GOOD MOLTING PRACTICES IN COMMERCIAL LAYERS
Force molting is a practice that has been used by the commercial egg industry to rejuvenate flocks for extending laying cycle and restoration of egg quality. The main objective of force molting is to cease egg production of hens and that they enter a non-reproductive state. There are several force molting methods. Feed withdrawal has been widely used in recent years due to its easy application, economic benefits and agreeable post-molt performance. Forced molting, sometimes known as induced molting, is the practice by some poultry industries of artificially provoking a flock to molt simultaneously, typically by withdrawing food for 7–14 days and sometimes also withdrawing water for an extended period. Forced molting is usually implemented when egg-production is naturally decreasing toward the end of the first egg-laying phase. During the forced molt, the birds cease producing eggs for at least two weeks, which allows the bird’s reproductive tracts to regress and rejuvenate. After the molt, the hen’s egg production rate usually peaks slightly lower than the previous peak, but egg quality is improved. The purpose of forced molting is therefore to increase egg production, egg quality, and profitability of flocks in their second or subsequent laying phases.
However, groups for the animal rights have recently been pressing for an end to force molting by feed withdrawal, claiming that feed withdrawal is highly stressful to the hen. For this reason, researchers have examined alternative force molting methods to feed withdrawal. These methods included high dietary zinc supplementation, diets with low sodium contents, wheat middling, barley, cottonseed meats, and oat, which have been successfully used for induced molting. Brown-shelled eggs contain relatively large amounts of protoporphyrin-IX and relatively small amounts of biliverdin-IX. Eggshell color is determined by stress, disease and by the age of the hen. Egg quality is important for commercial egg producers. As the hen age increased, egg weight was increased while shell strength, shell thickness, albumen height and Haugh unit decreased. Hens can be molted to induce another egg cycle, which will improve egg quality.
There are several different methods of inducing artificial molting of laying hens. One of the most practical methods applied during the last two decades is based on restriction of feed. This method, in practice is very popular and usually gives successful results. The eggs produced during the second egg laying cycle usually have larger weight than those during the first cycle, the quality of the shell is always much better than during the last phase of the first egg laying cycle, egg laying intensity reaches 92-94% of the intensity during the first cycle and the feed conversion is about 10% higher.
Force molting is a management tool adopted by farmers to give the rest at the end of a long period of egg production and extend the productive life of flock to 110 weeks or longer. The practice of molting continued to increase and spread widely in the most of egg production countries of the world with the time as a tool to rejuvenate the spent hens. The decision of using a force molting program depends on several factors, such as: price of replacement new flock, egg quality, egg price, feed cost, maximum facility use and employed molting method. Methods conventionally used for induce molting in commercial layer can be classified in three main ways:
1.limination or limitation of food and/or water;
2.feeding the birds low nutrient rations deficient in protein, energy, calcium or sodium;
3. Administration of drugs, hormones, and metals including prolactin, chlormadinone, and progesterone; and high levels of iodine, dietary aluminum, and zinc, coincided with some variations and modifications, such as length of the treatment, lighting schedule and the age of molt.
The conventional feed withdrawal/deprivation (fasting) procedure is most widely used in poultry production because it is simple, practicable and economical technique that can be used in combination with light and/or water restriction. Fasting is the most frequently used method to induce molting due to its low cost and high efficiency. The increasing public awareness of the animal stress associated with feed withdrawal has led researchers to investigate alternative molting processes. Mineral induced molting programs are also adopted. The uses of higher levels of either aluminium salt or dietary zinc have been successfully practiced. Also, the use of low sodium diet was found to be an effective procedure for molt induction. It was observed that molt induction by feeding hens a diet containing high levels of zinc oxide or zinc acetate resulted in stoppage of egg production within 5 days. Several non-feed removal procedures were used to induce molting in hens. Ideally, a good molting method should: get the flock out of production within 5- 6 days, keep flock out of production until it has rested, bring it back into production when needed, simple to implement, low in cost, result low mortality and lead to high subsequence performance.
Molting is a natural seasonal event in which birds substantially reduce their feed intake, cease egg production, and replace their plumage. Induced molting is a process that simulates natural molting events. When birds return to full feed, a new plumage develops and the birds resume egg production at a higher rate with better egg quality. Induced molting extends the productive life of commercial chicken flocks and results in substantial reduction in the number of chickens needed to produce the nation’s egg supply. Induced molting also has a positive impact on the environment through reduction of waste and natural resources needed for growing more birds for egg production. However, molting induced by water deprivation or fasting causes discomfort and stress in hens.
Molting in avian species is generally defined as the periodic shedding and replacement of feathers. For most wild birds molting involves reproductive quiescence. Domestic hens experience a reduction in reproductive function during a naturally occurring molt, but it has been found to be an incomplete reduction in function. The hen often continues to lay eggs at a low rate for a prolonged period. This is a period of unprofitably low egg production for the commercial egg producer that, in the past, would have signified the end of the useful life of the flock. A decreasing price for eggs and meat products derived from spent flocks has generated interest in methods that allow flocks to be kept for more than one year. Causing the onset of a molt to occur at a time other than that of a natural molt completely halts reproductive function and precipitates a loss of feathers. A reduction in body fat and the regression of the female reproductive tract result in a significant loss of body weight. Egg production resumes and increases rapidly to a profitable rate following an induced molt. Traditional approaches to inducing a molt involved removing feed, water, or both from the hens and reducing the photoperiod to that of natural day length or less. Hens were fasted for a length of time sufficient to affect complete involution of the reproductive tract. Recently, more research has been done to evaluate methods other than feed removal for inducing a molt and non-feed withdrawal methods are now in common use.
Commercial hens usually begin laying eggs at 16–20 weeks of age, although production gradually declines soon after from approximately 25 weeks of age. This means that in many countries, by approximately 72 weeks of age, flocks are considered economically unviable and are slaughtered after approximately 12 months of egg production, although chickens will naturally live for 6 or more years. However, in some countries, rather than being slaughtered, the hens are force molted to re-invigorate egg-laying for a second, and sometimes subsequent, laying phase.
Forced molting simulates the natural process where chickens grow a new set of feathers in the Autumn, 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 was the norm, the Autumn molt caused a seasonal 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
The commercial induced molting procedure is generally carefully monitored and controlled. Current practices include reduction of photoperiod (day length) and dietary restrictions (including diets of low nutrient density) that result in cessation of egg production.
Fasting—Stress induced by fasting during molting programs leads to elevated concentrations of circulatory adrenal corticoids, which may cause an impaired immune response. In addition, feed withdrawal during an induced molt is detrimental to the skeletal integrity of hens. Research has shown that fasting is not necessary to induce a molt in laying hens. There are many effective non-fast methods that can be used to induce a molt including, but not limited to, feeding of low-sodium, high-zinc, high-corn5, high-wheat, oral thyroxine6, ad libitum alfalfa and low-calorie1 diets. Also, molting induced by feeding a non-fasting diet of wheat middlings and corn has been shown to be less deleterious to bone mineralization as compared to a fast-induced molt. Behavioral patterns of hens in various molting programs have been examined by Dunkley et al. Nonnutritive pecking behavior is characteristically associated with hens undergoing feed withdrawal. The researchers found that hens subjected to feed withdrawal displayed nearly twice as much nonnutritive pecking when compared to hens fed a diet of alfalfa combined with a layer ration or fully fed hens. Another study revealed that hens subjected to a fast-induced molt exhibited more cage pecking during the molting stage than prior to molting and that hens undergoing both fast- and non-fast induced molts were more aggressive with other cage mates during the molting stage than during the pre-molt stage. Results of vocalization studies further support that frustration is associated more with food deprivation than with low-calorie diets. A higher gakel-calling rate and changes in vocal acoustic structure were observed in hens subjected to a fast-induced molt, but not in hens subjected to a non-fast-induced molt or that were not molted.
Water deprivation results in higher mortality and morbidity during the early stages of the molt cycle. Water deprivation is not necessary to achieve a molt in poultry and is inhumane. Light conditioning prior to induction of a molt has been shown to eliminate the need to restrict water to effect cessation of lay.
The chick goes through one complete and three partial molts during its growth to point of lay, after which the mature bird normally undergoes one complete molt a year, usually in autumn although this depends on the time of the year at which the bird commenced laying. Generally complete molting occurs from 1-6 weeks and partial molting at 7-9 weeks, 12-16 weeks and 20-22 weeks, and during this latter molt the stiff tail feathers are grown.
The laying hen
Natural molting usually begins sometime during March-April and should be completed by July when egg production recommences. The three main factors which bring about molting are:
• physical exhaustion and fatigue
• completion of the laying cycle. Birds only lay eggs for a certain period of time
• reduction of day length, resulting in reduced feeding time, and consequent loss of bodyweight.
Eleven months continuous production is expected from pullets hatched in season, so that if a flock of pullets commenced laying in March at six months of age, they should continue laying until the following February, although the odd bird may molt after laying for a few weeks. These few birds however should begin laying again after June 22 (the shortest day of the year) and continue in production until the following autumn.
Pullets coming into lay in June should lay until the following April thereby giving eleven months continuous egg production without the aid of artificial light. Pullets coming into lay in spring (August) should lay well into April (9 months) but unless artificial lighting is provided, most of them will molt during May and June.
Molting and nutrition
Cessation of lay and molting indicate that the birds’ physical condition is deteriorating, and is therefore unable to support egg production, continued nourishment of their feathers and body maintenance. Feathers contain protein and are more easily grown when laying ceases, because of the bird’s difficulty in assimilating sufficient protein for both egg and feather production. During the molt the fowl still requires a considerable amount of good quality food to replace feathers and build up condition.
Good layers and molting
The time at which a laying hen ceases production and goes into her molt is a reliable guide as to whether or not she is a good egg producer. Poor producing hens molt early (November-December) and take a long time to complete the process and resume laying i.e. she will hang in the molt and be out of production for a long period – from six to seven months. Poor producers seldom cast more than a few feathers at a time and rarely show bare patches. High producing hens molt late, molt for a short period (no more than 12 weeks) and come back into production very quickly. Rapid molting is not only seen in the wing feathers of good producers, but also in the loss of body feathers generally. Because of this it is common to see a late and rapid molting hen practically devoid of feathers and showing many bare patches over her body.
The molting process
Molting takes place in a fairly definite order. Feathers are confined to definite tracts or areas of the body surface, with bare patches of skin between. The first plumage is lost from the head and neck, then from the saddle, breast and abdomen (body), then the wings and then from the tail.
While the first feathers are being dropped from the neck and body, good layers will often keep laying, but when the wing feathers begin to drop, laying usually ceases.
The main wing feathers consist of four tiny finger feathers on the extreme tip of the wing, then ten large primary or “flight” feathers, the small axial feather, and the fourteen secondary feathers, which are smaller and softer than the primaries.
When the wing molts, primary feathers are shed first, from the axial outwards to the end of the wing, and then the secondaries, which are not shed in such a set order as the primaries. The axial feather is dropped at the same time as the secondary next to it. The new quill starts to grow as soon as the old feather is out and takes approximately six to seven weeks to grow. The molt is complete when all primary flight feathers on the wing are replaced. The feathers of the molted bird are large and full, softer, cleaner, brighter and glossy in contrast to the feathers before molting which were small and hard, dry, frayed and tattered.
The molting process. Primary feathers are shed first from the axial feather outwards to the end of the wing. Number 1 primary feather is first to drop followed by a number 2 and then in order to number 10. While the primaries are being shed the secondaries begin to drop but not in any set order
The difference between a rapid and slow molter is not due to a difference in growth rate of the individual feather, but because the rapid molter renews a large number of feathers at the same time. With this knowledge, the rate of molting can be ascertained by examining the number of flight feathers on the wing being replaced simultaneously. If a hen is found to have grown some of her primaries before starting to molt her secondaries, it may be assumed that she laid well into the molt and was therefore a good layer.
Sometimes, high producing hens do not molt all their primary feathers but carry them on for another year. Generally, a layer molts when production ceases although if the bird has an inherited tendency for high production, molting will probably precede cessation of production, and conversely if she is a poor producer. Modern laying breeds should molt in late autumn because they have been bred specifically for egg production i.e. to lay at a higher rate and for a longer period of time.
Vacation molts, neck molts or partial molts
Old feathers are usually retained by a laying bird which lays regularly. Should she cease production for any other reason than for mild sickness or broodiness she will lose her feathers.
If a hen ceases production during spring or summer, she may molt one or two primaries, then stop molting and come into lay again. This is known as a vacation molt. When she starts her full molt later in the autumn, she will drop the next feather in sequence and molt in order of the remaining primaries. A neck or partial molt is sometimes experienced by a bird without any loss of production, but if the molting extends beyond the neck molt stage the hen ceases production.
The presence of “pin” feathers (new emerging feathers) usually indicates a short or partial molt.
Some birds molt continuously and can be easily detected in the flock by the spotless condition of their new feathers. These birds are poor producers and should be culled.
Stress factors and molting
Natural molts can occur any time of the year due to birds being subjected to stress. A bird is stressed when the environment or management present a challenge to which the bird cannot respond without suffering a harmful effect. A hen subjected to a mild stress condition in late spring when in full production will suffer a drop in egg production whereas the same stress condition applied to a bird in the autumn will cause her to cease laying and molt.
The following are common stress factors which can induce molting:
• decreasing daylight
• decreasing artificial light
• Loss of bodyweight
• Internal parasites
• excessive cold
• heat waves
• Feed, feeding and feedstuffs
• deficiencies of essential ingredients
• irregular feeding
• insufficient feed
• Predators e.g., cats and dogs
• Fright – wild birds and children
• Peck order – low vitality
• Prolonged broodiness
• Mismanagement: overcrowding, movement to another house, water deprivation, insufficient feed and water space, faulty ventilation, wet litter, debeaking, vaccinations, exposed housing, etc.
Force molting is a practice adopted by some commercial egg producers to bring about a rapid molt so that all the birds come back into lay for a second time at a certain time of the year, usually in autumn. It is achieved by subjecting a flock to a programmed combination of mild environmental stress factors causing the birds to cease laying and consequently molt e.g., decreasing the artificial lighting program. Force molting is a practice not normally applicable to the household situation. Natural molting is slower and more erratic than force molting.
Production and molting
After molting, the second year of egg production will be between 10 and 30% less than that achieved by the birds in their first year of lay. This is because the rate of lay is lower and the birds cease to lay earlier in the following autumn. Birds which have molted twice and are laying for their third year will lay only 70 to 80% of their second years eggs i.e., about 60% of their first year’s production.
Like hens, cockerels also molt, and while in this condition are nearly always infertile due to loss of bodyweight and because their reproductive physiology is undergoing a resting phase. Care must be taken to ensure that cockerels do not lose more than 25% of their bodyweight while molting as this can lead to sterility.
Advantages and disadvantages
The advantages of keeping hens during the molt and the following year is fourfold:
• it is cheaper to carry a bird through a molt than to buy replacement pullets
• fewer replacement pullets may be needed, and buying can often be deferred, which can mean a saving of money, time and transport
• molted birds are hardier, and not as prone to disease
• if strict culling is carried out during the first year, only high producing, efficient birds will be retained.
The main disadvantage is that although molted birds eat less feed than pullets, they also lay less eggs. Overall, their conversion of feed into eggs, and feed cost per dozen eggs is higher.
Other disadvantages are:
• during the molt the birds continue to eat but remain unproductive
• if the birds are to be slaughtered for the table after two years of laying they will not be as tender to eat
• too few birds may be retained to provide sufficient eggs the following year.
Year-round laying and molting
All-year-round egg production can be achieved by purchasing pullets at point-of-lay in the autumn to provide sufficient eggs while the older birds are molting. When the rate of lay of the pullets declines in the summer, the additional eggs from the molted birds should sustain an adequate supply. The following autumn the older birds can be killed for the table, the best pullets allowed to molt and another lot of pullets on point-of-lay purchased. In effect therefore, allowing for 20% wastage of pullets due to deaths and culling, only 70% of the normal pullet requirements need to be purchased, and at the same time a relatively constant year-round supply of eggs is guaranteed.