ENVIRONMENT, WELL-BEING, AND BEHAVIOR The effect of dietary alterations during rearing on feather condition in broiler breeder females K. L. H. Morrissey,*†1 T. Widowski,* S. Leeson,* V. Sandilands,† A. Arnone,*‡ and S. Torrey*‡ *Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada; †Avian Science Research Centre, Scotland’s Rural College, Ayr KA6 5HW, United Kingdom; and ‡Agriculture and Agri-Food Canada, Guelph, Ontario N1G 5C9, Canada Six body parts (neck, back, wings, legs, vent area, tail) were given a score from 0 to 5 (0 = no feather damage, and 5 ≥ 50% feather loss with tissue damage). Scores were summed for each bird and averaged for each pen. Data were analyzed with room and feeding frequency as main factors and diet as the subfactor with repeated measures. There was an interaction between diet and time (P < 0.01) with the feather condition of the C birds worsening more quickly in comparison with the F and P birds. There was an interaction between feeding frequency and time (P = 0.015), with SAD-fed birds scoring better than daily-fed birds at 20, 26, and 36 wk. This interaction could indicate that SAD feeding increased satiety after the birds became accustomed to the schedule. Because feather condition was better with the alternative diets, this may indicate a reduction in stereotyped feather pecking with these diets. This suggests that the alternative diets increase satiety compared with the control diets.
Key words: broiler breeder, hunger, skip-a-day, feather scoring, feather pecking 2014 Poultry Science 93:1–8 http://dx.doi.org/10.3382/ps.2013-03822
INTRODUCTION
motivation (Mench, 2002; Hocking and Jones, 2006). Broiler breeder females are routinely beak trimmed to avoid damage caused by feather pecking, aggression, and cannibalism (de Jong and Guémené, 2011) even though there are a limited number of reports of injurious pecking causing widespread problems in broiler breeder flocks (Guy, 2001; Hocking and Jones, 2006; Morrissey et al., 2014). However, de Jong and Guémené (2011) reported that although most feather and skin damage is probably caused by mating, feather pecking may also have an impact (especially before sexual maturity). Feather pecking is the most common behavioral problem evident within the poultry industry (Blokhuis, 1986; Bilcik and Keeling, 1999; Lambton et al., 2010). The behavior can be divided into 2 subcategories: gentle feather pecking, where feathers are nibbled and pecked at but not removed, and severe feather pecking, where feathers are pulled firmly and often removed
Broiler breeders are bred specifically to produce fast-growing progeny, the modern-day broiler chicken. Because broiler breeders have the genetic potential to grow as quickly and efficiently as their broiler offspring, they must be severely feed restricted throughout the rearing period to ensure optimal health and avoid obesity (D’Eath et al., 2009). However, the severe quantitative feed restriction necessary for reproductive success results in chronic hunger and broiler breeders often display high levels of oral stereotypic behavior and aggression associated with hunger or frustrated feeding
©2014 Poultry Science Association Inc. Received December 11, 2013. Accepted February 25, 2014. 1 Corresponding author: [email protected]
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ABSTRACT In commercial production, broiler breeders are severely feed restricted to maintain healthy BW. This restriction can induce stereotypic behavior, including feather pecking, which has negative welfare implications for both the victim and performer. It has been suggested that the problem may be symptomatic of chronic hunger or the frustration of feeding motivation. In this study, we determined whether feather condition, as an indirect measure of feather pecking, could be improved via dietary manipulation. Six dietary treatments were tested, each with 5 replicate pens of 9 to 12 birds. Control diets (C) were fed on a daily or skip-a-day (SAD) basis. Alternative diets included soybean hulls as a bulking ingredient and calcium propionate (CaP) as an appetite suppressant of either a feed grade (F) or purified (P) quality. Both alternative diets were fed on either a daily or SAD basis. Five or 6 birds were randomly chosen from each pen and feather scored at 10, 14, 20, 26, and 36 wk of age.
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hens fed a qualitatively restricted diet compared with those fed a commercial quantitatively restricted diet in combination with alternative feeding schedules. In addition, differences between 2 qualities of CaP used in conjunction with high fiber diets were assessed. Feather condition scoring was used as an indicator for feather pecking behavior. Birds reared on diets associated with a reduction in hunger (i.e., qualitatively restrictive diets) were expected to perform less stereotypic pecking, including feather pecking, and therefore have better feather condition scores, and we hypothesized that the differences would be most apparent with using a purified quality of CaP. Because SAD feeding is generally considered to reduce welfare, it was hypothesized that the birds fed on a daily basis would be less hungry and would have better feather condition scores compared with their SAD-fed counterparts.
MATERIALS AND METHODS This experiment was performed in conjunction with Morrissey et al. (2014) using the same birds. All of the procedures used in this experiment were approved by the University of Guelph’s Animal Care Committee and were in accordance with the guidelines outlined by the Canadian Council for Animal Care.
Birds One-day-old Ross 708 broiler breeder females (n = 383) and males (n = 51) were donated (courtesy of Aviagen, via Horizon Poultry, Hanover, ON, Canada) for this experiment and reared at the OMAFRA Arkell Poultry Research Station (Guelph, ON, Canada). Males and females were reared separately. All of the birds were vaccinated against local diseases in accordance with the research farm’s vaccination protocol and reared according to the programs outlined by the breeding company (Aviagen, 2007). All birds were beak trimmed at 1 d of age at the hatchery using an infrared beam to minimize potential damage caused by feather pecking. In addition, the male chicks underwent routine spur removal at 1 d of age. For the first 3 d of life, birds were housed with a lighting regimen of 23L:1D at 20 lx. From then on the lighting schedule was as follows: 12L:12D (20 lx) from d 4 to 21, 8L:16D (4 to 7 lx) from d 22 to wk 22, 14L:10D (9 to 20 lx) from wk 22 to 24, 15L:9D (9 to 20 lx) from wk 24 to 26, and 16L:8D (9 to 20 lx) from wk 26 onward. Measured light intensity was 6.1 ± 1.6 lx in rearing and 15.0 ± 3.1 lx in lay. Rooms were heated to 32°C for the first 2 d and then gradually cooled to 21°C from 6 wk onward. Additionally, chicks were provided with a heated mat until 7 d of age. Upon arrival to the research farm, the female chicks were randomly allocated to 1 of 30 identical pens (1.83 × 2.36 m) that had been assigned 1 of 6 treatments. All of the pens had wood shavings (approximately 3 cm depth) covering the entire floor. Each pen was furnished with a wooden perch (0.05 × 0.05 × 1.52 m,
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(Dixon, 2008). Both types of feather pecking can reflect a negative state of well-being for both the performing and recipient birds. However, it is the severe type that can represent an economic loss to the industry (Lambton et al., 2010) because it is correlated with outbreaks of cannibalism (Leeson and Walsh, 2004; Dixon, 2008), decreased egg production, and increased morbidity and mortality (Mench, 2002). In addition, feather pecking is painful for the recipients and increases heat loss if large parts of the body become denuded, in turn increasing the cost of metabolic maintenance (Bilcik and Keeling, 1999; LaBrash and Scheideler, 2005). Although feather pecking appears to be a multifactorial problem caused by internal motivational states and external eliciting factors (Leeson and Walsh, 2004; Van Krimpen et al., 2005; Dixon, 2008), in broiler breeders, it may fall under the category of oral stereotypic behavior indicative of chronic hunger and frustrated feeding motivation. Researchers have attempted to alleviate chronic hunger and the associated symptoms in broiler breeder pullets using alternative diets (Savory and Larivière, 2000; Hocking et al., 2004; de Jong et al., 2005; Sandilands et al., 2006). To date, the most effective diets contain both a high-fiber component and a chemical compound (calcium propionate; CaP) acting as an appetite suppressant (Sandilands et al., 2005, 2006). There have been a wide range of behavioral benefits of these diets, with differences among experiments potentially associated with the quality of CaP (Savory and Larivière, 2000). Savory and Larivière (2000) were not able to reproduce the effects of a highly purified CaP (such as reduced symptoms of hunger and controlled growth rates; Savory et al., 1996) as effectively with an industrial or feed-grade chemical. Sandilands et al. (2006) were able to almost completely abolish the performance of object pecking in broiler breeders fed a diet containing a high-fiber component and CaP. However, most of the effective alternative diets have been fed on an ad libitum basis (Savory et al., 1996; Sandilands et al., 2005, 2006), which is not common practice in commercial production. It is common for North American broiler breeder producers to adopt alternative feeding schedules on which birds may not be fed every day (Bramwell et al., 2008). Skip-a-day (SAD) is the most commonly used alternative feeding schedule, where birds are fed twice their daily allocation every other day (Bramwell et al., 2008). Because the birds are not receiving feed on a daily basis, these alternative feeding regimens are considered to be detrimental to an animal’s well-being and are banned in the United Kingdom (DEFRA, 2007). There is some research describing feed efficiency and production in broiler breeders being fed using alternative feeding regimens (Bennett and Leeson, 1989; Ingram et al., 2001; de Beer and Coon, 2007). However, there was no research pertaining to the welfare implications of SAD feeding alone or in combination with alternative diets. The objectives of this experiment were to assess the differences in feather condition of broiler breeder
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Table 1. Concentrations (g/kg) of soybean hulls (SBH) and calcium propionate (in feed-grade form, CaP-F, or purified form CaP-P) supplemented in treatment diets (C, commercial control; F, fiber and feed-grade CaP; P, fiber and purified CaP)1 Starter
Grower 1
Grower 2
Diet type
SBH
CaP-F
CaP-P
SBH
CaP-F
CaP-P
SBH
CaP-F
CaP-P
C F P
— 400 400
— 10 —
— — 10
— 400 400
— 30 —
— — 30
— 400 400
— 50 —
— — 50
1Inclusion levels of CaP increased with each period (starter 0 to 6 wk; grower 1, 6 to 12 wk; and grower 2, 12 to 22 wk). All treatments received a daily-fed commercial control diet after 22 wk as a layer crumble (not indicated here).
Experimental Protocol Prior to starting the experimental diets, birds were redistributed at 18 d of age and pens were standardized to an average weight as close to the overall mean as possible (308.72 ± 1.00 g/bird) by removing 1 or 2 birds/pen. This left 18 pens with 11 birds and 12 pens with 12 birds. At 20 wk, 22 of the smallest and least thrifty birds were culled (0, 1, or 2 birds/pen). During the rearing period (0 to 22 wk), 2 birds were found dead and 7 were euthanized due to injury, infection, sexing error, or beak deformities. During the laying period (22 to 37 wk), 2 birds were found dead and 15 were euthanized due to lameness and injury. Dietary Treatments. This experiment was a 3 × 2 factorial design, with 3 different diets and 2 feeding regimens. The 2 feeding regimens tested were daily feeding and SAD feeding, where birds received twice the daily allocation every other day. Alternate feeding regimens commenced once the birds reached 4 wk of age and birds were switched back to daily feeding at 22 wk. The 3 experimental diets tested were a commercial (C) diet, and 2 diets containing soybean hulls (SBH) and either a feed-grade quality (F) or purified (P) appetite suppressant (CaP; Table 1). Therefore, there were 2 treatment groups that were fed the same diet, with one fed daily and the other fed on a SAD basis, for all 3 diet types. A total of 4 rooms were used to house the birds
(12 pens/room total), with 2 rooms for daily birds and 2 rooms for SAD birds. To avoid disruption to birds not being fed while others were, daily and SAD birds were not housed in the same rooms, thereby confounding room with feeding frequency. One of the rooms housing the daily fed birds was also used to house the males used for this experiment (4 pens) and other females used for another experiment (4 pens). Therefore, one pen of each daily-fed diet types was housed in 3 of the last remaining 4 pens. In the other room housing daily-fed birds, 4 pens of each diet type were randomly distributed within the room. Two rooms were used to house the SAD birds; diet types as evenly distributed across rooms as possible, with 4 or 5 pens empty in each of the rooms. Diets that contained SBH and CaP were composed of a basal amount of the commercial crumble and were diluted with SBH (400 g/kg) and CaP (Table 1). As the birds matured, the inclusion rate of CaP increased; starter included 10 g of CaP/kg, grower 1 included 30 g of CaP/kg, and grower 2 included 50 g/kg. However, for the first 18 d, all birds were fed a commercial chick starter (2.86 Mcal/kg, CP = 18%, Table 2). All birds were fed daily following lights-on at 0800 h. Following breeder recommendations, all birds were fed on an ad libitum basis for the first week of life and then subsequently feed restricted from d 8 onward. All diets were formulated according to age of the bird: starter crumble from 0 to 6 wk, grower 1 crumble from 6 to 12 wk, grower 2 crumble from 12 to 22 wk, and layer crumble from 22 wk onward. The starter and grower diets were analyzed at Agri-Food Laboratories in Guelph, ON (Table 2). The layer diet was not analyzed; however, all birds were fed the same commercial layer crumble during the laying period. All treatments were fed the commercial starter diet from 1 to 19 d of age. On d 19, birds in the F and P treatments were switched from the commercial starter crumble to the alternative starter diet. Birds in these treatments were allocated a larger volume of feed due to the fibrous dilution and inclusion of CaP in the F and P diets. This increase depended on the age of the bird: 41, 43, and 45% more feed for starter, grower 1, and grower 2, respectively. At 22 wk of age, just before coming into lay, all birds were fed the commercial layer diet and SAD birds were switched to daily feeding. Data were collected until birds reached 36 wk of age.
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with top edges bevelled) at a height of 20 cm. Nest boxes (0.91 × 0.46 m, with 3 nest sites each measuring 0.30 m in width) were added at wk 20 to allow the birds to become accustomed before the onset of lay. Water was provided on an ad libitum basis from a nipple drinker (7 nipples/pen). Round pan feeders (38.1 cm in diameter) were used until the birds were 10 wk old. Hanging trough-style feeders (0.13 × 1.52 m) with exclusion grills were then installed to allow for more space per bird during feeding. At 22 wk, one rooster was added to each pen of hens to simulate commercial farm settings. Rooster feeders were installed before combining sexes and roosters were fed separately from the hens, following breeder guidelines. Birds were housed until they were 37 wk of age. Pens were cleaned out as needed; however, whenever dirty pens were cleaned out, all other pens received at least a top layer of fresh wood shavings.
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Table 2. Composition of C (commercial control), F [fiber and feed-grade calcium propionate (CaP)], and P (fiber and purified CaP) diets used in starter (S, 0 to 6 wk), grower 1 (G1, 6 to 12 wk), and grower 2 (G2, 12 to 22 wk) C Item
1Analyzed
P
S
G1
G2
S
G1
G2
S
G1
G2
60.6 8.8 24.0 3.14 2.0 0.34 1.0 0.12 — — 9.03 17.07 1.72 1.31 11.31 3.87 2.62 2,480
60.8 16.0 16.5 3.13 2.1 0.36 1.0 0.11 — — 9.98 15.65 1.93 1.62 11.17 3.28 2.43 2,480
60.8 16.0 16.5 3.13 2.1 0.36 1.0 0.11 — — 8.26 14.92 1.06 0.87 12.93 3.25 2.89 2,680
35.8 5.2 14.2 1.30 1.2 0.20 0.59 0.07 1.44 40.0 9.24 16.06 1.95 1.09 26.48 12.97 1.46 1,890
36.0 8.8 9.8 0.65 1.2 0.21 0.59 0.06 3.19 39.5 11.25 14.72 1.95 1.06 26.81 14.42 1.64 1,680
35.2 8.1 9.6 — 1.2 0.21 0.58 0.06 5.05 40.0 8.58 12.84 2.70 1.51 29.84 15.04 1.48 1,780
35.8 5.2 14.2 1.30 1.2 0.20 0.59 0.07 1.44 40.0 6.73 12.02 2.26 1.22 28.93 14.06 1.92 1,810
36.0 8.8 9.8 0.65 1.2 0.21 0.59 0.06 3.19 39.5 9.55 9.72 1.70 0.87 24.42 10.89 2.47 2,030
35.2 8.1 9.6 — 1.2 0.21 0.58 0.06 5.05 40.0 8.11 12.63 2.65 1.36 43.35 14.80 1.87 1,760
at Agri-Food Laboratories, Guelph, ON, Canada.
Feather Scoring. Feather scoring was performed when the birds were 10, 14, 20, 26, and 36 wk of age (only females scored). At each time point, 5 or 6 birds/ pen were randomly chosen, weighed, and then feather scored. Six body parts, including the neck, back, wings, legs, vent, and tail, were assessed and given a score from 0 to 5 (scoring system adapted from Bilcik and Keeling, 1999; LaBrash and Scheideler, 2005; Bright et al., 2006; Table 3). The highest (worst) possible total feather score for each bird was 30 (i.e., bird completely denuded including tissue damage).
Data Analysis The statistical analyses for this experiment were performed using the SAS statistical analysis package (SAS 9.2, 2007, SAS Institute Inc., Cary, NC). At each time point, the scores for all 6 body parts were summed for each bird and then averaged for each pen. A mixed model ANOVA with repeated measures was performed on pen means with age, diet type, and feeding frequency as the main factors. Room and room × feeding frequency were accounted for as random effects. Room × feeding frequency was included as a random effect
because feeding frequency was not randomized or evenly distributed across the 4 rooms. The analysis used for handling repeated measures over time was modeled after the method given by Wang and Goonewardene (2004), using a first order auto-correlation covariance structure. Data were +1 log-transformed to include scores of 0 and to normalize residuals before analyzing pen means. Orthogonal linear and quadratic contrasts were used to analyze differences in trends over time (rather than differences at specific ages) between diet types and frequencies. For contrasts involving diet type, overall means as well as trends across ages for C versus F + P and F versus P are reported.
RESULTS Feather scores throughout this experiment ranged from 0 to 14. Nine birds from the C treatment were the only birds with scores higher than 10. The highest score within the alternative diet treatments was 9 (daily F). There was a significant age effect because average feather damage increased with time (F4,71.1 = 33.37, P < 0.0001).
Table 3. Feather scoring scheme adapted from Bilcik and Keeling (1999), LaBrash and Scheideler (2005), Bright et al. (2006) Score
Description
0 1 2 3 4 5
Completely covered Slight damage: wet, broken feathers, up to 10% of feathers missing from a given area 10 to 50% of feathers missing from a given area (no blood or tissue damage) >50% of feathers missing from a given area (no blood or tissue damage) 10 to 50% of feathers missing from a given area including blood or tissue damage >50% of feathers missing from a given area including blood or tissue damage
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Ingredient Corn (%) Wheat shorts (%) Soybean meal (%) Limestone (%) Dicalcium phosphate (%) Salt (%) Vitamin-mineral premix (%) Methionine (%) CaP (%) Soybean hulls (%) Analyzed composition1 Moisture (%) CP (%) Ca:P ratio Calcium (%) NDF (%) Crude fiber (%) Fat (%) ME (kcal/kg)
F
FEATHER CONDITION IN BROILER BREEDER FEMALES
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Effect of Diet Type Overall, there was an effect of diet type (F2,16.2 = 8.90, P < 0.01). Orthogonal contrasts revealed a difference between the control diet and both alternative diets (F1,11 = 7.52, P = 0.019, Figure 1a) as well as a difference between the 2 alternative diets (F1,23.2 = 9.91, P < 0.01, Figure 1b). However, there was also an interaction of diet type with age (F8,52.3 = 3.35, P < 0.01, Figure 2a). The scores for all 3 diet types were similar at wk 10, but the C birds’ feather scores worsened much more quickly over time and were markedly worse at 36 wk compared with the F and P diets (Figure 2a).
Effect of Feeding Frequency There was no effect of feeding frequency on feather scores (F1,6.27 = 1.58, P = 0.25). There was, however, a significant interaction of frequency with age (F4,71.1 = 3.33, P = 0.015) with the daily-fed birds’ mean feather condition worsening more quickly over time than the
SAD-fed birds (Figure 2b). Both linear (F1,77.4 = 6.92, P = 0.010) and quadratic (F1,95.6 = 6.56, P = 0.012) trends differed over time between the daily and SAD feeding regimens.
DISCUSSION Feed restriction in broiler breeders is often associated with both stereotyped and aggressive pecking, 2 indicators of poor welfare. However, very little is known about the effect of alternative diets or feeding schedules on the feather condition of breeders during the rearing and production periods. In this experiment, all of the birds were relatively well-feathered (especially before the onset of lay). Very few birds showed any signs of tissue damage, with most of these cases resulting from bleeding feather follicles, not from direct pecking at the tissue. The birds used in this experiment were all beak trimmed and were housed in pens at low stocking densities on litter that was changed frequently, providing fresh substrate to support foraging and dustbathing. It
Figure 2. Effect of diet type (a) and feeding frequency (b) on mean feather scores (raw mean ± pooled SEM) from 10 to 36 wk of age. Trends over time differed between diet types (diet × age effect, P < 0.01), and frequencies (P = 0.015). Diet types include 1) commercial (C), 2) feed or industrial grade calcium propionate (CaP) + fiber (F), and 3) purified CaP + fiber (P). Feeding frequencies were either daily-fed or skip-a-day (SAD). Higher feather scores reflect worse feather condition; maximum score recorded was 14.
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Figure 1. Effect of diet type (raw mean ± pooled SEM) on mean feather score from 10 to 36 wk of age. Diet types include 1) commercial (C), 2) feed or industrial grade calcium propionate (CaP) + fiber (F), and 3) purified CaP + fiber (P). Contrasts uncovered significant differences, (a) C versus F + P, P = 0.019, and (b) F versus P, P < 0.01. Higher feather scores reflect worse feather condition; maximum score recorded was 14.
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Effect of Diet Type on Feather Condition From the data presented, it is clear that both alternative diet types (F and P) had a positive effect on feather condition. This finding supports our initial hypothesis, indicating a reduction in feather pecking from birds fed the alternative diets. However, it is impossible to determine whether the better feather condition is due to a decrease in pecking frequency, pecking severity, a combination of the 2, or something completely unrelated (i.e., feather damage associated with abrasions at the feeding trough). Dixon (2008) suggested that different motivational factors may influence the performance of gentle and severe pecking. Severe pecks were most similar in morphology to foraging pecks and may be caused by a lack of access to foraging substrates, whereas gentle pecking may be more closely related to preening behavior (Dixon, 2008). For the purpose of the current study, both gentle and severe feather pecking could be associated with chronic hunger because foraging is a component of feeding behavior and excessive preening or allo-preening could indicate redirected feeding frustration (Duncan and Wood-Gush, 1972). Therefore, a reduction in feeding frustration, or an increase in satiety would likely result in a reduction in both severe and gentle feather pecking. It seems, then, that both alternative diets (F and P) were effective at reducing hunger because feather damage increased more gradually in comparison with the feather condition of the birds reared on the C diet type. Behavior of these birds was recorded and reported elsewhere (Morrissey et al.,
2014); feather pecking was observed more frequently in the C treatments during rearing than both the F and P diets, with differences disappearing during the production period. No differences in feather pecking were observed between the 2 alternative diet types. The addition of fiber itself may have inherent effects on feather pecking and subsequent feather condition, without being directly hunger-related. There is some evidence that high-fiber diets have beneficial effects on laying hen welfare, where reaching satiety is not of concern because laying hens are generally fed ad libitum. Steenfeldt et al. (2007) reported a reduction in severe feather pecking and an improvement in feather condition at 53 wk of age for laying hens fed diets supplemented with silage or carrots compared with those fed a standard control diet. In addition, feather eating may serve as a means for increasing dietary fiber; Harlander-Matauschek et al. (2006a) showed that laying hens from a high feather pecking line worked significantly harder (i.e., pecked more at a key) for access to feathers, as well as wood shavings (although this difference was only numerical), than hens from a low feather pecking line. Feather eating increases the speed of food passage within the digestive tract, acting similarly to insoluble fibers, suggesting that a lack of sufficient dietary fiber increases the risk of feather pecking, especially for birds already prone to high levels of feather pecking (Harlander-Matauschek et al. 2006b). Previous studies including CaP within alternative diets for broiler breeders have used either a purified or industrial grade quality of the chemical (Savory et al., 1996; Savory and Larivière, 2000; Sandilands et al., 2005, 2006). However, Savory and Larivière (2000) suggested that the purified CaP used in a previous experiment (Savory et al., 1996) was more effective than the industrial grade version at both reducing symptoms of hunger and controlling growth rates when fed ad libitum. The results from the current study suggest that both grades of CaP were able to reduce hunger in comparison with the control diet, reflected by the improvement in feather condition. In fact, from 10 to 36 wk of age, average feather condition was better for birds fed the diet containing the industrial grade CaP (F). Based on the analyzed contents of each diet type (Table 2), it is possible that the differences in CP between the F and P diets were partly responsible for differences in feather condition. Ambrosen and Petersen (1997) demonstrated that laying hens fed diets with less than 15.2% CP had significantly worse plumage scores than those fed diets with 16.5 to 19.3% CP. The reason for this reduction in CP in the P diets is unclear and may be the result of an error during feed mixing at the feed mill. It is arguable that the better feather condition with both the F and P diets were not a result of a reduction in hunger, but rather of a reduction in general activity due to a feeling of malaise. The CaP has a very pungent smell and the birds may find it aversive (Buckley et al., 2011) or it may make them feel ill. Whereas Buckley et al. (2011) and Savory et al. (1996) found that birds had
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was also common practice at the research facility to apply pine tar to large denuded areas of the body to prevent further damage. These factors may have affected the level of feather pecking; however, there were still obvious and significant differences between treatments. Feather damage increased over time for all treatment groups. However, changes after 22 wk may have been the result of the addition of the roosters to the pens. Scores from the back and neck region may have specifically been influenced by the roosters, as broiler breeder males are vigorous during mating and can pull out feathers in the process (Millman et al., 2000). However, it was impossible to identify what degree of damage the roosters were responsible for, so all scores were included in the analyses. It is also necessary to note that all treatments were fed the same commercial diet from 22 wk onward. However, it can be assumed that differences in feather condition observed at 26 and 36 wk of age are indirectly related to dietary treatments as some carry-over effects from rearing have been previously demonstrated. Both Blokhuis and Van der Haar (1989) and Johnsen et al. (1998) found that rearing environments played a significant role in the development of feather pecking during the production period. In their experiments, chicks reared on wire feather pecked more later in life than chicks that had been reared with access to a foraging and dustbathing substrate.
FEATHER CONDITION IN BROILER BREEDER FEMALES
a slight preference for a control diet over a diet including CaP, this preference was not exclusive and birds still consumed the alternative diet.
Effect of Feeding Frequency on Feather Condition
Conclusions The results of this experiment supported our first hypothesis that high-fiber diets including an appetite suppressant would improve feather condition; however, the industrial grade CaP resulted in better feather condition than the purified chemical. Similar diets in previous research have been shown to reduce hunger and feeding motivation compared with commercially restricted birds. Therefore, it appears that a reduction in feather damage represents a reduction in hunger. The F diet was the most effective at improving feather
condition, indicating that it may have been most effective at reducing hunger. Interestingly, our hypothesis that SAD feeding would result in poorer feather condition scores and would therefore negatively affect welfare proved incorrect. The SAD feeding actually delayed the decrease in feather condition over time. The feather scores of the dailyfed birds worsened at a quicker rate, suggesting that SAD birds grew accustomed to their feeding schedule over time and learned when to expect feed. On “onfeed” days, they may have been receiving enough feed to satisfy their hunger. The ability to reach satiety every other day may be more welfare friendly than never feeling full on a daily feeding schedule. Not only does better feather condition suggest that birds on alternative diets are experiencing different levels of satiety, but increased feather cover can also act to protect the hens against tissue damage and subsequent infection during mating in the production period.
REFERENCES Ambrosen, T., and V. E. Petersen. 1997. The influence of protein level in the diet on cannibalism and quality of plumage of layers. Poult. Sci. 76:559–563. Aviagen. 2007. Parent Stock Management Manual: Ross 708. Aviagen, Ltd., Huntsville, AL. Bennett, C. D., and S. Leeson. 1989. Growth of broiler breeder pullets with skip-a-day versus daily feeding. Poult. Sci. 69:836–838. Bilcik, B., and L. J. Keeling. 1999. Changing in feather condition in relation to feather pecking and aggressive behaviour in laying hens. Br. Poult. Sci. 40:444–451. Blokhuis, H. J. 1986. Feather-pecking in poultry: Its relation with ground pecking. Appl. Anim. Behav. Sci. 16:63–67. Blokhuis, H. J., and J. W. Van der Haar. 1989. Effects of floor type during rearing and of beak trimming on ground pecking and feather pecking in laying hens. Appl. Anim. Behav. Sci. 22:359–369. Bramwell, R. K., J. R. Moyle, D. E. Yoho, and B. S. Harper. 2008. Weighing broiler breeder females post-feeding. Accessed Jun. 20, 2012. http://www.thepoultrysite.com/articles/1111/weighingbroiler-breeder-females-postfeeding. Bright, A., T. A. Jones, and M. S. Dawkins. 2006. A non-intrusive method of assessing plumage condition in commercial flocks of laying hens. Anim. Welf. 15:113–118. Buckley, L. A., V. Sandilands, B. J. Tolkamp, and R. B. D’Eath. 2011. Quantifying hungry broiler breeder dietary preferences using a closed economy T-maze task. Appl. Anim. Behav. Sci. 133:216–227. D’Eath, R. B., B. J. Tolkamp, I. Kyriazakis, and A. B. Lawrence. 2009. ‘Freedom from hunger’ and preventing obesity: The animal welfare implications of reducing food quantity or quality. Anim. Behav. 77:275–288. de Beer, M., and C. N. Coon. 2007. The effect of different feed restriction programs on reproductive performance, efficiency, frame size and uniformity in broiler breeder hens. Poult. Sci. 86:1927–1939. de Jong, I. C., L. H. Enting, A. van Voorst, and H. J. Blokhuis. 2005. Do low-density diets improve broiler breeder welfare during rearing and laying? Poult. Sci. 84:194–203. de Jong, I. C., and D. Guémené. 2011. Major welfare issues in broiler breeders. World’s Poult. Sci. J. 67:73–82. DEFRA. 2007. Schedule 1: General conditions under which farmed animals must be kept. In The Welfare of Farmed Animals (England) Regulations 2007. Accessed May 2012. http://www.legislation.gov.uk/uksi/2007/2078/schedule/1/made. Dixon, L. M. 2008. Feather pecking behavior and associated welfare issues in laying hens. Avian Biol. Res. 1:73–87.
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Feather condition worsened more quickly for birds that were fed daily compared with their SAD counterparts, particularly while the birds remained on different feeding frequencies (through 22 wk). Thereafter, SAD birds continued to have better feather condition than daily-fed birds, although all birds’ feather condition deteriorated at similar rates. Feather pecking behavior in the morning immediately following feeding did not differ between daily-fed and SAD-fed birds (Morrissey et al., 2014). The lack of difference in feather pecking behavior suggests that not all occurrences of feather pecking were observed or that daily-fed birds were performing more severe feather pecking, rather than gentle feather pecking. The differences in feather condition between daily and SAD birds did not support our original hypothesis that SAD-birds would show more severe symptoms of chronic hunger and therefore have worse feather condition. The difference in trends over time between the feeding frequencies may reflect the time it took for the birds to become accustomed to the SAD feeding schedule. As the birds grew accustomed to the SAD regimen, it is possible that they were reaching a higher level of satiety during “on-feed” days than daily feedings could allow. In an experiment with feedrestricted sows, Douglas et al. (1998) was able to demonstrate that interval feeding (once every 3 d) increased physiological parameters of satiety and reduced behavioral indicators of feeding frustration. For example, interval-fed sows had a more pronounced increase in blood glucose and cholecystokinin than their daily-fed counterparts (Douglas et al., 1998). Cholecystokinin is thought to be related to satiety because it has been implicated in the termination of feeding (Douglas et al., 1998; Moran et al., 1998). In addition, interval-fed sows were more inactive, drank less water, and performed less sham chewing than daily-fed sows (Douglas et al., 1998).
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Morrissey et al. Mench, J. A. 2002. Broiler breeders: Feed restriction and welfare. World’s Poult. Sci. J. 58:23–29. Millman, S. T., I. J. H. Duncan, and T. M. Widowski. 2000. Male broiler breeder fowl display high levels of aggression toward females. Poult. Sci. 79:1233–1241. Moran, T. H., L. F. Katz, C. R. Plata–Salaman, and G. J. Schwartz. 1998. Disordered food intake and obesity in rats lacking cholecystokinin A receptors. Am. J. Physiol. 274:R618–R625. Morrissey, K. L. H., T. Widowski, S. Leeson, V. Sandilands, A. Arnone, and S. Torrey. 2014. The effect of dietary alterations during rearing on growth, productivity, and behavior in broiler breeder females. Poult. Sci. 93:285–295. Sandilands, V., B. Tolkamp, C. Savory, and I. Kyriazakis. 2006. Behaviour and welfare of broiler breeders fed qualitatively restricted diets during rearing: Are there viable alternatives to quantitative restriction? Appl. Anim. Behav. Sci. 96:53–67. Sandilands, V., B. J. Tolkamp, and I. Kyriazakis. 2005. Behaviour of food restricted broilers during rearing and lay—Effects of an alternative feeding method. Physiol. Behav. 85:115–123. Savory, C., and J. Larivière. 2000. Effects of qualitative and quantitative food restriction treatments on feeding motivational state and general activity level of growing broiler breeders. Appl. Anim. Behav. Sci. 69:135–147. Savory, C. J., P. M. Hocking, J. S. Mann, and M. H. Maxwell. 1996. Is broiler breeder welfare improved by using qualitative rather than quantitative food restriction to limit growth rate? Anim. Welf. 5:105–127. Steenfeldt, S., J. B. Kjaer, and R. M. Engberg. 2007. Effect of feeding silages or carrots as supplements to laying hens on production performance, nutrient digestibility, gut structure, gut microflora and feather pecking behaviour. Br. Poult. Sci. 48:454–468. Van Krimpen, M. M., R. P. Kwakkel, B. F. J. Reuvekamp, C. M. C. Van Der Peet-Schwering, L. A. Den Hartog, and M. W. A. Verstegen. 2005. Impact of feeding management on feather pecking in laying hens. World’s Poult. Sci. J. 61:663–686. Wang, Z., and L. A. Goonewardene. 2004. The use of MIXED models in the analysis of animal experiments with repeated measures data. Can. J. Anim. Sci. 84:1–11.
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Douglas, M. W., J. E. Cunnick, J. C. Pekas, D. R. Zimmerman, and E. H. von Borell. 1998. Impact of feeding regimen on behavioral and physiological indicators for feeding motivation and satiety, immune function, and performance of gestating sows. J. Anim. Sci. 76:2589–2595. Duncan, I. J. H., and D. G. Wood-Gush. 1972. Thwarting of feeding behaviour in the domestic fowl. Anim. Behav. 20:444–451. Guy, J. 2001. Environmental enrichment for broilers—Will it prevent feather pecking? World Poult. 17:22–23. Harlander-Matauschek, A., C. Baes, and W. Bessei. 2006a. The demand of laying hens for feathers and wood shavings. Appl. Anim. Behav. Sci. 101:102–110. Harlander-Matauschek, A., H. P. Peipho, and W. Bessei. 2006b. The effect of feather eating on feed passage in laying hens. Poult. Sci. 85:21–25. Hocking, P. M., and E. K. M. Jones. 2006. On-farm assessment of environmental enrichment for broiler breeders. Br. Poult. Sci. 47:418–425. Hocking, P. M., V. Zaczek, E. K. M. Jones, and M. G. Macleod. 2004. Different concentrations and sources of dietary fibre may improve the welfare of female broiler breeders. Br. Poult. Sci. 45:9–19. Ingram, D. R., L. F. Hatten, and B. N. McPherson. 2001. Effects of initiation age of skip-a-day feed restriction on skeletal development in broiler breeder males. J. Appl. Poult. Res. 10:16–20. Johnsen, P. F., K. S. Vestergaard, and G. Nørgaard–Neilsen. 1998. Influence of early rearing conditions on the development of feather pecking and cannibalism in domestic fowl. Appl. Anim. Behav. Sci. 60:25–41. LaBrash, L. F., and S. E. Scheideler. 2005. Farm feather condition score survey of commercial laying hens. J. Appl. Poult. Res. 14:740–744. Lambton, S. L., T. G. Knowles, C. Yorke, and C. J. Nicol. 2010. The risk factors affecting the development of gentle and severe feather pecking in loose housed laying hens. Appl. Anim. Behav. Sci. 123:32–42. Leeson, S., and T. Walsh. 2004. Feathering in commercial poultry. II. Factors influencing feather growth and feather loss. World’s Poult. Sci. J. 60:52–63.
Key words: broiler breeder, hunger, skip-a-day, feather scoring, feather pecking 2014 Poultry Science 93:1–8 http://dx.doi.org/10.3382/ps.2013-03822
INTRODUCTION
motivation (Mench, 2002; Hocking and Jones, 2006). Broiler breeder females are routinely beak trimmed to avoid damage caused by feather pecking, aggression, and cannibalism (de Jong and Guémené, 2011) even though there are a limited number of reports of injurious pecking causing widespread problems in broiler breeder flocks (Guy, 2001; Hocking and Jones, 2006; Morrissey et al., 2014). However, de Jong and Guémené (2011) reported that although most feather and skin damage is probably caused by mating, feather pecking may also have an impact (especially before sexual maturity). Feather pecking is the most common behavioral problem evident within the poultry industry (Blokhuis, 1986; Bilcik and Keeling, 1999; Lambton et al., 2010). The behavior can be divided into 2 subcategories: gentle feather pecking, where feathers are nibbled and pecked at but not removed, and severe feather pecking, where feathers are pulled firmly and often removed
Broiler breeders are bred specifically to produce fast-growing progeny, the modern-day broiler chicken. Because broiler breeders have the genetic potential to grow as quickly and efficiently as their broiler offspring, they must be severely feed restricted throughout the rearing period to ensure optimal health and avoid obesity (D’Eath et al., 2009). However, the severe quantitative feed restriction necessary for reproductive success results in chronic hunger and broiler breeders often display high levels of oral stereotypic behavior and aggression associated with hunger or frustrated feeding
©2014 Poultry Science Association Inc. Received December 11, 2013. Accepted February 25, 2014. 1 Corresponding author: [email protected]
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ABSTRACT In commercial production, broiler breeders are severely feed restricted to maintain healthy BW. This restriction can induce stereotypic behavior, including feather pecking, which has negative welfare implications for both the victim and performer. It has been suggested that the problem may be symptomatic of chronic hunger or the frustration of feeding motivation. In this study, we determined whether feather condition, as an indirect measure of feather pecking, could be improved via dietary manipulation. Six dietary treatments were tested, each with 5 replicate pens of 9 to 12 birds. Control diets (C) were fed on a daily or skip-a-day (SAD) basis. Alternative diets included soybean hulls as a bulking ingredient and calcium propionate (CaP) as an appetite suppressant of either a feed grade (F) or purified (P) quality. Both alternative diets were fed on either a daily or SAD basis. Five or 6 birds were randomly chosen from each pen and feather scored at 10, 14, 20, 26, and 36 wk of age.
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hens fed a qualitatively restricted diet compared with those fed a commercial quantitatively restricted diet in combination with alternative feeding schedules. In addition, differences between 2 qualities of CaP used in conjunction with high fiber diets were assessed. Feather condition scoring was used as an indicator for feather pecking behavior. Birds reared on diets associated with a reduction in hunger (i.e., qualitatively restrictive diets) were expected to perform less stereotypic pecking, including feather pecking, and therefore have better feather condition scores, and we hypothesized that the differences would be most apparent with using a purified quality of CaP. Because SAD feeding is generally considered to reduce welfare, it was hypothesized that the birds fed on a daily basis would be less hungry and would have better feather condition scores compared with their SAD-fed counterparts.
MATERIALS AND METHODS This experiment was performed in conjunction with Morrissey et al. (2014) using the same birds. All of the procedures used in this experiment were approved by the University of Guelph’s Animal Care Committee and were in accordance with the guidelines outlined by the Canadian Council for Animal Care.
Birds One-day-old Ross 708 broiler breeder females (n = 383) and males (n = 51) were donated (courtesy of Aviagen, via Horizon Poultry, Hanover, ON, Canada) for this experiment and reared at the OMAFRA Arkell Poultry Research Station (Guelph, ON, Canada). Males and females were reared separately. All of the birds were vaccinated against local diseases in accordance with the research farm’s vaccination protocol and reared according to the programs outlined by the breeding company (Aviagen, 2007). All birds were beak trimmed at 1 d of age at the hatchery using an infrared beam to minimize potential damage caused by feather pecking. In addition, the male chicks underwent routine spur removal at 1 d of age. For the first 3 d of life, birds were housed with a lighting regimen of 23L:1D at 20 lx. From then on the lighting schedule was as follows: 12L:12D (20 lx) from d 4 to 21, 8L:16D (4 to 7 lx) from d 22 to wk 22, 14L:10D (9 to 20 lx) from wk 22 to 24, 15L:9D (9 to 20 lx) from wk 24 to 26, and 16L:8D (9 to 20 lx) from wk 26 onward. Measured light intensity was 6.1 ± 1.6 lx in rearing and 15.0 ± 3.1 lx in lay. Rooms were heated to 32°C for the first 2 d and then gradually cooled to 21°C from 6 wk onward. Additionally, chicks were provided with a heated mat until 7 d of age. Upon arrival to the research farm, the female chicks were randomly allocated to 1 of 30 identical pens (1.83 × 2.36 m) that had been assigned 1 of 6 treatments. All of the pens had wood shavings (approximately 3 cm depth) covering the entire floor. Each pen was furnished with a wooden perch (0.05 × 0.05 × 1.52 m,
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(Dixon, 2008). Both types of feather pecking can reflect a negative state of well-being for both the performing and recipient birds. However, it is the severe type that can represent an economic loss to the industry (Lambton et al., 2010) because it is correlated with outbreaks of cannibalism (Leeson and Walsh, 2004; Dixon, 2008), decreased egg production, and increased morbidity and mortality (Mench, 2002). In addition, feather pecking is painful for the recipients and increases heat loss if large parts of the body become denuded, in turn increasing the cost of metabolic maintenance (Bilcik and Keeling, 1999; LaBrash and Scheideler, 2005). Although feather pecking appears to be a multifactorial problem caused by internal motivational states and external eliciting factors (Leeson and Walsh, 2004; Van Krimpen et al., 2005; Dixon, 2008), in broiler breeders, it may fall under the category of oral stereotypic behavior indicative of chronic hunger and frustrated feeding motivation. Researchers have attempted to alleviate chronic hunger and the associated symptoms in broiler breeder pullets using alternative diets (Savory and Larivière, 2000; Hocking et al., 2004; de Jong et al., 2005; Sandilands et al., 2006). To date, the most effective diets contain both a high-fiber component and a chemical compound (calcium propionate; CaP) acting as an appetite suppressant (Sandilands et al., 2005, 2006). There have been a wide range of behavioral benefits of these diets, with differences among experiments potentially associated with the quality of CaP (Savory and Larivière, 2000). Savory and Larivière (2000) were not able to reproduce the effects of a highly purified CaP (such as reduced symptoms of hunger and controlled growth rates; Savory et al., 1996) as effectively with an industrial or feed-grade chemical. Sandilands et al. (2006) were able to almost completely abolish the performance of object pecking in broiler breeders fed a diet containing a high-fiber component and CaP. However, most of the effective alternative diets have been fed on an ad libitum basis (Savory et al., 1996; Sandilands et al., 2005, 2006), which is not common practice in commercial production. It is common for North American broiler breeder producers to adopt alternative feeding schedules on which birds may not be fed every day (Bramwell et al., 2008). Skip-a-day (SAD) is the most commonly used alternative feeding schedule, where birds are fed twice their daily allocation every other day (Bramwell et al., 2008). Because the birds are not receiving feed on a daily basis, these alternative feeding regimens are considered to be detrimental to an animal’s well-being and are banned in the United Kingdom (DEFRA, 2007). There is some research describing feed efficiency and production in broiler breeders being fed using alternative feeding regimens (Bennett and Leeson, 1989; Ingram et al., 2001; de Beer and Coon, 2007). However, there was no research pertaining to the welfare implications of SAD feeding alone or in combination with alternative diets. The objectives of this experiment were to assess the differences in feather condition of broiler breeder
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FEATHER CONDITION IN BROILER BREEDER FEMALES
Table 1. Concentrations (g/kg) of soybean hulls (SBH) and calcium propionate (in feed-grade form, CaP-F, or purified form CaP-P) supplemented in treatment diets (C, commercial control; F, fiber and feed-grade CaP; P, fiber and purified CaP)1 Starter
Grower 1
Grower 2
Diet type
SBH
CaP-F
CaP-P
SBH
CaP-F
CaP-P
SBH
CaP-F
CaP-P
C F P
— 400 400
— 10 —
— — 10
— 400 400
— 30 —
— — 30
— 400 400
— 50 —
— — 50
1Inclusion levels of CaP increased with each period (starter 0 to 6 wk; grower 1, 6 to 12 wk; and grower 2, 12 to 22 wk). All treatments received a daily-fed commercial control diet after 22 wk as a layer crumble (not indicated here).
Experimental Protocol Prior to starting the experimental diets, birds were redistributed at 18 d of age and pens were standardized to an average weight as close to the overall mean as possible (308.72 ± 1.00 g/bird) by removing 1 or 2 birds/pen. This left 18 pens with 11 birds and 12 pens with 12 birds. At 20 wk, 22 of the smallest and least thrifty birds were culled (0, 1, or 2 birds/pen). During the rearing period (0 to 22 wk), 2 birds were found dead and 7 were euthanized due to injury, infection, sexing error, or beak deformities. During the laying period (22 to 37 wk), 2 birds were found dead and 15 were euthanized due to lameness and injury. Dietary Treatments. This experiment was a 3 × 2 factorial design, with 3 different diets and 2 feeding regimens. The 2 feeding regimens tested were daily feeding and SAD feeding, where birds received twice the daily allocation every other day. Alternate feeding regimens commenced once the birds reached 4 wk of age and birds were switched back to daily feeding at 22 wk. The 3 experimental diets tested were a commercial (C) diet, and 2 diets containing soybean hulls (SBH) and either a feed-grade quality (F) or purified (P) appetite suppressant (CaP; Table 1). Therefore, there were 2 treatment groups that were fed the same diet, with one fed daily and the other fed on a SAD basis, for all 3 diet types. A total of 4 rooms were used to house the birds
(12 pens/room total), with 2 rooms for daily birds and 2 rooms for SAD birds. To avoid disruption to birds not being fed while others were, daily and SAD birds were not housed in the same rooms, thereby confounding room with feeding frequency. One of the rooms housing the daily fed birds was also used to house the males used for this experiment (4 pens) and other females used for another experiment (4 pens). Therefore, one pen of each daily-fed diet types was housed in 3 of the last remaining 4 pens. In the other room housing daily-fed birds, 4 pens of each diet type were randomly distributed within the room. Two rooms were used to house the SAD birds; diet types as evenly distributed across rooms as possible, with 4 or 5 pens empty in each of the rooms. Diets that contained SBH and CaP were composed of a basal amount of the commercial crumble and were diluted with SBH (400 g/kg) and CaP (Table 1). As the birds matured, the inclusion rate of CaP increased; starter included 10 g of CaP/kg, grower 1 included 30 g of CaP/kg, and grower 2 included 50 g/kg. However, for the first 18 d, all birds were fed a commercial chick starter (2.86 Mcal/kg, CP = 18%, Table 2). All birds were fed daily following lights-on at 0800 h. Following breeder recommendations, all birds were fed on an ad libitum basis for the first week of life and then subsequently feed restricted from d 8 onward. All diets were formulated according to age of the bird: starter crumble from 0 to 6 wk, grower 1 crumble from 6 to 12 wk, grower 2 crumble from 12 to 22 wk, and layer crumble from 22 wk onward. The starter and grower diets were analyzed at Agri-Food Laboratories in Guelph, ON (Table 2). The layer diet was not analyzed; however, all birds were fed the same commercial layer crumble during the laying period. All treatments were fed the commercial starter diet from 1 to 19 d of age. On d 19, birds in the F and P treatments were switched from the commercial starter crumble to the alternative starter diet. Birds in these treatments were allocated a larger volume of feed due to the fibrous dilution and inclusion of CaP in the F and P diets. This increase depended on the age of the bird: 41, 43, and 45% more feed for starter, grower 1, and grower 2, respectively. At 22 wk of age, just before coming into lay, all birds were fed the commercial layer diet and SAD birds were switched to daily feeding. Data were collected until birds reached 36 wk of age.
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with top edges bevelled) at a height of 20 cm. Nest boxes (0.91 × 0.46 m, with 3 nest sites each measuring 0.30 m in width) were added at wk 20 to allow the birds to become accustomed before the onset of lay. Water was provided on an ad libitum basis from a nipple drinker (7 nipples/pen). Round pan feeders (38.1 cm in diameter) were used until the birds were 10 wk old. Hanging trough-style feeders (0.13 × 1.52 m) with exclusion grills were then installed to allow for more space per bird during feeding. At 22 wk, one rooster was added to each pen of hens to simulate commercial farm settings. Rooster feeders were installed before combining sexes and roosters were fed separately from the hens, following breeder guidelines. Birds were housed until they were 37 wk of age. Pens were cleaned out as needed; however, whenever dirty pens were cleaned out, all other pens received at least a top layer of fresh wood shavings.
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Table 2. Composition of C (commercial control), F [fiber and feed-grade calcium propionate (CaP)], and P (fiber and purified CaP) diets used in starter (S, 0 to 6 wk), grower 1 (G1, 6 to 12 wk), and grower 2 (G2, 12 to 22 wk) C Item
1Analyzed
P
S
G1
G2
S
G1
G2
S
G1
G2
60.6 8.8 24.0 3.14 2.0 0.34 1.0 0.12 — — 9.03 17.07 1.72 1.31 11.31 3.87 2.62 2,480
60.8 16.0 16.5 3.13 2.1 0.36 1.0 0.11 — — 9.98 15.65 1.93 1.62 11.17 3.28 2.43 2,480
60.8 16.0 16.5 3.13 2.1 0.36 1.0 0.11 — — 8.26 14.92 1.06 0.87 12.93 3.25 2.89 2,680
35.8 5.2 14.2 1.30 1.2 0.20 0.59 0.07 1.44 40.0 9.24 16.06 1.95 1.09 26.48 12.97 1.46 1,890
36.0 8.8 9.8 0.65 1.2 0.21 0.59 0.06 3.19 39.5 11.25 14.72 1.95 1.06 26.81 14.42 1.64 1,680
35.2 8.1 9.6 — 1.2 0.21 0.58 0.06 5.05 40.0 8.58 12.84 2.70 1.51 29.84 15.04 1.48 1,780
35.8 5.2 14.2 1.30 1.2 0.20 0.59 0.07 1.44 40.0 6.73 12.02 2.26 1.22 28.93 14.06 1.92 1,810
36.0 8.8 9.8 0.65 1.2 0.21 0.59 0.06 3.19 39.5 9.55 9.72 1.70 0.87 24.42 10.89 2.47 2,030
35.2 8.1 9.6 — 1.2 0.21 0.58 0.06 5.05 40.0 8.11 12.63 2.65 1.36 43.35 14.80 1.87 1,760
at Agri-Food Laboratories, Guelph, ON, Canada.
Feather Scoring. Feather scoring was performed when the birds were 10, 14, 20, 26, and 36 wk of age (only females scored). At each time point, 5 or 6 birds/ pen were randomly chosen, weighed, and then feather scored. Six body parts, including the neck, back, wings, legs, vent, and tail, were assessed and given a score from 0 to 5 (scoring system adapted from Bilcik and Keeling, 1999; LaBrash and Scheideler, 2005; Bright et al., 2006; Table 3). The highest (worst) possible total feather score for each bird was 30 (i.e., bird completely denuded including tissue damage).
Data Analysis The statistical analyses for this experiment were performed using the SAS statistical analysis package (SAS 9.2, 2007, SAS Institute Inc., Cary, NC). At each time point, the scores for all 6 body parts were summed for each bird and then averaged for each pen. A mixed model ANOVA with repeated measures was performed on pen means with age, diet type, and feeding frequency as the main factors. Room and room × feeding frequency were accounted for as random effects. Room × feeding frequency was included as a random effect
because feeding frequency was not randomized or evenly distributed across the 4 rooms. The analysis used for handling repeated measures over time was modeled after the method given by Wang and Goonewardene (2004), using a first order auto-correlation covariance structure. Data were +1 log-transformed to include scores of 0 and to normalize residuals before analyzing pen means. Orthogonal linear and quadratic contrasts were used to analyze differences in trends over time (rather than differences at specific ages) between diet types and frequencies. For contrasts involving diet type, overall means as well as trends across ages for C versus F + P and F versus P are reported.
RESULTS Feather scores throughout this experiment ranged from 0 to 14. Nine birds from the C treatment were the only birds with scores higher than 10. The highest score within the alternative diet treatments was 9 (daily F). There was a significant age effect because average feather damage increased with time (F4,71.1 = 33.37, P < 0.0001).
Table 3. Feather scoring scheme adapted from Bilcik and Keeling (1999), LaBrash and Scheideler (2005), Bright et al. (2006) Score
Description
0 1 2 3 4 5
Completely covered Slight damage: wet, broken feathers, up to 10% of feathers missing from a given area 10 to 50% of feathers missing from a given area (no blood or tissue damage) >50% of feathers missing from a given area (no blood or tissue damage) 10 to 50% of feathers missing from a given area including blood or tissue damage >50% of feathers missing from a given area including blood or tissue damage
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Ingredient Corn (%) Wheat shorts (%) Soybean meal (%) Limestone (%) Dicalcium phosphate (%) Salt (%) Vitamin-mineral premix (%) Methionine (%) CaP (%) Soybean hulls (%) Analyzed composition1 Moisture (%) CP (%) Ca:P ratio Calcium (%) NDF (%) Crude fiber (%) Fat (%) ME (kcal/kg)
F
FEATHER CONDITION IN BROILER BREEDER FEMALES
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Effect of Diet Type Overall, there was an effect of diet type (F2,16.2 = 8.90, P < 0.01). Orthogonal contrasts revealed a difference between the control diet and both alternative diets (F1,11 = 7.52, P = 0.019, Figure 1a) as well as a difference between the 2 alternative diets (F1,23.2 = 9.91, P < 0.01, Figure 1b). However, there was also an interaction of diet type with age (F8,52.3 = 3.35, P < 0.01, Figure 2a). The scores for all 3 diet types were similar at wk 10, but the C birds’ feather scores worsened much more quickly over time and were markedly worse at 36 wk compared with the F and P diets (Figure 2a).
Effect of Feeding Frequency There was no effect of feeding frequency on feather scores (F1,6.27 = 1.58, P = 0.25). There was, however, a significant interaction of frequency with age (F4,71.1 = 3.33, P = 0.015) with the daily-fed birds’ mean feather condition worsening more quickly over time than the
SAD-fed birds (Figure 2b). Both linear (F1,77.4 = 6.92, P = 0.010) and quadratic (F1,95.6 = 6.56, P = 0.012) trends differed over time between the daily and SAD feeding regimens.
DISCUSSION Feed restriction in broiler breeders is often associated with both stereotyped and aggressive pecking, 2 indicators of poor welfare. However, very little is known about the effect of alternative diets or feeding schedules on the feather condition of breeders during the rearing and production periods. In this experiment, all of the birds were relatively well-feathered (especially before the onset of lay). Very few birds showed any signs of tissue damage, with most of these cases resulting from bleeding feather follicles, not from direct pecking at the tissue. The birds used in this experiment were all beak trimmed and were housed in pens at low stocking densities on litter that was changed frequently, providing fresh substrate to support foraging and dustbathing. It
Figure 2. Effect of diet type (a) and feeding frequency (b) on mean feather scores (raw mean ± pooled SEM) from 10 to 36 wk of age. Trends over time differed between diet types (diet × age effect, P < 0.01), and frequencies (P = 0.015). Diet types include 1) commercial (C), 2) feed or industrial grade calcium propionate (CaP) + fiber (F), and 3) purified CaP + fiber (P). Feeding frequencies were either daily-fed or skip-a-day (SAD). Higher feather scores reflect worse feather condition; maximum score recorded was 14.
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Figure 1. Effect of diet type (raw mean ± pooled SEM) on mean feather score from 10 to 36 wk of age. Diet types include 1) commercial (C), 2) feed or industrial grade calcium propionate (CaP) + fiber (F), and 3) purified CaP + fiber (P). Contrasts uncovered significant differences, (a) C versus F + P, P = 0.019, and (b) F versus P, P < 0.01. Higher feather scores reflect worse feather condition; maximum score recorded was 14.
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Effect of Diet Type on Feather Condition From the data presented, it is clear that both alternative diet types (F and P) had a positive effect on feather condition. This finding supports our initial hypothesis, indicating a reduction in feather pecking from birds fed the alternative diets. However, it is impossible to determine whether the better feather condition is due to a decrease in pecking frequency, pecking severity, a combination of the 2, or something completely unrelated (i.e., feather damage associated with abrasions at the feeding trough). Dixon (2008) suggested that different motivational factors may influence the performance of gentle and severe pecking. Severe pecks were most similar in morphology to foraging pecks and may be caused by a lack of access to foraging substrates, whereas gentle pecking may be more closely related to preening behavior (Dixon, 2008). For the purpose of the current study, both gentle and severe feather pecking could be associated with chronic hunger because foraging is a component of feeding behavior and excessive preening or allo-preening could indicate redirected feeding frustration (Duncan and Wood-Gush, 1972). Therefore, a reduction in feeding frustration, or an increase in satiety would likely result in a reduction in both severe and gentle feather pecking. It seems, then, that both alternative diets (F and P) were effective at reducing hunger because feather damage increased more gradually in comparison with the feather condition of the birds reared on the C diet type. Behavior of these birds was recorded and reported elsewhere (Morrissey et al.,
2014); feather pecking was observed more frequently in the C treatments during rearing than both the F and P diets, with differences disappearing during the production period. No differences in feather pecking were observed between the 2 alternative diet types. The addition of fiber itself may have inherent effects on feather pecking and subsequent feather condition, without being directly hunger-related. There is some evidence that high-fiber diets have beneficial effects on laying hen welfare, where reaching satiety is not of concern because laying hens are generally fed ad libitum. Steenfeldt et al. (2007) reported a reduction in severe feather pecking and an improvement in feather condition at 53 wk of age for laying hens fed diets supplemented with silage or carrots compared with those fed a standard control diet. In addition, feather eating may serve as a means for increasing dietary fiber; Harlander-Matauschek et al. (2006a) showed that laying hens from a high feather pecking line worked significantly harder (i.e., pecked more at a key) for access to feathers, as well as wood shavings (although this difference was only numerical), than hens from a low feather pecking line. Feather eating increases the speed of food passage within the digestive tract, acting similarly to insoluble fibers, suggesting that a lack of sufficient dietary fiber increases the risk of feather pecking, especially for birds already prone to high levels of feather pecking (Harlander-Matauschek et al. 2006b). Previous studies including CaP within alternative diets for broiler breeders have used either a purified or industrial grade quality of the chemical (Savory et al., 1996; Savory and Larivière, 2000; Sandilands et al., 2005, 2006). However, Savory and Larivière (2000) suggested that the purified CaP used in a previous experiment (Savory et al., 1996) was more effective than the industrial grade version at both reducing symptoms of hunger and controlling growth rates when fed ad libitum. The results from the current study suggest that both grades of CaP were able to reduce hunger in comparison with the control diet, reflected by the improvement in feather condition. In fact, from 10 to 36 wk of age, average feather condition was better for birds fed the diet containing the industrial grade CaP (F). Based on the analyzed contents of each diet type (Table 2), it is possible that the differences in CP between the F and P diets were partly responsible for differences in feather condition. Ambrosen and Petersen (1997) demonstrated that laying hens fed diets with less than 15.2% CP had significantly worse plumage scores than those fed diets with 16.5 to 19.3% CP. The reason for this reduction in CP in the P diets is unclear and may be the result of an error during feed mixing at the feed mill. It is arguable that the better feather condition with both the F and P diets were not a result of a reduction in hunger, but rather of a reduction in general activity due to a feeling of malaise. The CaP has a very pungent smell and the birds may find it aversive (Buckley et al., 2011) or it may make them feel ill. Whereas Buckley et al. (2011) and Savory et al. (1996) found that birds had
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was also common practice at the research facility to apply pine tar to large denuded areas of the body to prevent further damage. These factors may have affected the level of feather pecking; however, there were still obvious and significant differences between treatments. Feather damage increased over time for all treatment groups. However, changes after 22 wk may have been the result of the addition of the roosters to the pens. Scores from the back and neck region may have specifically been influenced by the roosters, as broiler breeder males are vigorous during mating and can pull out feathers in the process (Millman et al., 2000). However, it was impossible to identify what degree of damage the roosters were responsible for, so all scores were included in the analyses. It is also necessary to note that all treatments were fed the same commercial diet from 22 wk onward. However, it can be assumed that differences in feather condition observed at 26 and 36 wk of age are indirectly related to dietary treatments as some carry-over effects from rearing have been previously demonstrated. Both Blokhuis and Van der Haar (1989) and Johnsen et al. (1998) found that rearing environments played a significant role in the development of feather pecking during the production period. In their experiments, chicks reared on wire feather pecked more later in life than chicks that had been reared with access to a foraging and dustbathing substrate.
FEATHER CONDITION IN BROILER BREEDER FEMALES
a slight preference for a control diet over a diet including CaP, this preference was not exclusive and birds still consumed the alternative diet.
Effect of Feeding Frequency on Feather Condition
Conclusions The results of this experiment supported our first hypothesis that high-fiber diets including an appetite suppressant would improve feather condition; however, the industrial grade CaP resulted in better feather condition than the purified chemical. Similar diets in previous research have been shown to reduce hunger and feeding motivation compared with commercially restricted birds. Therefore, it appears that a reduction in feather damage represents a reduction in hunger. The F diet was the most effective at improving feather
condition, indicating that it may have been most effective at reducing hunger. Interestingly, our hypothesis that SAD feeding would result in poorer feather condition scores and would therefore negatively affect welfare proved incorrect. The SAD feeding actually delayed the decrease in feather condition over time. The feather scores of the dailyfed birds worsened at a quicker rate, suggesting that SAD birds grew accustomed to their feeding schedule over time and learned when to expect feed. On “onfeed” days, they may have been receiving enough feed to satisfy their hunger. The ability to reach satiety every other day may be more welfare friendly than never feeling full on a daily feeding schedule. Not only does better feather condition suggest that birds on alternative diets are experiencing different levels of satiety, but increased feather cover can also act to protect the hens against tissue damage and subsequent infection during mating in the production period.
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Feather condition worsened more quickly for birds that were fed daily compared with their SAD counterparts, particularly while the birds remained on different feeding frequencies (through 22 wk). Thereafter, SAD birds continued to have better feather condition than daily-fed birds, although all birds’ feather condition deteriorated at similar rates. Feather pecking behavior in the morning immediately following feeding did not differ between daily-fed and SAD-fed birds (Morrissey et al., 2014). The lack of difference in feather pecking behavior suggests that not all occurrences of feather pecking were observed or that daily-fed birds were performing more severe feather pecking, rather than gentle feather pecking. The differences in feather condition between daily and SAD birds did not support our original hypothesis that SAD-birds would show more severe symptoms of chronic hunger and therefore have worse feather condition. The difference in trends over time between the feeding frequencies may reflect the time it took for the birds to become accustomed to the SAD feeding schedule. As the birds grew accustomed to the SAD regimen, it is possible that they were reaching a higher level of satiety during “on-feed” days than daily feedings could allow. In an experiment with feedrestricted sows, Douglas et al. (1998) was able to demonstrate that interval feeding (once every 3 d) increased physiological parameters of satiety and reduced behavioral indicators of feeding frustration. For example, interval-fed sows had a more pronounced increase in blood glucose and cholecystokinin than their daily-fed counterparts (Douglas et al., 1998). Cholecystokinin is thought to be related to satiety because it has been implicated in the termination of feeding (Douglas et al., 1998; Moran et al., 1998). In addition, interval-fed sows were more inactive, drank less water, and performed less sham chewing than daily-fed sows (Douglas et al., 1998).
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Douglas, M. W., J. E. Cunnick, J. C. Pekas, D. R. Zimmerman, and E. H. von Borell. 1998. Impact of feeding regimen on behavioral and physiological indicators for feeding motivation and satiety, immune function, and performance of gestating sows. J. Anim. Sci. 76:2589–2595. Duncan, I. J. H., and D. G. Wood-Gush. 1972. Thwarting of feeding behaviour in the domestic fowl. Anim. Behav. 20:444–451. Guy, J. 2001. Environmental enrichment for broilers—Will it prevent feather pecking? World Poult. 17:22–23. Harlander-Matauschek, A., C. Baes, and W. Bessei. 2006a. The demand of laying hens for feathers and wood shavings. Appl. Anim. Behav. Sci. 101:102–110. Harlander-Matauschek, A., H. P. Peipho, and W. Bessei. 2006b. The effect of feather eating on feed passage in laying hens. Poult. Sci. 85:21–25. Hocking, P. M., and E. K. M. Jones. 2006. On-farm assessment of environmental enrichment for broiler breeders. Br. Poult. Sci. 47:418–425. Hocking, P. M., V. Zaczek, E. K. M. Jones, and M. G. Macleod. 2004. Different concentrations and sources of dietary fibre may improve the welfare of female broiler breeders. Br. Poult. Sci. 45:9–19. Ingram, D. R., L. F. Hatten, and B. N. McPherson. 2001. Effects of initiation age of skip-a-day feed restriction on skeletal development in broiler breeder males. J. Appl. Poult. Res. 10:16–20. Johnsen, P. F., K. S. Vestergaard, and G. Nørgaard–Neilsen. 1998. Influence of early rearing conditions on the development of feather pecking and cannibalism in domestic fowl. Appl. Anim. Behav. Sci. 60:25–41. LaBrash, L. F., and S. E. Scheideler. 2005. Farm feather condition score survey of commercial laying hens. J. Appl. Poult. Res. 14:740–744. Lambton, S. L., T. G. Knowles, C. Yorke, and C. J. Nicol. 2010. The risk factors affecting the development of gentle and severe feather pecking in loose housed laying hens. Appl. Anim. Behav. Sci. 123:32–42. Leeson, S., and T. Walsh. 2004. Feathering in commercial poultry. II. Factors influencing feather growth and feather loss. World’s Poult. Sci. J. 60:52–63.
