Current and Future Prospects for Induced Molting in Layer Hens

s of papers 67 283 Physiology and behavior of the hen during an induced molt. A. B. Webster*, The University of Georgia, Athens, Georgia. Feed deprivation is used commercially to induce molt because it is the easiest method to apply and produces the best results. Animal welfare concerns have made it important to evaluate the experience of hens undergoing feed deprivation. Birds of diverse species appear to have the same three-phase response to long term fasts, whether naturally occurring or artificially imposed. The first phase lasts a few days at most during which physiological and behavioral adjustments reduce protein catabolism and energy expenditure. A temporary increase in plasma corticosterone may be observed. Corticosterone promotes gluconeogenesis, helping to maintain plasma glucose levels in the initial stage of the fast. Corticosterone also appears to promote increased activity at this time, consistent with the increased levels of alertness and activity seen in hens during the first 48 h of feed deprivation. Aggressive behavior at the feeder may increase briefly among hens the first day of feed deprivation. In the second phase of fasting, protein is spared and lipids are mobilized to provide energy. This phase may last several months in some birds; in the chicken it can continue more than 20 days. Hens show increasing resting behavior during this phase. The third phase is marked by acceleration of protein catabolism. A pathological stage is eventually reached when the bird ceases activity and will not eat if given food. This phased response to feed deprivation trades off the need to maintain levels of plasma glucose to sustain activity and the need to maintain critical body structures such as muscles and organs. The strategy succeeds in that healthy hens retain strength and vigor throughout feed deprivation periods typical of induced molt programs. Hens having undergone extended fasts may also have improved livability. Alternative induced molting methods are being sought to reduce animal welfare concerns. The methods currently receiving the greatest interest involve alteration of a hen#s feeding regimen and cause at least some body weight loss. Any such alternative induced molt program should be verified not to make hen welfare actually worse by causing perception of feed restriction without allowing full progression into the second phase of fasting adjustment.