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Molting Layers—Alternative Methods and Their Effectiveness

K. W. Koelkebeck^*,1 and K. E. Anderson

^* Department of Animal Sciences, University of Illinois, Urbana 61801; and Department of Poultry Science, North Carolina State University, Raleigh 27695

¹ Corresponding author: kkoelkeb{at}uiuc.edu

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION REFERENCES

 
The molting of commercial layers has been under increased scrutiny by animal rights groups, who have said that this practice is highly stressful and one which negatively affects the welfare of the hen due to the initial period of fasting that has been used to stop egg production. In recent years, there has been a recognized need to develop practical alternatives to molting layers other than the use of fasting. Thus, the University of Illinois, University of Nebraska, North Carolina State University, and the University of California have all researched this area. In all of these studies, the methods involved comparing a normal fasting method (i.e., 5 to 13 d), to feeding low-energy and protein diets using ingredients such as wheat middlings, soybean hulls, and corn or diets with graded levels of added salt and without salt (University of Nebraska, University of California). The molt period (28 d) included full-feeding of these diets. In these studies, postmolt production performance for the nonfeed withdrawal techniques was comparable to the fasting method. Several researchers have also evaluated the behavioral repertoire of laying hens, which includes feeding, drinking, comfort, social, reproductive, and anti-predator behaviors. In addition, related behaviors such as aggression, escape-avoidance, and submission have been of particular interest as potential indicators of welfare during molting. In these studies, genetic selection, strain, density, or molt program do not appear to adversely influence the behavioral patterns during the molt. The behavior patterns displayed during a molt program appear consistent with the response to physiological changes that layers experience and do not appear to compromise the welfare status of the hens. Appetitive behaviors were not affected by strain but were affected by production phase and molting. Strain or production phase did not influence the frequency of aggressive and submissive acts. Thus, the use of alternative nonfeed withdrawal molting methods provide comparable laying hen well-being and may enhance the transition from a productive to a resting state.

Key Words: molting • laying hen • behavior

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION REFERENCES

 
Molting is a major event in the annual life cycle of most avian species, both wild and domestic. In laying hens, this type of research has been ongoing for more than 100 yr (Rice, 1904; Rice et al., 1908; King and Trollope, 1934; Frasier, 1948; Swanson and Bell, 1974a,b,c,d; Brake and Carey, 1983; Davis et al., 2000; Anderson et al., 2004; Biggs et al., 2004). Stevens (1996) commented, "There are times when birds in the wild do not eat in spite of having food readily available, e.g. during moulting, breeding, and egg incubation." (p. 96). This quote indicates the importance birds place upon seasonal breeding and other activities. Stevens (1996) indicated that fasting is especially pronounced in geese that may be anorexic for 2.5 mo and king penguins that fast for 4 to 6 mo. During a molting event, the metabolic rate and protein synthesis increases, along with a loss of adipose tissue, bone mass, and humoral immune system suppression (Kuenzel, 2003; Mumma et al., 2006). Molting also results in an alteration of the hormonal system of the hen (Swanson and Bell, 1974a,b,c,d; Davis et al., 2000). Hormonal changes are typically associated with molting and broodiness in the wild, seasonal changes resulting in limited food supply, and the husbandry practice of molting in the commercial egg and breeder industries. The hen is capable of coping with and compensating for changing conditions in its environment to maintain physiological homeostasis (Clarenburg, 1986; Freeman, 1987). The hen responds by using physical, chemical, anatomical, and physiological mechanisms at its disposal to maintain this status. The hen has functions that are constitutive or always functioning and others that are adaptive, i.e., come into being as the need arises to maintain the homeostatic state. The following are some of the physiological mechanisms, both constitutive and adaptive, to limited or total restriction of food that occur postprandial, between meals, and during a fast, and it is arbitrary in determining at which point one starts and the other begins (Clarenburg, 1986). The metabolism of the chicken readily moves between these processes throughout the course of a regular day. Upon prolonged abstention of food, other essential nutrients are used up, for example, vitamins, minerals, essential amino and fatty acids, lipotropic factors, and carbohydrates, which can create a life-threatening situation. Starvation triggers a collapse of homeostasis, the basal metabolic rate declines, and simultaneously the body economizes on all energy expenditures to extend the survival of the animal; however, this response does not occur in the molting programs associated with poultry husbandry practices. This indicates that molting, regardless of the stimulus used to initiate, is more than just the replacement of the feather coat as shown in numerous studies. Molting in the domestic avian species is associated with the limiting of nutrient intake of all or selected nutrients by choice or as a commercial husbandry practice or by altering the hormonal balance in the laying hen.

In recent years, the traditional method of molting laying hens by feed withdrawal has been under scrutiny by animal rights groups and others who claim that this practice is highly stressful to the hen. Thus, it was about 6 yr ago that the United Egg Producers (UEP; Alpharetta, GA) decided to fund research in this area. At the same time, food companies such as McDonalds, Burger King, and Wendy’s International told egg producers that they could sell them eggs only if they came from flocks that were not molted. Because the practice of molting laying hens is of an economic advantage to most companies, the UEP decided to fund research on developing nonfeed withdrawal molting programs that could be used in the commercial industry. Therefore, development of viable and economical methods of induced molting without feed withdrawal began. Thus, this paper discusses the molting programs developed by 5 universities and then focuses on the behavioral responses of hens subjected to feed withdrawal and nonfeed withdrawal methods.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION REFERENCES

 
The 5 universities that were commissioned by the UEP to conduct experiments on induced molting of laying hens by nonfeed withdrawal were as follows: University of Nebraska, University of California-Davis, University of Arkansas (Fayetteville), University of Illinois, and North Carolina State University. Research on nonfeed withdrawal molting programs at the University of Nebraska (Lincoln) revolved around the feeding of "nutrient balanced" diets (2,684 ME of kcal/kg, 10 and 12.5% protein, 1 and 1.5% Ca, and 0.5% available P; Scheideler and Beck, 2002). For the 2 nonfast molt diets recommended, salt would not be added to the diets. Additionally, the recommendation for lighting was to provide 16 or 24 h of light during the week before the beginning of the molt period. At the start of the molt, the lights would be reduced to 8 h/d, then 10 h/d at wk 4, then increased 1 h/wk until a 16-h photoperiod was obtained.

Research at the University of California-Davis examined traditional and nonfeed withdrawal molting methods in 5 field tests (Bell and Kuney, 2004). Paired houses were used on 3 California commercial egg farms. The nonfeed withdrawal molting methods utilized diets with low levels of Na, Ca, and protein. For the 3 farms tested, 2 to 4 identical houses per comparison (1 or 2 treatment houses vs. 1 or 2 control houses), sister birds (same hatch date, strain, and raised together), 5 strains (1 farm used 2 sets of houses for 2 strains, and 1 farm repeated the first test with a second strain in a new set of housing), and a total of 440,000 hens in the 5 tests. Each flock was from 66 to 70 wk of age at the start and was kept for 37 to 38 wk of second-cycle production. Molt treatments consisted of control houses that were fasted for varying lengths of time, followed by limit feeding to 28 d or a nonfasted treatment fed a low-nutrient diet for the molt period (4 wk). The nonfasted treatment consisted of a no-added-salt diet (Na 0.02%), low Ca (0.83%), and low protein (7.8%).

Research at the University of Arkansas has taken a different approach than using conventional feedstuffs in a nonfeed withdrawal molting program. Their work has examined the effects of supplementing molt diets with iodinated thyroxine. In one of their published reports, hens were fed different levels of thyroxine from several sources, and the performance results were compared with a conventional feed withdrawal method (Bass et al., 2006). This research has been done in a more laboratory-like setting, and work is continuing on developing a patent for this method used.

Research conducted at the University of Illinois has involved the use of several nonfeed withdrawal molting techniques compared with a conventional feed withdrawal molting method in 5 experiments over the past 5 yr. These studies have included nonfeed withdrawal diets such as corn, wheat middlings, soybean hulls, corn gluten meal, dried distillers grains with solubles, and mixtures of corn and the other ingredient combinations. This was done in order for the diet to flow reasonably well in a commercial feeding system. The energy and protein combinations that have been tested have all been on the low side, and the performance results that have been obtained are a result of the low energy levels of these diets. In addition, the reason as to why this approach was taken was to develop nonfeed withdrawal molt diets that utilized ingredients that were cost-effective and relatively easy for a producer to obtain. In a recent report by Koelkebeck et al. (2006), long-term performance results (40 wk) were shown for nonfeed withdrawal molting programs utilizing feed ingredients such as corn, wheat middlings, and soybean hulls and combinations of corn and wheat middlings and soybean hulls were reported. As in the studies by Bell and Kuney (2004), the molt diets were fed for a 28-d molt period, with the daily photoperiod being reduced as well. In several studies, they reported that some diets were feed-restricted to force the hens to go out of egg production during the molt period. They also reported that a combination of corn and soybean hulls and corn and wheat middlings seemed to provide the best postmolt performance.

In the work done at North Carolina State University, 4 molt programs were examined (Anderson, 2002a). In the first program, hens were not molted. In the second program, hens were fed a nonfeed withdrawal molt diet consisting of a low-protein (9.8%), low-energy (1,650 kcal/kg of ME) diet. In the third program, hens were fasted for 5 d then fed diet number 2. In the last program, hens were fasted for 13 d then fed a resting diet (16% protein, 2,866 kcal/kg of ME) to 28 d. In this work, water was available at all times, and the daily photoperiod was reduced as well. Performance parameters and behavioral measurements were recorded premolt, during the initiation of the molt, resting portion, and for 35 to 40 wk after the molt period.

	RESULTS AND DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION REFERENCES

 
Production
The research conducted at the 5 universities indicated that molting laying hens with a nonfeed withdrawal method is feasible. At the University of Nebraska, their research showed that the level of Na in the diets did not affect feed intake; however, the cessation of lay and BW loss were not as complete as those for hens molted by a 8- to 10-d fasting method. In addition, they reported that fasted birds had better eggshell quality in the late postmolt production period. But, postmolt production of hens molted by a nonfeed withdrawal method was comparable to those that were fasted. In the University of California research, egg production and BW losses differed between traditional molted flocks vs. those fed diets with low Na levels during the first 4 wk, but after that, performance was similar. In addition, mixed economic results were noted between both methods. In the University of Illinois research, postmolt production results were shown to be similar between hens that were fasted vs. hens fed various nonfeed withdrawal molt diets. In all studies done to date, it was shown that 0% egg production could not be obtained by molting hens with any nonfeed withdrawal diets that were tested vs. using a fasting program. However, long-term postmolt performance was similar for hens fed molt diets such as corn:soybean hulls (47%:47%) or corn:wheat middlings diets (23%:71%) compared with a 10-d fed withdrawal program. Their results also showed that no differences in mortality or postmolt egg weight, egg-specific gravity, or feed efficiency occurred between the 2 molting methods. Finally, the results obtained at North Carolina State University indicated that using a low-protein, low-energy molt diet without fasting provided for good post-molt production results. Furthermore, the nonfasting method resulted in comparable egg income and feed costs compared with the fasting methods. Thus, research data obtained at these universities indicated that a non-feed withdrawal molting method can be used in the industry with success, and, furthermore, this method of molting laying hens does not seem to compromise the welfare of the hens based on performance results.

Behavior
The establishment of behavior patterns in evaluating changes in behavior due to a management practice is a good means of evaluating the overall effect of management on a hen. However, if behaviors are taken out of context, there could be a negative aspect of behavior that is exacerbated, when in fact there may be a compensating behavior that would mitigate its effect. The 3 general classes of behaviors that can be used are acts independent of conspecifics, appetitive behaviors, and social behaviors. Acts independent of conspecifics are behavioral acts that the hens could perform independently of cage mates. Appetitive behaviors are those that involve the consumption of food and water or seeking for food. Social behaviors involve the interaction of 2 hens either within the cage or between cages. These behaviors are typically defined as aggression or social dominance but may also constitute some social grooming behaviors. There are a number of other behaviors described by Hurnik et al. (1995), but the ability to differentiate all of these during real-time observations becomes untenable.

It has been established that the behavior of laying hens changes rapidly as they settle into a new cage environment (Anderson et al., 1989). After the hens settle in to the housing environment, their behavior patterns also change as the hens progress through the different phases of a 2-yr production period including molting (Anderson et al., 2004). Concern has been placed on the behavior changes that result from the transitions from first cycle to the molting period that has consisted of a fast and postfast phase, then back to a productive state in the second cycle. These behavior changes associated with molting appear to be predominantly adaptive changes, as would be expected as the hens progress through significant physiological changes moving into a nonproductive period with limited feed and nutrient access (Webster, 2000; Anderson et al., 2004). Webster (2000) and Anderson et al. (2004) found that during the molt, the acts independent of conspecifics behaviors shifted to those requiring lower energy expenditures. The appetitive behaviors shifted from feeding to pecking inedible objects, which is related to food-seeking behaviors. Then immediately postmolt, preening increased during the period when feather growth would be expected to progress at a high rate.

Aggression has been shown to change as the hens progress through the different production phases, which could be interpreted as negative. It has been shown that the number of aggressive acts declines significantly during a molt induced by fasting (Anderson et al., 2004; Biggs et al., 2004). However, alternative nonfasting methods have been shown to increase total aggression by 8 times over the hens that were not molted; this corresponds with increases in submissive and avoid and escape behaviors (Anderson, 2002b; Biggs et al., 2004). Anderson et al. (2004) found that aggression levels were no different between the first- and second-cycle phases. These observations indicate that fasting does not increase aggression; in fact, the hens in the feed-restricted molt group had the lowest levels of aggression. There are increases in submissive and avoid and escape behaviors corresponding with increased aggression; these increases may be the coping mechanism of the subordinate hens. This behavioral increase suggests that subordinate hens are capable of removing themselves from the aggressor or showing submissive behavior to avoid an aggressive act. The higher level of aggression as compared with the subordinate acts may indicate that the social structure within the cages may be made up of significant pairings of equally dominant hens that initiate and receive the predominant interactions. This may also be a result of increased skin sensitivity due to the start of feather push-out, which begins 8 to 11 d after the initiation of a molt as suggested by Webster (2000). It has been shown that the highest levels of aggression were actually in the nonfasted molt group who also had the highest heterophil:lymphocyte, indicating increased stress levels.

Aggressive behavior appears to be significantly influenced by the individual layer strain (Anderson et al., 2004). This was supported by a second study by Anderson (2002b) that indicated aggression levels were different among white egg-laying strains during the initiation of a molt program and during the resting portion of the molt period.

It has been stated that molting is a stress on the hen that results in cessation of egg production and a significant loss in BW. This is a true statement, as is shown by the research of Davis et al. (2000). He showed that the heterophil:lymphocyte ratio and corticosterone were elevated during the molt period. However, he indicated that these levels were not significantly different from the levels observed during peak egg production. Stress is the initiator of the molt in this commercial setting, as it is in the wild. The question arises as to the humaneness of this act. This study showed that if one looks at the molt period out of context, then, yes, it might have the appearance of inhumane. However, when molting is examined within the context of a total production period, the viewpoint changes. We must remember that the absence of stress is death (Selye, 1973) and that there are 2 types of stress, eustress (good) and distress (bad). Based upon these reviews and research, it would be difficult to support the supposition that the hens are under distress during a molt. The changes in behavior patterns and fearfulness do not indicate distressful conditions, which are outside the range of normality. This holds true be it for behavior, production patterns, or physiology, as described by Clarenburg (1986). Hens move through adaptive phases in their life on a continuous basis, regardless of how they are housed or what husbandry practices are imposed.

From the outside looking in, the practice of induced molting appears to be cruel, with the imposed fast or, for that matter, imposed nutrient restrictions, as in the maintenance diet used herein. However, the benefits to the total population are apparent and can be well documented. Anderson (2002a) found that, overall, the molting of laying hens improved the livability of the flock by as much as 9% in some white egg strains. Molting also resulted in improved reproductive efficiency and egg quality. This indicates improved health and vitality as compared with hens that had never been molted. The practice of molting, which has been examined and researched for almost 100 yr beginning with Rice (1904), has never been used to willfully inflict harm or injury on the laying hen. To the contrary, these practices were developed to ensure the reproductive capacity and health of the hen.

Received for publication November 30, 2006. Accepted for publication December 2, 2006.

	REFERENCES

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