MOTIVATION OF HENS TO OBTAIN FEED DURING A MOLT INDUCED BY EITHER FEED WITHDRAWAL, WHEAT MIDDLINGS OR MELENGESTROL ACETATE

Authors: KOCH, J - WEST VIRGINIA UNIVERSITY; Lay Jr, Donald; McMunn, Kimberly; MORITZ, J - WEST VIRGINIA UNIVERSITY; WILSON, M - WEST VIRGINIA UNIVERSITY

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/13/2006
Publication Date: 4/17/2007
Citation: Koch, J.M., Lay Jr, D.C., Mcmunn, K.A., Moritz, J.S., Wilson, M.E. Motivation of hens to obtain feed during a molt induced by either feed withdrawal, wheat middlings or melengestrol acetate. Poultry Science. 86:614-620.

Interpretive Summary: The need for an alternative to feed withdrawal as a method to induce a molt has dramatically increased with the recent change to the United Egg Producers guidelines recommending that feed withdrawal no longer be used to induce a molt. The two most important factors in evaluating a potential alternative is that it allows for an increase in egg quality following the molt, and that the alternative does not increase hunger in the hen. Previously, we demonstrated that incorporating an orally active progestin into a balanced layer diet will cause reversible regression of the reproductive tract. Furthermore, both the internal and external quality of the eggs produced by hens molted utilizing MGA is dramatically increased compared to non-molted controls. In this study we add the final piece, demonstrating that utilizing MGA to induce a molt does not increase hunger in the molted hen, unlike alternatives that involve feeding bulk low nutrient density diets which increase hunger in the molted hen at least as much as in hens completely deprived of feed. These findings are critical for poultry companies and researchers, as it will allow them to design future molting diets that cause satiety in hens.

Technical Abstract: Traditionally, molting had been done by withdrawing feed, which leads to weight loss and increased mortality. Public criticism of feed withdrawal, based on the perception that it inhumanely increases hunger, has led the industry to ban the practice. Thus far, alternatives result in poor post-molt performance and they have not been characterized as to whether they ameliorate the perceived increase in hunger that led to the ban on feed withdrawal induced molt. Incorporating melengestrol acetate (MGA), an orally active progestin, in a balanced layer diet has been shown to induce molting and increase post-molt egg quality. Hy-Line W-98 hens (n = 60) were randomly assigned to either a balanced layer ration (control), a balanced layer ration containing MGA, 94% wheat middling diet (wheat) or received no feed for 8 d (non-fed). Hens were trained to peck a disk in order to receive a feed reward based on a progressive ratio reinforcement schedule. Motivation of hens to acquire feed was measured as the total number of pecks recorded in 15 min on d 0, 4, 8, 12, 16 and 20. On d 20, omental fat and digesta free gizzards were weighed. The number of pecks in the non-fed group was greater than controls by d 4 and remained greater at d 8 (P < .0001). Wheat hens, rewarded with a layer diet, pecked more than controls from d 8 to d 20 (P < .003). Hens in the MGA group pecked for a reward at the same rate as control hens throughout the experiment (P > .10). Hens fed the wheat middling diet had heavier gizzards as compared to the control and MGA hens (P > .01). MGA hens had greater omental fat compared to wheat and control hens P < .01). Hens molted using a diet containing MGA have a similar motivation to obtain feed as control hens; therefore, this alternative does not appear to increase hunger. However, those hens molted with a wheat middling diet appear to be as motivated as the non-fed hens to obtain feed.