RECENT ADVANCES IN INDUCED MOLTING

Molt induction methods that produce a complete cessation of lay, reproductive involution for several days, and loss of nearly 50% of the primary feathers are the most successful. Feed deprivation and high levels of dietary zinc have proven to be the most consistent methods available. Calcium appears to play a pivotal role in molt induction as calcium carbonate feeding prolongs ovulation during the initial stages of an induced molt and dietary zinc has been shown to interfere with calcium-related metabolic activities at the level of the ovary. The primary site of action of feed deprivation appears to be at the level of the hypothalamic-hypophyseal axis, where calcium is involved in many endocrine pathways. The physiological basis of postmolt rejuvenation has been related to the extent of ovarian and oviducal involution. Evidence suggests that restructuring of receptor or membrane functions in the oviduct is the basis for rejuvenation. A body weight loss of about 30% appears to be necessary for appropriate restructuring of the shell gland.