Laura M. Dixon a & Ian J. H. Duncan a a Department of Animal and Poultry Science,

Transcription

1 This article was downloaded by: [Dr Kenneth Shapiro] On: 09 June 2015, At: 08:29 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Journal of Applied Animal Welfare Science Publication details, including instructions for authors and subscription information: Changes in Substrate Access Did Not Affect Early Feather- Pecking Behavior in Two Strains of Laying Hen Chicks Laura M. Dixon a & Ian J. H. Duncan a a Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada Published online: 16 Dec To cite this article: Laura M. Dixon & Ian J. H. Duncan (2010) Changes in Substrate Access Did Not Affect Early Feather-Pecking Behavior in Two Strains of Laying Hen Chicks, Journal of Applied Animal Welfare Science, 13:1, 1-14, DOI: / To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the Content ) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or

2 indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at

3 JOURNAL OF APPLIED ANIMAL WELFARE SCIENCE, 13:1 14, 2010 Copyright Taylor & Francis Group, LLC ISSN: print/ online DOI: / ARTICLES Changes in Substrate Access Did Not Affect Early Feather-Pecking Behavior in Two Strains of Laying Hen Chicks Laura M. Dixon and Ian J. H. Duncan Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada Feather pecking, commonly found in flocks of laying hens (Gallus gallus), is detrimental to bird welfare. Thought to cause this problem is the normal housing of layers without a floor substrate. Some evidence suggests that early substrate access decreases later feather pecking. However, there has been little research on the immediate effects of a change in substrate availability on bird welfare, although environmental modifications like this are often done when brooding and rearing laying hen chicks. To investigate this, the behavior of two strains of laying hen chicks was recorded for 4 weeks. The study kept the birds on either wire or peat moss for 14 days and then switched half the chicks to the other flooring. Early feather pecking was not significantly different for birds started on peat moss and switched to wire than for birds only on wire (p >.05). Because moving chicks from peat moss to wire did not cause additional welfare problems, the study recommends that chicks be kept on a substrate when young as feather-pecking levels are lower and immediate welfare is improved compared with birds kept only on wire. Abnormal behavior patterns are prevalently found in smaller, barren environments and may indicate poor welfare (Mason, 1991) as they are generally detri- Correspondence should be sent to Laura M. Dixon, Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario N1G 2W1, Canada. ldixon@uoguelph.ca 1

4 2 DIXON AND DUNCAN mental to the nonhuman animal or to the group in which the animal is kept (Garner, 2005). An abnormal behavior commonly found in the laying-hen (Gallus gallus) industry is feather pecking, the destruction or removal of feathers or down feathers of one bird by another (Hoffmeyer, 1969), with feather removal being painful for the recipient bird (Gentle & Hunter, 1990). The severity of feather pecking increases as the birds age (Newberry, Keeling, Estevez, & Bilcik, 2007) and potentially can progress to cannibalism, in which living tissue is pecked and consumed (Perry & Allen, 1976). Feather pecking is an extensive problem as it can be found from Day 1 of life (Chow & Hogan, 2005; Jensen, Palme, & Forkman, 2006; Savory & Mann, 1999); by 14 weeks, 77% of commercial flocks surveyed were found to have some feather pecking (Huber-Eicher & Sebo, 2001). This study deals with the feather pecking shown early in life, which is generally less severe than that found in older birds. In general, feather pecking is thought to stem from frustrated motivations either to dustbathe or forage, and this is induced by the lack of an appropriate substrate on which to perform these behaviors (Blokhuis 1986, 1989; Vestergaard, Kruijt, & Hogan, 1993). There is much evidence that providing a substrate (sand, straw, and wood shavings) will decrease the amount of feather pecking when compared with feather pecking in birds kept without a substrate (Blokhuis & Arkes, 1984; Huber-Eicher & Wechsler, 1997; Nicol et al., 2001). Studies agree that the current environment on which the bird is housed is important (Huber-Eicher & Audige, 1999; Nicol et al., 2001; however, as different studies have found different results, the effects of early experience with a substrate on later behavior are still disputed. Vestergaard et al. (1993) found early substrate experience to be protective against later feather pecking, whereas Huber- Eicher and Wechsler (1997) and Newberry et al. (2007) did not. Past studies focused mainly on the effect of early experience on behavior later in life and did not examine any immediate consequences of changing environments on abnormal behavior. Laying hens are often switched between environments with and without substrates after hatching, brooding, or rearing; after hatching, chicks may be moved to a brooder with wood shavings, then switched to wire cages 3 weeks later until point of lay (Sainsbury, 2000). Because these environment switches are recommended industry practice (Gillespie, 2004; North & Bell, 1990), it is important to know if there are any immediate consequences for bird welfare. Feather pecking also has a genetic component (Cuthbertson, 1980), and levels of feather pecking have been studied in a number of poultry strains. However, many tend to be dual purpose (selected for meat and eggs) or Red Junglefowl (ancestor of domestic fowl) and thus are not commonly used as commercial eggproduction strains (Hughes & Duncan, 1972; Savory & Mann, 1999; Vestergaard et al., 1993). There has been work done using commercial strains to estimate feather-pecking heritability; however, these studies focused more on feather-

5 FEATHER-PECKING BEHAVIOR 3 pecking heritability among different ages of birds (Kjaer & Sorensen, 1997) or used lines differing in feather-pecking behavior (high and low feather-pecking lines) to determine other behavioral differences (Rodenburg & Koene, 2003) and did not focus on the effects of certain early experiences on different commercial strains. It is possible that different strains may respond differently to the addition or removal of substrates, and a line better suited to these production practices could be found. The objectives of this study were threefold: (a) to test what effect early experience with or without a preferred natural substrate (peat moss) would have on immediate bird welfare, (b) to investigate the effects of early environment (with or without a substrate) on feather pecking in the current environment (with or without a substrate), and (c) to examine the difference in feather-pecking behavior early in life between two commonly used strains of egg-laying chicks in these different environments. We tested the hypothesis that high levels of feather pecking are the result of improper early experience without a loose substrate. We predicted that early experience with peat moss (a much-preferred dustbathing substrate) in Weeks 1 and 2 of life would decrease feather pecking in Weeks 3 and 4 of life. These birds, compared with wire-reared birds and birds with appropriate early experience of peat moss during Weeks 1 and 2 then switched to wire (change of environment) for Weeks 3 and 4, should feather peck less than birds reared and housed on wire (no change of environment). We also hypothesized that different strains of birds will feather peck different amounts due to the genetic component of feather pecking and predicted that Institut de Sélection Animale (ISA) White Leghorns will feather peck more than ISA Brown Leghorns. Animals METHODS Day-old female ISA White Leghorns (white egg layers) and ISA Brown Leghorns (brown egg layers) were obtained from a local hatchery (Bonnie s Hatchery, Elmira, Ontario). Chicks were not beak-trimmed to make featherpecking damage more obvious. Chicks were randomly distributed throughout the pens: 12 birds per pen, 576 birds per strain in total. Strains of chicks were kept separate throughout the experiment. Power tests were performed before beginning this experiment using estimates from previous experiments (Blokhuis & Arkes, 1984; Johnsen, Vestergaard, & Norgaard-Nielsen, 1998) that compared feather pecking on wire- and substratereared birds. A sample size of n D 48 per treatment (wire or peat moss flooring), at a power D 90% and D 0.05, was needed to detect a 30% difference between the treatment averages; the level is equal, or superior to, that of previous work.

6 4 DIXON AND DUNCAN Housing The chicks were kept in wooden frame floor pens measuring 127 cm 107 cm 60 cm with sides of 2.5 cm 2.5 cm grid chicken wire. Half the pens had 1 cm 1 cm grid wire flooring, and half had solid floors covered with approximately 2 in. of peat moss. The sides of the pens were covered with black cloth, so chicks could not see into other pens. The chicks were fed ad libitum chick starter crumbles (Protein 20%, ME 1290 kcal/lb) and water from automatic cup drinkers. The feed was sifted before being fed to the chicks to remove as much dust as possible and to discourage dustbathing at the feeder. Lights were left on 24 hr a day for the first 3 days and then reduced to a 10L:14D schedule. The temperature started at 34 ı C and was reduced to 28 ı C over the 4 weeks of the trial. Observations Observations of the chicks were conducted from 1 to 4 weeks of age. This was divided into two periods. Period One covered Weeks 1 and 2 of life, and Period Two covered Weeks 3 and 4 of life. Both live and video observations were performed and statistically compared to show no significant difference between the two methods (p >.05). A 20-min observation session was performed twice weekly on each pen. During the 20-min observation session, all-occurrence sampling and focal animal sampling were used. Each pen was divided into six equal-size, unmarked sections and a table of random numbers was used to determine which section to observe. The chick closest to the center of that section was observed. If there was no chick in this section, the next numerical section was used until a chick was found. The focal animal was switched every minute, for a total of 20 animals per session; it was possible for a bird to be observed more than once in an observation session. For Period One, there were 12 chicks in each pen. At the end of this period, we used a plastic board to split each pen in two; this was also a novel environmental stimulus that all birds experienced. At this point, 6 chicks from each pen remained in that pen, whereas the other 6 were moved to a pen in the other treatment. For example, with a wire pen, 6 birds remained in the wire-floor treatment, and 6 birds were removed and placed in a peat moss pen. These birds were not mixed with the other treatment birds. The 6 birds moved remained as a group and were placed in an empty half of a peat moss pen. Birds who did not switch treatments were handled and then returned to their own pens with the original flooring. This resulted in four treatments of birds: 1. Birds who had originally been on wire and were kept on wire (P1P2 Wire), 2. Birds who were originally on peat moss and were kept on peat moss (P1P2 Peat Moss),

7 FEATHER-PECKING BEHAVIOR 5 3. Birds who were on wire and were switched to peat moss (P1 Wire P2 Peat Moss), and 4. birds who were on peat moss and switched to wire (P1 Peat Moss P2 Wire). Behavioral Measures The following behavior patterns were recorded: 1. Dustbathing: chicks squatting on the ground, kicking their legs, rubbing their head and side on the ground, and performing a vertical wing shake. Chickens will perform these same movements when vacuum dustbathing on wire (Vestergaard, 1982a); 2. Feather pecking: destruction or removal of feathers or down feathers from one bird by the pecking of another bird; 3. Ground scratching: chick scratching the ground with one leg at a time, alternating between legs; and 4. Ground pecking: chick directing a peck at the ground or particles on the ground. A behavior pattern was considered to last until there was a 4-s or longer pause in the performance of the behavior. At this point, the next behavior the focal animal performs was recorded. Ethical Note The University of Guelph Animal Care Committee, which adheres to Canadian Council on Animal Care guidelines, approved the use of all animals and methods in the following experiments. The birds used in this study were not beak-trimmed; to prevent potential cannibalism, the birds were inspected a minimum of three times a day (once at 8 a.m., once at 12 p.m., and once at 4 p.m.). Any feather-pecking injuries found were coated in pine tar to discourage further pecking, and the bird was checked once an hour for the rest of the light period to ensure the injury did not get worse. If the pine tar was unsuccessful in discouraging pecking, the bird would be removed from the pen; however, this measure was not needed in this study. Statistical Analysis A mixed model variance-component analysis was used to determine the effect of pen floor type (wire or peat moss) and previous experience with a floor type

8 6 DIXON AND DUNCAN on chick behavior (SAS, Version 8). The model had Strain as a blocking factor, Pen nested in Trial as a random factor, and all interaction terms between the independent variables were included. Data were normalized with a p (x C 0.375) transformation. Differences of the Least Square Means adjusted by Tukey were used to determine treatment differences. RESULTS Feather Pecking Period One (P1). In the first 2 weeks of life, all chicks kept on wire feather pecked more than chicks kept on peat moss (F.1;40/ D 44.2, p <.0001), although these levels were quite low (3 pecks/30 min for wire housed, 1 peck/30 min for peat moss housed; Table 1). ISA Whites feather pecked more overall than ISA Browns in Period One (Strain: F.1;40/ D 11.07, p D.0019; Table 2). There was no interaction between strain (WL and ISAB) and treatment (wire or peat moss, (F.1;40/ D 0.07, p D.7869). Period Two (P2). Again, for both ISA White and ISA Brown chicks, those who were on wire feather pecked more than those on peat moss (6 pecks/30 min vs. 2 pecks/30 min), regardless of early experience with a substrate; thus, chicks housed on peat moss then switched to wire did not feather peck significantly less from those only on wire (F.3;80/ D 38.09, p <.0001; Table 1). ISA White chicks feather pecked more overall than ISA Brown chicks (F.1;80/ D 70.62, p <.0001; Table 2), and there was no significant interaction found between these factors (F.3;80/ D 2.22, p D.0913). Dustbathing All birds dustbathed at the same frequency throughout the trial, regardless of their previous experience (F.1;40/ D 6.46, p D.0948) or the environment on which they were currently being housed (F.3;80/ D 1.53, p D.2133; Table 1). There was no difference in the amount of dustbathing performed by ISA Brown and ISA White chicks (P1: F.1;40/ D 0.01, p D.9034; P2: F.1;80/ D 2.89, p D.0884; Table 2), nor were there any interactions of treatment and strain (P1: Trt*Strain: F.1;40/ D 0.02, p D.9010; P2: Trt*Strain: F.3;80/ D 1.34, p D.2676). Ground Pecking and Scratching Period One (P1). Both ISA White and ISA Brown chicks housed on peat moss performed more ground pecking and scratching than those on wire floor

9 TABLE 1 The Average Frequencies of Feather Pecking, Dustbathing, and Ground Pecking and Scratching on Wire and Peat Moss Floor Treatments for Period One (A) and Period Two (B) A) Period One Peat Moss (M SE) Wire (M SE) F(df ) P Value Feather Pecking F(1, 40) D 44.2 <.0001* Dustbathing F(1, 40) D Ground Pecking and Scratching F(1, 42) D <.0001* B) Period Two Peat Moss Only (M SE) Wire Then Peat Moss (M SE) Peat Moss Then Wire (M SE) Wire Only (M SE) F(df ) P Value Feather Pecking F(3, 80) D <.0001 Dustbathing F(3, 80) D Ground Pecking and Scratching F(3, 80) D <.0001 *denotes a significant difference between treatments. 7

10 8 DIXON AND DUNCAN (A) TABLE 2 The Average Frequencies of Feather Pecking, Dustbathing, and Ground Pecking and Scratching for ISA White Leghorns and ISA Brown Leghorns During Period One (A) and Period Two (B) Period One WL (M SE) ISAB (M SE) F(df ) P Value Feather Pecking F(1, 40) D * Dustbathing F(1, 40) D Ground Pecking and Scratching F(1, 40) D * (B) Period Two WL (M SE) ISAB (M SE) F(df ) P Value Feather Pecking F(1, 80) D <.0001* Dustbathing F(1, 80) D Ground Pecking and Scratching F(1, 80) D *denotes a significant difference between treatments. (F.1;40/ D , p <.0001; Table 1). ISA Brown chicks had a higher overall frequency of these behavior patterns than White Leghorns (F.1;40/ D 12.67, p D.002; Table 2); however, there was no significant interaction (F.1;40/ D 0.01, p D.9078). Period Two (P2). Regardless of previous floor type, both strains of birds ground pecked and scratched more when kept on peat moss than when kept on wire floor (F.3;80/ D , p <.0001; Table 1). There were also no differences in the ground pecking and scratching between strains of birds on their current floor types (F.1;80/ D 0.69, p D.409; Table 2) and no significant interactions of these factors (F.3;80/ D 3.1, p D.0911). DISCUSSION The presence of peat moss decreased the amount of feather pecking regardless of the chicks early experience with it. The prediction that early experience (during Weeks 1 and 2 of life) with a substrate would decrease feather pecking behavior after substrate removal (during Weeks 3 and 4 of life) was not met. This was

11 FEATHER-PECKING BEHAVIOR 9 not a Type II error; with this sample size (n D 48 pens per treatment per strain), we can say with confidence that there cannot have been an effect larger than a 30% difference between the means. Chicks are thought to show preferences for dustbathing on, or pecking and scratching at, a particular substrate around 8 to 10 days of life (Sanotra, Vestergaard, Agger, & Lawson, 1995; Vestergaard, 1982b). In this experiment, chicks were kept on their original floor treatment for the first 14 days of life, giving them time to develop preferences for either the peat moss or the feathers of other birds as dustbathing substrates or forages. These findings do not fit the hypothesis that the feather pecking shown early in life stems from lack of early experience with a substrate. Instead, only the current environment had an impact on feather pecking in the first few weeks after the environment was changed. There has been extensive research done on the importance of early life experiences on later behavior (Renner & Rosenweig, 1987). In laying hens, it has been demonstrated that early experience with an appropriate substrate protects against later feather pecking (Johnsen et al., 1998; Vestergaard, 1994). For example, birds who were reared only on straw feather pecked more than those reared on sand C peat, even after all were switched to straw alone (Norgaard-Nielsen, Vestergaard, & Simonsen, 1993). There are, however, instances where the current environment has a greater influence on behavior than previous experience (Nicol et al., 2001). For example, some studies on feather pecking only found an effect of current environment: Early access to litter did not reduce the later rates of feather pecking in commercial flocks of free-run poultry (Gunnarsson, Keeling, & Svedberg, 1999). Sand, which was protective in some studies, did not prevent injurious feather pecking when chicks were kept on it from Day 1 of life; however, chicks kept with sand and straw did not develop this problem (Huber-Eicher & Wechsler, 1997). More recently, Newberry et al. (2007) did not find any association on an individual bird basis between low levels of early foraging behavior on a substrate and adult feather-pecking behavior; in fact, birds who foraged more when young were more likely to perform severe feather pecks when older. A reason for the lack of protective effects from early substrate experience in this study may be that the observations ended after the 4th week of life, whereas in other experiments they ended later in life, even after birds came into lay. As birds age, other factors, such as hormone surges before lay, may influence their feather pecking (Hughes, 1973). Although birds have been shown to feather peck early in life and this feather pecking is affected by the presence of a substrate (Jensen et al., 2006; Nicol et al., 2001; Savory & Mann, 1999), the protection from early substrate experience may not be shown until the birds are older, so 3- to 4-week-old chicks may not exhibit any benefit of early substrate experience, but perhaps older birds would.

12 10 DIXON AND DUNCAN Further work examining the effects of early experience, with and without a substrate, on feather-pecking behavior throughout a bird s life will help clear up this disagreement. In addition, the quality of the enrichment may influence how effective it will be in preventing abnormal behaviors a chewing toy did not decrease tail biting in pigs but straw did (Van de Weerd, Docking, Day, & Edwards, 2005). For chickens, the quality of the enrichment also influences the amount of time spent interacting with it, with higher quality stimuli having more interactions (Huber-Eicher & Wechsler, 1998). The peat moss provided to the birds in this experiment is a preferred substrate for pecking and scratching (Petherick & Duncan, 1989); it may have been more effective at preventing feather pecking than some of the substrates used in other experiments (straw, sand, wood shavings). Finally, the lack of protection from early substrate experience may be the result of half the chicks being moved to a new environment whereas others remained in their original pens. It is possible that the experience of a novel environment superseded any beneficial early experience. However, we feel this is unlikely; at the point in the experiment when half the chicks were moved, all pens were divided by a plastic board. This divider would be novel for all birds and would change the look and the size of the environment in both the original and new pens. Furthermore, birds, given the opportunity to interact with novelty, perform less feather pecking than birds who did not interact (Chow & Hogan, 2005). Thus, the birds moved to the novel environments should have shown less feather pecking compared with those who did not move (birds moved from wire to peat moss should have feather pecked less than birds who did not move and were kept only on peat moss), but this was not the case. It was the current environment that influenced the amount of feather pecking performed, at least early in life. Although the exact benefits of being reared with a substrate are not clear, the provision of a substrate does decrease feather pecking; the short-term consequences of changing environments do not exacerbate this behavior. It appears that the most reliable way to have low feather-pecking rates in a flock is to provide some form of substrate with enough room for the birds to interact with it in a natural way. Feather pecking is an abnormal behavior that indicates a pathological condition like stress (Fox, 1968). Not only are the consequences of feather pecking harmful but also the performance of this behavior alone indicates a problem with how chickens are being kept. The results found here add to the evidence that continued research is needed to develop enriched cages or floor systems that improve poultry welfare. In this experiment, current environment influenced ground pecking and scratching, with birds housed on a substrate performing significantly more pecking and scratching at the peat moss than birds reared on wire, regardless of early substrate experience. However, the number of dustbathing bouts remained similar between

13 FEATHER-PECKING BEHAVIOR 11 treatments (peat moss and wire); there was no effect of early experience with or without a substrate. Similar to ground pecking and scratching, the amount of feather pecking was also affected by provision of a substrate, with birds on wire feather pecking more than those on peat moss; again, there was no effect of early experience. This complements the existing evidence of a relationship between feather pecking and pecking and scratching at a substrate. Because the numbers of dustbathing bouts were not affected by the presence of a substrate, whereas ground pecking and scratching and feather pecking were, it appears that dustbathing motivation is not associated with feather pecking. Dustbathing is not a time-consuming behavior pattern (about 1 hr every other day; Vestergaard, a), whereas foraging occupies about 67% of the daily time budget (Dawkins, 1989). Because higher quality substrates, like peat moss, elicit more pecking and scratching (Huber-Eicher & Wechsler, 1998), there is not much extra time for birds to develop abnormal behavior. However, this was count data and not durations, so it may not tell the whole story. Examining the daily time budgets of chicks and determining how much time is spent performing various behavior patterns (dustbathing, foraging, and feather pecking) in various environments (barren, with substrates) would help confirm this idea. Because of the difficulties in determining the difference between dustbathing and foraging pecks (both of which are directed at the ground and look similar), a different technique may need to be developed to differentiate between the two and determine how much time is actually spent doing each activity. There was a strain difference in the amount of feather pecking performed between the ISA Whites and ISA Browns, with ISA Whites feather pecking more than twice as much as ISA Browns. By the end of the trial, there were no strain differences in the amount of dustbathing or ground pecking and scratching. Feather pecking has a heritable component (Cuthbertson, 1980; Kjaer & Sorensen, 1997); because ISA Browns show significantly less feather pecking than ISA Whites during early life, their use could be encouraged; they could potentially be crossed with higher feather-pecking strains to reduce overall levels performed. CONCLUSION Our results contradict the hypothesis that feather pecking early in life stems from lack of early experience with a substrate. Early experience with the substrate during the first 2 weeks of life did not protect the birds from feather pecking during Weeks 3 and 4; it was the current environment that influenced the amount of feather pecking performed. However, there were no negative consequences

14 12 DIXON AND DUNCAN found by housing the birds with a substrate early in life and switching them to a more barren environment (wire) other than those already found in wirehoused birds. As birds have better welfare when kept with a substrate, this practice is recommended. In addition, ISA Brown Leghorns perform overall less feather pecking in the first 4 weeks of life than ISA White Leghorns, and their increased use should be encouraged both in industry and research. Finally, these results emphasize the need for enriched cages or pens and indicate that the ability to forage may be more important in preventing feather pecking than dustbathing. However, due to the similarity of dustbathing and foraging pecks, new techniques are needed to determine definitively if the motivation behind feather pecking relates to foraging or dustbathing. ACKNOWLEDGMENTS This research was supported by a grant from the Ontario Ministry of Agriculture, Food and Rural Affairs and from the Natural Sciences and Engineering Research Council of Canada. We also thank Georgia Mason for her help and comments on the article. REFERENCES Blokhuis, H. J. (1986). Feather-pecking in poultry: Its relation to ground-pecking. Applied Animal Behaviour Science, 16, Blokhuis, H. J. (1989). The effect of a sudden change in floor type on pecking behavior in chicks. Applied Animal Behaviour Science, 22, Blokhuis, H. J., & Arkes, J. G. (1984). Some observations on the development of feather-pecking in poultry. Applied Animal Behaviour Science, 12, Chow, A., & Hogan, J. A. (2005). The development of feather pecking in Burmese red junglefowl: The influence of early experience with exploratory-rich environments. Applied Animal Behaviour Science, 93, Cuthbertson, G. J. (1980). Genetic variation in feather-pecking behaviour. British Poultry Science, 21, Dawkins, M. S. (1989). Time budgets in red junglefowl as a baseline for the assessment of welfare in domestic fowl. Applied Animal Behaviour Science, 24, Fox, M. W. (1968). Abnormal behaviour in animals. Toronto, Ontario, Canada: W. B. Saunders Company. Garner, J. P. (2005). Stereotypies and other abnormal repetitive behaviors: Potential impact on validity, reliability, and replicability of scientific outcomes. ILAR Journal, 46, Gentle, M. J., & Hunter, L. N. (1990). Physiological and behavioural responses associated with feather removal in Gallus gallus var domesticus. Research in Veterinary Science, 50, Gillespie, J. R. (2004). Modern livestock & poultry production (7th ed.). Clifton Park, NY: Delmar Learning.

15 FEATHER-PECKING BEHAVIOR 13 Gunnarsson, S., Keeling, L. J., & Svedberg, J. (1999). Effect of rearing factors on the prevalence of floor eggs, cloacal cannibalism and feather pecking in commercial flocks of loose housed laying hens. British Poultry Science, 40, Hoffmeyer, I. (1969). Feather pecking in pheasants: An ethological approach to the problem. Danish Review of Game Biology, 6, Huber-Eicher, B., & Audige, L. (1999). Analysis of risk factors for the occurrence of feather pecking in laying hen growers. British Poultry Science, 40, Huber-Eicher, B., & Sebo, F. (2001). The prevalence of feather pecking and development in commercial flocks of laying hens. Applied Animal Behaviour Science, 4, Huber-Eicher, B., & Wechsler, B. (1997). Feather pecking in domestic chicks: Its relation to dustbathing and foraging. Animal Behaviour, 54, Huber-Eicher, B., & Wechsler, B. (1998). The effect of quality and availability of foraging materials on feather pecking in laying hen chicks. Animal Behaviour, 55, Hughes, B. O. (1973). The effect of implanted gonadal hormones on feather pecking and cannibalism in pullets. British Poultry Science, 14, Hughes, B. O., & Duncan, I. J. H. (1972). The influence of strain and environmental factors upon feather pecking and cannibalism in fowls. British Poultry Science, 13, Jensen, A. B., Palme, R., & Forkman, B. (2006). Effect of brooders on feather pecking and cannibalism in domestic fowl (Gallus gallus domesticus). Applied Animal Behaviour Science, 99, Johnsen, P. F., Vestergaard, K. S., & Norgaard-Nielsen, G. (1998). Influence of early rearing conditions on the development of feather pecking and cannibalism in domestic fowl. Applied Animal Behaviour Science, 60, Kjaer, J. B., & Sorensen, P. (1997). Feather pecking behaviour in White Leghorns, a genetic study. British Poultry Science, 38, Mason, G. J. (1991). Stereotypies: A critical review. Animal Behaviour, 41, Newberry, R. C., Keeling, L. J., Estevez, I., & Bilcik, B. (2007). Behaviour when young as a predictor of severe feather pecking in adult laying hens: The redirected foraging hypothesis revisited. Applied Animal Behaviour Science, 107, Nicol, C. J., Lindberg, A. C., Phillips, A. J., Pope, S. J., Wilkins, L. J., & Green, L. E. (2001). Influence of prior exposure to wood shavings on feather pecking, dustbathing and foraging in adult laying hens. Applied Animal Behaviour Science, 73, Norgaard-Nielsen, G., Vestergaard, K. S., & Simonsen, H. B. (1993). Effects of early experience and stimulus enrichment on feather damage in laying hens. Applied Animal Behaviour Science, 38, North, M., & Bell, D. (1990). Commercial chicken production manual. Westport, CT: AVI Publishing Company. Perry, G. C., & Allen, J. (1976). The effects of caging conditions on the incidence of feather pecking and cannibalism. In 5th European Poultry Conference (pp ). Malta: World Poultry Science Association. Petherick, J. C., & Duncan, I. J. H. (1989). Behaviour of young domestic fowl directed towards different substrates. British Poultry Science, 30, Renner, M. J., & Rosenzweig, M. R. (1987). Enriched and impoverished environments: Effects on brain and behavior. New York: Springer. Rodenburg, T. B., & Koene, P. (2003). Comparison of individual and social feather pecking tests in two lines of laying hens at ten different ages. Applied Animal Behaviour Science, 81, Sainsbury, D. (2000). Poultry health and management (4th ed.). Ames, IA: Blackwell. Sanotra, G. S., Vestergaard, K. S., Agger, J. F., & Lawson, L. G. (1995). The relative preferences for feathers, straw, wood-shavings and sand for dustbathing, pecking and scratching in domestic chicks. Applied Animal Behaviour Science, 43,

16 14 DIXON AND DUNCAN Savory, C. J., & Mann, J. S. (1999). Feather pecking in groups of growing bantams in relation to floor litter substrate and plumage colour. British Poultry Science, 40, Van de Weerd, H. A., Docking, C. M., Day, J. E. L., & Edwards, S. A. (2005). The development of harmful social behaviour in pigs with intact tails and different enrichment backgrounds in two housing systems. Animal Science, 80, Vestergaard, K. S. (1982a). Dust-bathing in the domestic fowl: Diurnal rhythm and dust deprivation. Applied Animal Ethology, 8, Vestergaard, K. S. (1982b). The significance of dustbathing for the well being of the domestic hen. Tierhaltung, 113, Vestergaard, K. S. (1994). Dustbathing and its relation to feather pecking in the foul: Motivational and developmental aspects. Unpublished doctoral dissertation, Royal Veterinary and Agricultural University, Copenhagen, Denmark. Vestergaard, K. S., Kruijt, J. P., & Hogan, J. A. (1993). Feather pecking and chronic fear in groups of red junglefowl: Their relations to dustbathing, rearing environment and social status. Animal Behaviour, 45,