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Motivation of Hens to Obtain Feed During a Molt Induced by Feed Withdrawal, Wheat Middlings, or Melengestrol Acetate¹

J. M. Koch^*, D. C. Lay, Jr., K. A. McMunn, J. S. Moritz and M. E. Wilson^*,2

^* Division of Animal and Nutritional Sciences, Davis College of Agriculture, Forestry and Consumer Sciences, West Virginia University, Morgantown 26506; and USDA-ARS Livestock Behavior Research Unit, Purdue University, West Lafayette, IN 47907

² Corresponding author: mwilso25{at}wvu.edu

Traditionally, molting was initiated by withdrawing feed. However, public criticism of feed deprivation, based on the perception that it inhumanely increases hunger, has led the poultry industry to ban the practice. Thus far, alternatives have not been demonstrated to ameliorate the increase in hunger that led to the ban on inducing molting by feed deprivation. Incorporating melengestrol acetate (MGA), an orally active progestin, into a balanced layer diet induces molting and increases postmolt egg quality. Hy-Line W-98 hens (n = 60) were randomly assigned to a balanced layer ration (control), a balanced layer ration containing MGA, or a 94% wheat middlings diet (wheat) for 20 d, or were feed deprived for 8 d. Hens were trained to peck a switch 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, abdominal fat pad and digesta-free gizzards were weighed. The number of pecks in the feed-deprived group was greater than controls by d 4 and remained greater at d 8, when these hens were removed from the experiment. Hens in the wheat group that were rewarded with a layer diet pecked more than controls from d 8 to 20. Hens in the MGA group pecked for a reward at the same rate as control hens throughout the experiment. Hens fed the wheat diet had heavier gizzards compared with control and MGA-fed hens. Hens fed MGA had greater abdominal fat pad compared with wheat and control hens. 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, hens molted with a wheat middling diet appear to be as motivated to obtain feed as did the feed-deprived hens.

Key Words: molting • hunger • laying hen • well-being • motivation

¹ This work is published with the approval of the Director of West Virginia Agriculture and Forestry Experiment Station as scientific paper. This project was supported by a USDA-ARS Specific Cooperative Agreement Agr #58-3602-1-172 and Hatch project 321 (NE 161). Disclaimer: The mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.