Induced molting (or forced molting) is the practice by the commercial egg industry of artificially provoking a complete flock of hens to molt simultaneously. This is usually achieved by withdrawal of feed for 7-14 days. During the molting period, the hens go out of production for a period of at least two weeks. This has the effect of allowing the hen's reproductive tracts to regress and rejuvenate. After a molt, the hen's production rate usually peaks slightly below the previous peak rate and egg quality is improved. The point of molting is thus to increase the production, egg quality, and profitability of flocks in their second or third laying seasons. Flocks that are slaughtered after a single laying season are not molted. In the UK, the Department for Environment, Food and Rural Affairs states In no circumstances may birds be induced to moult by withholding feed and water.
Molting simulates the natural process where chickens grow a new set of feathers in the fall, a process generally accompanied by a sharp reduction or cessation of egg production. Natural molting is stimulated by shortening day lengths combined with stress (of any kind). Before confinement housing with artificial lights were the norm, the fall molt caused a fall scarcity of eggs and high market prices. Farmers attempted to pamper their flocks to prevent the molt as long as possible, to take advantage of the high prices. Modern controlled-environment confinement housing has the opposite problem; the hens are not normally presented with sufficient stress or cues to go into molt on their own. However, after laying continuously for nearly a year, their rate of egg production declines, as does the quality of the eggshell and the egg contents. In addition, the hens are seriously overweight.
For a complete recovery of the reproductive tract the hen's body weight must drop 30 to 35 percent during the molt. This is achieved by withdrawing the hen's feed for 7-14 days or up to 28 days under experimental conditions which presumably reflect standard farming practice in some countries. This means the hens lose their feathers and cease to lay eggs in addition to losing weight. Some die during forced molting; North and Bell insist that the flock must be managed so that mortality does not exceed 1.25% over the 1–2 weeks of (nearly complete) feed withdrawal, compared to a 0.5% to 1.0% monthly mortality in a well-managed flock under low-stress conditions. In 2003, more than 75% of all flocks in the US were moulted.
Molting programs follow many variations. Some do not eliminate feed altogether but may induce a moult by providing a low-density diet (e.g. grape pomace, cotton seed meal, alfalfa meal) or dietary manipulation to create an imbalance of a particular nutrient(s). The most important among these include manipulation of minerals including sodium (Na), calcium (Ca), iodine (I) and zinc (Zn), with full or partially reduced dietary intakes. Some programs combine feed withdrawal with a short period of water withdrawal. Most programs also restrict the amount of lighting to provide a daylight period that is too short to stimulate egg production, providing a simulated autumn, the natural time of molt and minimum egg production.
Forced molting is not a common practice in Canada, where the animal welfare issues associated with it has rendered it basically obsolete.
This temporary starving of the hens is seen as inhumane and is the main point of objection by critics and opponents of the practice. The alternative most often employed is to slaughter the hens instead of molting them.
It is sometimes claimed that forced molting is an artifact of factory farming, but, like virtually all poultry practices, it predates the vertical integration of the poultry industry by decades. Former Head of the Poultry Science Department at the University of Maryland, Morley A. Jull prescribes a precise molting program in his 1938 book, Poultry Husbandry.
- Molino, A.B., Garcia, E.A., Berto, D.A., Pelícia, K., Silva, A.P. and Vercese F., (2009). The effects of alternative forced-molting methods on the performance and egg quality of commercial layers. Brazilian Journal of Poultry Science, 11: 109-113
- Webster, A.B., (2003). Physiology and behavior of the hen during induced moult. Poultry Science, 82: 992-1002
- North, Mack O. and Bell, Donald D, Commercial Chicken Production Manual, 4th ed., 1990. Van Nostrand Reinhold, pp. 438)
- Yousaf, M. and Chaudhry, A.S., (2008). History, changing scenarios and future strategies to induce moulting in laying hens. World's Poultry Science Journal, 64: 65-75
- Patwardhan, D. and King, A., (2011). Review: feed withdrawal and non feed withdrawal moult. World's Poultry Science Journal, 67: 253-268
- Khan, R.U., Nikousefat, Z., Javdani, M., Tufarelli, V. and Laudadio, V., (2011). Zinc-induced moulting: production and physiology. World's Poultry Science Journal, 67:497-506. doi:10.1017/S0043933911000547
- Jull, Morley A. Poultry Husbandry. 2nd ed., 1938. McGraw-Hill.
- The Animal Welfare and Food Safety Issues Associated With the Forced Molting of Laying Birds (United Poultry Concerns)
- Induced Molting as a Management Tool (North Carolina State University)