Changes in immune and hematopoietic system during an induced moult

Berry (Reference BERRY2003) and others have provided comprehensive reviews of induced moulting. During moult, the proportion of CT 4 lymphocytes decreased while the proportion of CT 8 lymphocytes increased (Holt, Reference HOLT1992), suggesting immuno-suppression. Antibody levels did not appear to change even though a decrease in the number of B cells was observed in laying hens. These changes were similar to those observed in birds in stressful conditions and trauma. Moulting birds failed to respond to new antigenic challenges. Reportedly, the lack of response contributed to the increase in incidence of Salmonella enteritidis (SE) during moult (Porter and Holt, 1993; Holt et al., Reference HOLT, BUHR, CUNNINGHAM and PORTER1994). Moreover, other changes such as haemoconcentration (packed cell volume) and the involution of the ovary and oviduct occurred. As ovarian function returned, red blood cells declined. An increase in oestrogen caused expansion of vascular volume and haemodilution. Other results showed that induced moulting involved many physiological changes in immune function and lymphoid structure, reproductive tissue, and the endocrine system (Berry, Reference BERRY2003).

Gastrointestinal system and shell development during post moult

Upon the reintroduction of feed, duodenal weight, which decreased during induced moulting, regained its original size. In addition, the intestinal Ca binding protein concentration increased post-moult as compared to that for unmoulted hens (Berry and Brake, Reference BERRY and BRAKE1991). Vitamin D (1,25 dihydroxycholecalciferol [1,25(OH)₂D₃]), in combination with oestrogen, bound the Ca-binding protein in the intestine and shell gland. As hens aged, plasma concentrations of 1,25(OH)₂D₃ decreased during moult (Abe et al., Reference ABE, HORIKAWA, MATSUMURA, SUGUHARA, KUBOTA and SUDA1982). When egg production returned during post-moult, plasma 1,25(OH)₂D₃ was restored to levels reported in young laying hens (Abe et al., Reference ABE, HORIKAWA, MATSUMURA, SUGUHARA, KUBOTA and SUDA1982) and its receptors in the shell gland were increased (Berry and Brake, Reference BERRY and BRAKE1986). Cellular proliferation of receptors in the shell gland, correlated with increased tissue receptivity to 1,25(OH)₂D₃ and Ca binding protein content, elevated level of the hormone, and heightened tissue sensitivity (Heryanto et al., Reference HERYANTO, YOSHIMURA and TAMURA1997).

Endocrine system and removal of feathers

Decuypere and Verheyen (Reference DECUYPERE and VERHEYEN1986) reported that renewal of feathers was caused by a general antagonism between the pituitary-thyroid and pituitary-ovarian axis during cessation of lay. When hens moult, there is elevated thyroxin, followed by elevated tri-iodothyronine and deceleration of oestrogen release which results in suppression of feather papillae activity (Berry, Reference BERRY2003). After the moult, thyroxin or progesterone activated the feather papillae. Ultimately, a newly formed feather expelled its predecessor. The quantity of corticosterone depended on the method used to induce moulting. Feed deprivation caused a rapid, complete moult, associated with heightened corticosterone levels, related to inhibition of the hypothalamic-pituitary-gonadal (HPG) axis (Williams et al., Reference WILLIAMS, ETCHES and RZASA1985). The deprivation made the pituitary refractory to gonadotropin releasing hormone, leading to less luteinizing and follicle stimulating hormone (Wilson and Cunningham, Reference WILSON and CUNNINGHAM1980). Prolactin affected involution of the ovary, subsequent reduction of ovarian steroidogenesis, and regression of the oviduct with the result of broodiness. In the jungle fowl and the domestic turkey hen, the endocrine changes accompanying moult induction commenced with rising prolactin levels. Eventually, this inhibited the HPG axis. However, in the commercially fasted laying hen, prolactin concentration increased only slightly or not at all (Scanes et al., Reference SCANES, SHARP, HARVEY, GODDEN, CHADWICK and NEWCOMER1979; Berry, Reference BERRY2003).

Moulting by feed withdrawal

Commercial layer flocks produce eggs for approximately twelve months and then become less productive towards the end of the laying cycle, which reduces net farm income (Koelkebeck et al., Reference KOELKEBECK, PARSONS, LEEPER. R.W. and WANG1993; Yousaf, Reference YOUSAF1998). At this time, producers can opt to slaughter the old hens and bring in a new flock of pullets, however the cost to raise the pullets, while receiving no income, and disposal of the previous flock are critical economical issues. Early in the 20th century, the concept of induced moulting by feed deprivation arose as a solution to these challenges (Holt, Reference HOLT1999). The efficiency of feed removal programmes in enhancing post moult productivity and economical feasibility insured a gain in popularity by the 1930's (Bell, Reference BELL2003). Most of the egg producers in California adopted induced moulting by feed withdrawal in the 1950's (Bell, Reference BELL2003). With induced moulting by feed removal, flocks laid for an additional year, thereby spreading fixed costs over a longer time and over more units of production. In 2003, more than 75% of all flocks were moulted in the U.S. (Holt, Reference HOLT2003).

Moult programmes

Conventional induced moulting usually involves removing feed, water, or both from the hens along with a reduction in the photoperiod. Hens were then fasted for a length of time sufficient to affect complete involution of the reproductive tract. According to Bell and Weaver (Reference BELL and WEAVER2002), prominent feed withdrawal moult programmes included one of the following:

• A single moult and two egg production cycles. Hens were moulted after about 10 months of egg production, allowed to produce for another cycle, and sold between 100 and 110 weeks of age.

• Multiple moult (two or more) moults and multiple egg production cycles. Hens were first moulted after 9 months of production, then held through successively shorter cycles and sold at 30 or more months of age.

A strong case for forced moulting

The concept of induced moulting by feed deprivation arose as a solution to disposal of old flocks with inadequate egg quality, low meat yields, brittle bones, and subsequent reluctance of processors to process old layer flocks (Holt, Reference HOLT1999). Additionally, the efficiency of feed removal programmes in enhancing post-moult productivity and economical feasibility ensured their popularity.

Moulting and stress

Webster (Reference WEBSTER1995) found that during feed withdrawal, cage pecking increased by a factor of three whereas feather pecking increased by a factor of eight. Early in the period of feed withdrawal (second day), frequent standing, head movement, displacement preening, and increased feeder related activity was observed as a consequence of conflict or frustration. Additionally, non-nutritive pecking of structural features (walls, cage wire, and floor) in the environment was observed. After hens learned to perform an operant behaviour to obtain delivery of feed, they produced gackel calls when denied access (Zimmerman and Van Hoof, Reference ZIMMERMAN and VAN HOOF2000). The number of calls increased in accordance with the length of time the hens had been deprived of feed (a maximum of 47 hours). Other reports noted that during the first three days of feed withdrawal, failed attempts at feeding resulted in temporary frustration, expressed by aggressive behaviour that resulted in stereotype pecking at objects like feeders (Duncan and Wood-Gush, Reference DUNCAN and WOOD-GUSH1971; Hocking et al., Reference HOCKING, MAXWELL and MITCHELL1996; Webster, Reference WEBSTER2000). Some hens pecked feathers of other birds as a displacement behaviour (Webster, Reference WEBSTER2000) and possibly a sign of sulphur amino acid deficiency (Mireles, Reference MIRELES2009).

As a moderate period of food deprivation (10-14 day) becomes stressful, a classical physiological stress response occurs (Mench, Reference MENCH1992). Observations in one study showed that from day of the moult, sluggish behaviour was recorded due to a decline in metabolic demand because of decreasing egg production and debilitation (Duncan and Wood-Gush, Reference DUNCAN and WOOD-GUSH1971; Reference DUNCAN and WOOD-GUSH1972).

Effect on human health

Research from the early 1990's to the present has amassed information about S. enteritidis in moulting hens (Holt, Reference HOLT1992; Holt and Porter 1992 a, b; Thiagarajan et al., Reference THIAGARAJAN, SAEED and ASEM1994; Holt et al., Reference HOLT, BUHR, CUNNINGHAM and PORTER1994; Holt, Reference HOLT1995; Holt et al., Reference HOLT, MACRI and PORTER1995; Holt et al., Reference HOLT, MITCHELL and GAST1998; Holt, Reference HOLT1999; Holt, Reference HOLT2003; Moore and Holt, Reference MOORE and HOLT2006). In total, results showed that S. enteritidis localised in the crop micro-environment and multiplied to spread rapidly throughout the intestinal tract. Moulting encouraged tissue invasion by S. enteritidis within 48 hours; S. enteritidis was recovered from the liver, spleen, and ovary. Marked histological inflammation was observed in the caeca and colon. Moulted birds with impaired immunity became readily susceptible to even fewer numbers of bacteria. High rates of intestinal shedding through faeces resulted in contamination of eggs, consequently threatening health of humans.

Increased incidence of infection was noted in moulting healthy birds not only through contaminated feed and feather consumption but through air or direct contact due to alterations in pathogenesis. Moreover, rodents exacerbated the disease conditions in layer houses. By five weeks post-moult, eggs contained the highest S. enteritidis population that declined by 6-10 weeks and dissipated to that of non-moulted hens by 11-20 weeks. An increased incidence of S. enteritidis reoccurrence was observed.

Other effects

In addition to S. enteritidis, adverse effects on other systems such as a decline in mineralisation of the medullary tibia and the humerus were reported (Mazzuco and Hester, Reference MAZZUCO and HESTER2005). An effect on the haemopoeitic system caused reduced vascular volume. The increase in packed cell volume led to haemoconcentration, causing further health complications (Mazzuco and Hester, Reference MAZZUCO and HESTER2005). Duncan and Mench (Reference DUNCAN and MENCH2000) reported that after the first laying cycle, hens became photorefractory (did not respond to long day lengths). These investigators also reported Ca depleted bones, resulting in reduced shell quality; overall exhaustion was noted. Moreover, induced moulting increased mortality compared to non-moulted hens (Duncan and Mench, Reference DUNCAN and MENCH2000; Hassanabadi and Kermanshahi, Reference HASSANABADI and KERMANSHAHI2007).

Organizational opposition

The challenges of induced moulting were observed by United Poultry Concerns (UPC) in 1992; articles published in Feedstuffs magazine in 1992 and 1993 highlighted these challenges (UPC, 2003; Davis, Reference DAVIS2005). During the same period in the UK and Europe, egg producers and poultry scientists were reluctant to stop conventional moulting due to profitability of high quality egg production during post moult. However, induced moulting was strictly banned due to hen welfare and food safety concerns (DEFRA, 1994). UPC, in conjunction with the Association of Veterinarians for Animal Rights (AVAR), held their first news conference in January, 1999, at the Poultry Exposition in Atlanta, Georgia to advocate a ban on the conventional practise (New Scientist, 1999). According to the UPC, their initiative received a tremendous response when thousands of letters and signed petitions opposing induced moulting were generated (UPC, 2005). Meanwhile, media such as the Washington Post, Poultry Press, New Scientist, and Feedstuff reported various views on moulting by feed withdrawal (Poultry Press, Reference POULTRY PRESS1999; Kaufman, Reference KAUFMAN2000).

Reports from the USDA Food Safety and Inspection Service (FSIS) in 1998 and the General Accounting Office Report on Food Safety acknowledged public health concerns associated with moulting by feed withdrawal (USDA, Reference USDA1995; GAO, 1999). The United States Department of Agriculture - Animal and Plant Health Inspection Service SE Pilot Project also supported results from studies of Holt and other scientists. According to the USDA, a ban on forced moulting at the time would save 29,400 people from infection with S. enteridits, accounting for 2.1% of all S. enteritidis cases every year (Jonas, Reference JONAS2004).

After five consecutive years of denying support of petitions against forced moulting, the American Veterinary Medical Association (AVMA) supported non feed removal moulting in 2004 (JAVMA News, Reference JAVMA NEWS2003; Fiala, Reference FIALA2004; PETA, 2004b). Petitions to the USDA and the Food and Drug Administration were filed by various concerned scientist and citizens (Duncan, Reference DUNCAN2000; Cunningham, Reference CUNNINGHAM2004; PETA, 2004 a, b). McDonalds^©, Burger King^©, and Wendy's International refused eggs from hens moulted by feed removal (Davis, Reference DAVIS2004). Moreover, top consumer groups, including the Centre for Science in the Public Interest, Consumers Union, and Public Citizen, supported discontinuation of the practise (Davis, Reference DAVIS2004).

With endorsement from the USDA and the American Humane Association, the United Egg Producers (UEP) Scientific Advisory Committee, having dealt with the issue of feed withdrawal for moulting since the early 1990's, amended the Animal Husbandry Guidelines for U.S. Egg Laying Flocks to specify the use of non feed withdrawal moult methods after January 1, 2006 (UEP, 2000; UEP, 2008). Furthermore, moulting hens would have to be fed nutritionally adequate and palatable food suitable for non-egg producing hens (UEP, 2000).

Use of low density diets

In order to obtain comparable results to those of feed withdrawal, alternative methods of non feed removal were suggested. Most diets contained varying levels of minerals, drugs or hormones and proteins from seed or agricultural by-products were tested (Bell and Kuney, Reference BELL and KUNEY2004). Although metals or hormones were efficient moult inducers, results of studies showed that they had disadvantages of residual effects and physiological alterations (Bell and Kuney, Reference BELL and KUNEY2004). Alternatively, results from studies on low nutrient density feed ingredients demonstrated promising outcomes (Whitehead and Shannon, Reference WHITEHEAD and SHANNON1974; Begin and Johnson, Reference BEGIN and JOHNSON1976; Nesbeth et al., 1976 a, b; Creger and Scott, Reference CREGER and SCOTT1977; Griminger, Reference GRIMINGER1977; Monsi and Enos, Reference MONSI and ENOS1977; Shippee et al., Reference SHIPPEE, STAKE, KOEHN, LAMBERT and SIMMONS III1979; Ross and Herrick, Reference ROSS and HERRICK1981; Gibson et al., Reference GIBSON, JACKSON and STEVENSON1982; Naber et al., Reference NABER, LATSHAW and MARSH1984; McCormick and Cunningham, Reference MCCORMICK and CUNNINGHAM1984. 1987; Hussein et al., Reference HUSSEIN, CANTOR and JOHNSON1988, Reference HUSSEIN, CANTOR and JOHNSON1989; Hussein, Reference HUSSEIN1996). Some comparative results are shown in Table 1.

High fibre agricultural products and by-products have been investigated for their usefulness in non feed removal diets as well. Although delay in return to production was noted, a 10% guar meal diet demonstrated equivalent performance when compared to a feed withdrawal moult (Patel and McGinnis, Reference PATEL and MCGINNIS1981). Similar results, along with an advantageous resistance to SE, were obtained by Gutierrez et al. (Reference GUTIERREZ, ZHANG, CALDWELL, CAREY, CARTWRIGHT and BAILEY2008) with 20% guar meal.

A diet containing grape pomace was found to be as efficient as feed withdrawal (Table 2). Moreover, it was beneficial due to its low cost. An increase in the percentage of grape pomace resulted in numerically higher mortality (McKeen, Reference MCKEEN1984). Contrary to UEP guideline, feeding grape pomace with thyroxin after one day of feed withdrawal was proposed as an alternative moult method (Keshavarz and Quimby, Reference KESHAVARZ and QUIMBY2002).

Vermaut et al. (Reference VERMAUT, DE CONINCK and ONAGBESAN1998) demonstrated that jojoba meal, a by-product from the extraction of oil from jojoba seeds, was an ideal low cost local feed source with no adverse effects (Table 2). Though jojoba is toxic to growing hens - hampering their ovarian growth - 12% of high protein jojoba provided results comparable to those of feed withdrawal. Defatted jojoba meal (12%), incorporated into ration after a one day fast resulted in high weight loss and complete cessation of lay followed by peak production (85%) within two weeks with egg quality comparable to that of a fasting diet. However, because this diet included a one day fast, it would not meet UEP Guidelines.

Cottonseed meal - an easily available, inexpensive by-product of cottonseed - added at the rate of 20%, 40% and 50% was used in a moult diet to produce results similar to those of feed withdrawal with the exception of low feed consumption (Table 2). It was recommended that cottonseed meal be coarsely ground to avoid selective feeding (Davis et al., Reference DAVIS, LORDELO and DALE2002). Another possibility for low feed consumption of cottonseed meal is its content of gossypol, an anti-nutrient for poultry.

As shown in Table 2, wheat middlings fed for 28 days produced cessation of lay (Biggs et al., Reference BIGGS, DOUGLAS, KOELKEBECK and PARSONS2003) by the 8th day. Combinations such as 71% wheat middlings and 23% corn or 95% wheat middlings with corn produced post moult production values comparable to results for feed withdrawal methods (Biggs et al., Reference BIGGS, DOUGLAS, KOELKEBECK and PARSONS2003; Reference BIGGS, PERSIA, KOELKEBEC and PARSONS2004).

Landers et al. (Reference LANDERS, WOODWARD, LI, KUBENA, NISBET and RICKE2005) suggested use of a 100% alfalfa diet to achieve results comparable to those of feed withdrawal (Table 2). Both alfalfa meal and pellets efficiently induced moult. However, 90% alfalfa produced better results than those of 70% and 100% inclusion (Donaldson et al., Reference DONALDSON, KIM, WOODWARD, HERRERA, KUBENA, NISBET and RICKE2005). Alfalfa, a high protein, high fibre diet with the slowest passage through the gut produced a feeling of satiety (Sibbald, Reference SIBBALD1979). In addition, research by Woodward et al. (Reference WOODWARD, LKWON, KUBENA, BYRD, MOORE, NISBET and RICKE2005) showed lower concentrations of S. enteritidis in the intestine as compared to a traditional moult.

Several investigations were conducted to further reduce the incidence of S. enteritidis during moulting induced with alfalfa. Fructo-oligosaccharide (FOS) at 0.750% and 0.375% in a 90% alfalfa diet (Dunkley et al., Reference DUNKLEY, MCREYNOLDS, HUME, DUNKLEY, CALLAWAY, KUBENA, NISBET and RICKE2007) and chlorate products in water (McReynolds et al., Reference MCREYNOLDS, KUBENA, BYRD, ANDERSON, RICKE and NISBET2005) decreased the incidence of S. enteritidis. Moreover, mushroom or pokeweed extracts combined with alfalfa meal markedly decreased stress, thereby reducing pathogenic infections. Significant ovarian regression and improvement in post-moult production were noted in an alfalfa diets supplemented with pokeweed extract and full fed pokeweed extract (Willis et al., Reference WILLIS, GOKTEPE, ISIKHUEMHEN, REED, KING and MURRAY2008).

Mansoori et al. (Reference MANSOORI, MODIRSANEI, FARKHOY, KIAEI and HONARZAD2007) reported that tomato pomace produced similar or superior performance to that of feed withdrawal and alfalfa meal. Additionally, a higher egg yolk score was reported by tomato pomace fed hens. Less stress was reported for hens fed tomato pomace as compared to other treatments.

Barley grain (100%) had performance comparable to or better than that (in terms of post-moult production and egg quality) of alfalfa (Petek and Alpay, Reference PETEK and ALPAY2008). Rice bran and cumin seed diets produced results equivalent to that of alfalfa meal though there was less feed consumption for cumin seeds due to tannin content (Mansoori et al., Reference MANSOORI, MODIRSANEI, FARKHOY, KIAEI and HONARZAD2007).

Forced moulting was simulated by feeding hens during the morning of the first day and during the evening of the next day for 32 days. This pattern resulted in rejuvenation of the reproductive tract similar to that of a traditional moult (Ruszler and Novak, Reference RUSZLER and NOVAK2006).

An increasing global need for unconventional feedstuffs

Egg production is predicted to rise to 71 million tons in 2015; this is a 10.889 million tonne increase from 2005 (Evans, Reference EVANS2008). Due to an increasing population and subsequent increased demand, a marked production hike is occurring in countries like China, India, Thailand, Mexico and Argentina. These developing countries are surpassing European countries in egg production (Edward, Reference EDWARD2007). The cost of production plays an important role in sustaining the global egg market. Non-conventional feed sources can generate equivalent production at significantly lower cost as feed contributes up to 70% of production costs (Mireles, Reference MIRELES2009). Moreover, increasing feed prices of conventional corn/soy diets due to diversion of corn into ethanol, undoubtedly, will contribute to cost (Yegani, Reference YEGANI2007).

Unconventional feedstuffs such as coconut and cumin seed meals are successfully used in layer and non feed removal moults in Asian and Middle Eastern countries (Ravindran and Blair, Reference RAVINDRAN and BLAIR1992; Mansoori et al., Reference MANSOORI, MODIRSANEI, FARKHOY, KIAEI and HONARZAD2007). In the western U.S., local ingredients like safflower meal and tomato pomace are promising alternatives. Safflower is a minor crop commercially produced in more than sixty countries - mainly in India, the U.S., Mexico, Argentina, Ethiopia and Australia. In the U.S., safflower production in 2007 was 94,827.586 tonnes, worth $39.2 million (U.S.). California contributed 50% of the total U.S. production (Boland, Reference BOLAND2009). Safflower is used as colouring and flavouring agents in foods, in manufacturing dyes, paints, cosmetics, medicines, and as cooking oil (extracted from seed). Safflower seed contains high fibre (50%) and dehulling results in a reduction (4-20%) in fibre content (Leeson and Summers, Reference LEESON and SUMMERS1997). Safflower meal is an alternative source of protein when supplemented with lysine and methionine (McNab and Boorman, Reference MCNAB and BOORMAN2002) and is a good source of α-tocopherol and carthamin (Ekin, Reference EKIN2005). Results of investigations noted superior growth performance for ruminants as well as poultry, indicating that safflower meal can partially replace protein sources like soybean meal (Kohler et al., Reference KOHLER, KUZMICKY, PALTER, GUGGOLZ and HERRING1966).

Tomato pomace is a high protein (20-24%), high fibre (30-35%) by-product with low energy (Drouliscos, Reference DROULISCOS1976; Arana et al., Reference ARANA, DEPETERS, FADEL, PAREAS, PEREZ-MONTI, OHANESIAN, ETCHEBARNE, HAMILTON, HINDERS, MALONEY, OLD and RIODAN2000; King and Zeidler, Reference KING and ZEIDLER2004; Assi and King, Reference ASSI and KING2008; National Feed and Grain Council, 2009). It consists of peels, cores, culls, trimmings, seeds, liquor and unprocessed green tomatoes picked by harvest machinery. Furthermore, it contains antioxidants including carotenoids, α-tocopherol, lutein, and lycopene (King and Zeidler, Reference KING and ZEIDLER2004; Assi and King, Reference ASSI and KING2008). California and Florida lead the U.S. in production of tomatoes for processing in 2008, 10.889 million tonnes of processing tomatoes were produced (Boriss, Reference BORISS2009). Hence this pomace is an easily available, abundant, and inexpensive by-product of tomato processing that has potential for successful incorporation into animal feed (Haddadin et al., Reference HADDADIN, ABU-REESH., F.A.S. and ROBINSON2001). Ruminants are fed wet pomace in combination with wheat to improve growth performance (Denek and Can, Reference DENEK and CAN2006). Reportedly, pomace is added to pet food to enhance palatability (Holistic Natural Pet Food, Reference HOLISTIC NATURAL PET FOOD2008).

Due to its high content of α-tocopherol, King and Zeidler (Reference KING and ZEIDLER2004) suggested use of tomato pomace in poultry feed for reduction of lipid oxidation of post mortem poultry food products. As mentioned previously, dry tomato pomace performs significantly better in producing moult and post-moult performance measurements when compared to those of alfalfa meal (Mansoori et al., Reference MANSOORI, MODIRSANEI, FARKHOY, KIAEI and HONARZAD2007). Patwardhand et al. (2010) found that hens fed 70% tomato pomace in a low salt corn/soy diet exhibited more observed diarrhoea and lost a greater percentage of body weight than those fed other experimental diets when compared to a control. During post moult, hens fed tomato pomace and those fed safflower meal (43.51%) had equal performance and egg quality measurements except for egg production. Overall, these investigators recommended feeding tomato pomace at less than 70% of the diet for only two weeks when body weight is 85% of that for the control. Alternatively, pomace could be fed at lower concentrations in diets.