowth of feathers. Molting has an effect on the reproductive system of the bird. Molting allows birds to maintain their reproductive health throughout their lives. In the poultry industry molting is used to get a second or third egg-laying cycle. This has economic benefits for the farmer because they do not need to replace their flock with younger birds as often.

Currently, turkey hens may be restricted from feed and water to induce molting. This practice can cause severe stress and serious health and welfare concerns. In Canada this practice is highly discouraged.

Dietary supplementation of thyroxine with a reduction in photoperiod has successfully induced a complete molt in chickens. Thyroxine (T4) is a form of thyroid hormone that has a role in controlling metabolism. The purpose of this study was to determine if a relatively high dose of dietary T4 could induce a complete molt in spent turkey breeder hens.

What did the researchers do?

This summary is a project of the Institute for Community Engaged Scholarship (ICES) at the University of Guelph, with project partners: the Business Development Office (BDO), SPARK Program at the University of Guelph, and Knowledge Mobilization Unit at York University. This project is part of the Pan-Canadian Research Impact Network.

The researchers gave turkey hens 40ppm T4 for 10 days and observed for another 27 days. There were three treatment groups plus a control group (treatment A). Group B received 14 hours of light a day. Group C received 14 hours of light during for the 10 days of supplementation, and 6 hours of light after day 10. Group D received 6 hours of light a day. The factors measured included: feed intake, body weight, egg production, molting, and behaviour.

What did the researchers find?

Dietary thyroxin supplementation was successful in inducing a molt in turkey hens as in chickens. Most hens treated with T4 started molt within 8 days of receiving the supplements and finished molt by day 37. Thyroxin supplementation significantly reduced the feed consumption in all treated groups by at least 56 to 69%. Reduced feed intake was most likely voluntary as a result of a decreased appetite rather than feed avoidance. Thyroxin supplementation resulted in significant rapid body weight loss in all treated groups. Thyroxine supplementation for 10 days did not induce hyperactivity or stress and did not induce noticeable heat stress due to increased metabolism. At the end of the trial, no abnormal levels of T4 were observed. This shows that use of dietary thyroxin is safe.

What you need to know:

Dietary thyroxin supplementation was successful in inducing a molt in spent turkey breeder hens. This process can provide economic bene-fits to farmers and does not cause stress or serious health and welfare concerns to the turkeys like other procedures.

How can you use this research?

Turkey producers can use this research to guide their practices to in-duce molting in their flocks.
Poultry policymakers and govern-ment organizations can use this research to ensure policies and recom-mended practices are evolving with the evidence towards more economically sustainable and animal welfare-friendly procedures.

About the Researchers:

Dr. Gregoy Bedecarrats is an Associate Professor with the Department of Animal and Poultry Science at University of Guelph. Dr. Bedecarrats can be reached by email at Article citation: Gulde, V.A.L., Renema, R., and Bedecarrats, G.Y. (2010). Use of dietary thyroxine as an alternative molting procedure in spent turkey hens. Poultry Science, 89:96-107.

Cite this work:

University of Guelph, Institute for Community Engaged Scholarship (2011). Using dietary thyroxine to induce molting in turkey hens. Retrieved from:



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POSTED: Oct 6, 2011

Posted in News, News Bedecarrats.