Feeding Programs for Laying Hens: Molting Programs

Molting programs are designed to prolong the productive life of layers. It is commonly practised for egg type layers and turkey breeders, and is also being tried with broiler breeders in some areas. The aim of a molting program is not necessarily to induce a feather molt, but rather to shut down the reproductive system for a period of time. When birds resume laying, egg shell quality is improved, although egg size will also be increased. A number of molting programs have been used over the years involving feed withdrawal, diets low in sodium or calcium, or diets with high levels of zinc.

Feed/water withdrawal usually involves a prolonged molt period, whereas low sodium and calcium and high zinc diets have been tried as a means of inducing a short "pause" in lay, rather than a distinct molt. In general, these "pause" methods have not proven as reliable as the classical feed/water withdrawal. It is difficult to quantitate the economic advantage of a molting program. For example, if egg prices are high, then a short molt program may be beneficial, whereas with low egg prices, especially for large and extra large grades, there is no advantage to a very quick return to production. The criteria used in developing a molting program should be body weight and mortality. Mortality should not increase substantially during a molt and should not exceed 0.2% per day. If mortality is higher, then the duration and/ or degree of feed restriction should be reconsidered.

Perhaps the most important criterion is body weight. Ideally birds start their second laying cycle at the same weight as when they were juvenile pullets. This means that the degree of feed restriction must be sufficient to cause weight loss equivalent to that gained by the bird during the first cycle. In practice, this is often very difficult. For example, a flock of birds entering their first cycle at 1.3 kg may well be 1.4 kg entering their second cycle. In large part, this is the reason for increased egg size with second cycle birds. Weight loss should therefore be in proportion to bird weight gain during the first cycle. For flocks that are very heavy, more severe restriction is required, and vice versa. The time of initiation of a forced molt is also quite variable. In California, where most of the molting work has been pioneered by Dr. Don Bell, it is quite common to have two or three relatively short laying cycles - in this situation the first molt period may start at 60-65 weeks of age. More commonly, a molt will be initiated when layers are 75-80 weeks of age, when egg shell quality is a problem.

The main advantage of a molting program, is improved shell quality during the second and third laying cycles. The longer the molt period, within reason, the better the persistency of egg production and shell quality during a second or third cycle. For many situations therefore, the old saying of "short molt, short second cycle" holds true.

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