Forced Molting

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.