Joy A. Mench
Department of Animal Science
University of California
Davis, California 95616-8532
Paul B. Siegel
Department of Animal and Poultry Sciences
Virginia Polytechnic Institute and State University
Blacksburg, Virginia 24061-0306
The past decade has seen an increasing trend in the recycling of layers through induced molting. In birds, plumage is normally replaced before sexual maturity. This process, called molting, also occurs after sexual maturity and is associated with a pause in egg production, which can be lengthy if birds are permitted to molt naturally. Inducing hens to molt rapidly extends their productive life and has become a common procedure in the recycling of layers.There is considerable literature on induced molting (11). Techniques used to induce molt include feed restriction; a change in light cycle; manipulation of dietary ingredients such as calcium, iodine, sodium, and zinc; and administration of pharmaceutical compounds that influence the neuroendocrine system, sometimes coupled with a reduction in photoperiod. These procedures cause an abrupt cessation of egg production coupled with loss of body weight and feathers. Restoration of egg production is accomplished by initially feeding a diet designed to meet the nutritional requirements for a non-ovulating, feather-growing hen, followed by feeding a normal laying hen ration.
The most common procedure used to induce molt is feed withdrawal. Its popularity as a molting method is probably due not only to its efficacy, but to the elimination of feed costs during the withdrawal period. Unfortunately, there is a paucity of data on the well-being of hens during the withdrawal and postwithdrawal periods, although feed deprivation is known to result in both increases in stress hormones and behavioral changes in poultry (1). Until more information is available, programs that minimize the length of the feed withdrawal period (7) should be used whenever possible.