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CTM022

2007 - 2009

Use of dietary thyroxine as an alternative molting procedure in turkey breeder hens

Principal Investigator: Grégoy Bédécarrats, University of Guelph
Status: Completed

Objective

  1. To determine if a relatively high does (40 ppm) of thyroxin will induce moulting in turkey hens with minimal impacts on the birds’ health and welfare.
  2. To determine if turkey hens treated with thyroxin can enter a second reproduction cycle.
The long-term objective of this research program is to develop moulting protocols that would be applicable on a large scale and would be ethically acceptable to both the industry and the public.

Background

Although genetic selection has dramatically increased egg production of the modern breeder chicken hen, similar strides have not been made for turkey breeders. As a result, turkeys breeder stocks are replaced as their egg production declines. This approach works within the industry only when replacements are in sufficient supply. In times when supply is cut off, such as when bird movement restrictions are imposed during a disease break, alternative means to maintain fertile egg production in the industry may be needed. Moulting is a procedure that could be used to ‘reset’ a flock and gain a second production cycle after the first has stopped. Traditional methods of severe light, water and feed restriction are effective in inducing a moult, but have serious welfare concerns. As an alternative, dietary supplementation with thyroxin has been used successfully in chickens. This aim of this project is to determine if this method could be adapted to turkeys.

Research Progress

A preliminary trial shows that dietary supplementation with 40 ppm thyroxin for 10 days will induce moulting in end-of-cycle turkey hens. Thyroxin treatment results in lower feed intake and reduction in body weight coupled with egg production that decreases to zero within 25 days of treatment. Following treatment, hens resumed or exceeded pre-treatment feed consumption levels and returned to their initial body weights. By the time the trial was terminated at day 37 (27 days after thyroxin treatment stopped), most treated hens had replaced feathers lost during the moult cycle and several treated hens began to lay eggs again. Reducing photoperiod to 6 hours of light per day (vs. 14 hours) appeared to induce moult more rapidly. No adverse effects of the treatment were noted during the trial.

Future Work

A dose response trial is planned to determine the minimum dose of thyroxin that will induce moulting and to determine if treated hens can return to a reproductive cycle. The trial will also test the effect of “holding” the treated flocks with 6 hours of light for 6 or 12 weeks on subsequent egg production. Levels of thyroxin and corticosterone in plasma samples collected during this and the previous trial will be measured.

Funding

$78,816 ($39,495 Canadian Turkey Marketing Agency (Turkey Farmers of Canada), $4,080 Hybrid Turkeys (in kind), $18,455 NSERC, $16,786 OMAFRA)

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