Molting is a natural process of many wild birds that occurs after the breeding season.
WHAT IS MOLTING?
Molting is a natural process of many wild birds that occurs after the breeding season. During molt, most feathers are replaced, bone structure is remodelled, and the immune system is rejuvenated. The female reproductive system regresses and is repaired during molting, which temporarily stops egg production. After molting, birds are in essence recharged and physiologically ready for another breeding season. This process is key to the long-term reproductive success of wild avian species.
How does molting relate to the industry?
In the commercial setting, the natural cues that trigger molting are not present, plus commercial breeding stocks have been genetically selected for production cycles that extend far beyond those of their natural cousins.
However, egg production does gradually decrease to the point where a flock is no longer economically viable. Turkey breeder stocks are generally replaced at this point. 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 outbreak, alternative means to maintain fertile egg production in the industry may be needed.
Molting is a procedure that could be used to reset’ a flock and gain a second production cycle after the first has ended.
THE PROBLEM
Traditional methods of molting commercial poultry involve severe water and feed restriction. While effective, these methods have serious animal health and welfare concerns and are discouraged in Canada. As an alternative, it has been shown that adding the hormone thyroxine to a chicken’s diet can induce molting. Dietary thyroxine mimics the hormonal changes that occur naturally during molt and thus helps to artificially trigger a molt without the need to restrict feed or water. Dr. Grégoy Bédécarrats at the University of Guelph and Dr. Robert Renema at the University of Alberta collaborated on a project to determine if this method could be adapted for use in turkeys.
A BETTER WAY
Several small flocks of commercial turkey breeders (kindly provided by Hybrid Turkeys) nearing the end of their production cycle were housed at the University of Guelph. Several trials were performed that showed thyroxine could indeed be used to induce molting in turkeys. The researchers then determined the minimum dose required to do so. Induction of molting alone, however, does not do the industry much good if the birds are unable to begin a new production cycle after molting. Drs. Bédécarrats and Renema determined that a period of reduced day length (achieved with artificial lighting) was required in addition to the thyroxine to completely reset the birds’ reproductive tract, thus allowing them to start a new production cycle.
After testing several combinations of thyroxine doses and lighting programs, the researchers concluded the preferred method of molting turkeys is to supplement their feed with 20 parts per million thyroxine and reduce photoperiod to six hours for 12 weeks. After this treatment, day length is increased back to 14 hours and the flock returns to lay in about eight weeks.
WHATS’S NEXT
The methods developed by Drs. Bédécarrats and Renema provide the turkey industry with a means to extend the productive life of breeder flocks in times when replacements are not readily available, without adversely affecting animal welfare.
While the preferred method described above is effective, it is likely to be expensive on a commercial scale. A more commercially viable procedure might use a cheaper, more readily available, source of thyroxine (the researchers suggest the possibility of using iodinated casein as a thyroxine precursor). The study also suggests that the treatment could incorporate a shorter holding period if sufficient thyroxine is present, which would bring the flocks back to lay sooner. Fine-tuning the methods may result in new management practices for modern turkey producers.
Funding for this research was provided by the Turkey Farmers of Canada, the Ontario Ministry of Agriculture, Food and Rural Affairs, and the Natural Science and Engineering Research Council.
For more details on any CPRC activities, please contact Gord Speksnijder at The Canadian Poultry Research Council, 483 Arkell Road, R.R. #2, Guelph, Ontario, N1H 6H8, phone: 289-251-2990, fax: 519-837-3584, e-mail: info@cp-rc.ca, or visit us at www.cp-rc.ca.
The membership of the CPRC consists of the Chicken Farmers of Canada, the Canadian Hatching Egg Producers, the Turkey Farmers of Canada, the Egg Farmers of Canada and the Canadian Poultry and Egg Processors’ Council. CPRC’s mission is to address its members’ needs through dynamic leadership in the creation and implementation of programs for poultry research in Canada, which may also include societal concerns.
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