Gentle Feather Pecking Research Articles

Comparison of the welfare of layer hens in 4 housing systems in the UK

1. The welfare of hens in 26 flocks (6 conventional cage, 6 furnished cage, 7 barn, 7 free-range) was assessed throughout the laying period using a combination of data on physical health, physiology and injurious pecking, collected by researchers on farm and during post-mortem analysis, and information submitted by producers. 2. There was an effect of housing system on 5 of the indicators recorded by researchers: gentle feather pecks given, feather damage score, proportion of hens with feather damage, proportion of the flock using perches, and faecal corticosterone. 3. Post-mortem analysis revealed several differences between housing systems in skin damage, plumage damage to the vent and abdomen, keel protrusion, bodyweight, and the proportion of hens that were vent pecked and that had old and recent keel fractures. 4. There was an effect of housing system on 5 indicators recorded by producers: proportion of egg shells with calcification spots, proportion of egg shells with blood stains, weight of hens found dead, temporal change in the proportion of egg shells with stains, and temporal change in proportion of hens found dead. 5. Each housing system had positive and negative aspects but overall, hens in barn systems had the highest prevalence of poor plumage condition, old fractures, emaciation, abnormal egg calcification, and the highest corticosterone. Hens in conventional cages sustained more fractures at depopulation than birds in other systems. Vent pecking was most prevalent in free-range flocks. The lowest prevalence of problems occurred in hens in furnished cages. 6. Although housing system had an influence on the hens’ physical condition and physiological state, the high prevalence of emaciation, loss of plumage, fractures and evidence of stress is of concern across all housing systems, and suggests that the welfare of modern genotypes is poor.

The risk factors affecting the development of gentle and severe feather pecking in loose housed laying hens

Injurious pecking remains one of the biggest problems challenging free range egg producers, with both economic implications for the farmer and welfare implications for the birds. The most widespread form of injurious pecking is feather pecking, the most damaging form of which is severe feather pecking (SFP) which has, as yet unclear, links with gentle feather pecking (GFP). The current prospective epidemiological study investigates the development of GFP and SFP on 61 free range and organic UK farms (111 flocks). Flocks were visited at 25 (20–30) and 40 (35–45) weeks, when rates of GFP and SFP respectively and levels of feather damage were recorded. Environmental and management data were collected for each flock. Factors affecting the development of these behaviours were modelled using the multilevel modelling program, MLwiN ( Rasbash et al., 2004). GFP was observed in 89.2% and 73% of flocks at 25 and 40 weeks, respectively, at a mean rate of 0.65 bouts/bird/h. GFP rates decreased with increased percentage range use (coeff.: −0.001 ± 0.0006, p = 0.025) and temperature inside the laying house (coeff.: −0.005 ± 0.001, p = 0.001). GFP was higher in flocks with soil or grass litter ( χ 2 = 13.16, df = 4, p = 0.012), flocks which had no perch access (0.010 ± 0.001 vs. 0.007 ± 0.002 bouts/bird/min, p = 0.047) and flocks which were beak trimmed compared to those non-beak trimmed or retrospectively beak trimmed (0.013 ± 0.002 vs. 0.003 ± 0.001 and 0.002 ± 0.001, p = 0.007). SFP was observed in 68.5% and 85.6% of flocks at the 1st and 2nd visits, respectively, at a mean rate of 1.22 bouts/bird/h. SFP rates decreased with range use (coeff.: −0.001 ± 0.0003, p = 0.003). Mean rates were highest in non-beak trimmed compared to beak trimmed flocks (0.032 ± 0.003 vs. 0.017 ± 0.003 bouts/bird/min, p = 0.028), flocks observed to be feather pecking when they arrived on farm compared to those that were not (0.062 ± 0.018 vs. 0.019 ± 0.002 bouts/bird/min, p = 0.001), and flocks fed pelleted compared to those fed mashed food (0.042 ± 0.002 vs. 0.016 ± 0.002 bouts/bird/min, p = 0.005). Plumage damage was lower in beak trimmed compared to non-beak trimmed flocks (plumage score 1.00 ± 0.0001 vs. 1.15 ± 0.068, p = 0.040), and flocks which were fed mashed feed, and showed a quadratic relationship with severe feather pecking ( p = 0.003) which was positive over the observed ranges of the behaviours. In commercial situations, feeding mashed feed and increasing range use may reduce severe feather pecking and therefore feather damage.

Taste aversion learning to eliminate feather pecking in laying hens, Gallus gallus domesticus

Feather pecking in laying hens is a redirection of normal pecking behaviour. There is clear evidence that severe feather pecking is influenced by the motivational system of foraging and feeding. Feather pecking is positively associated with feather eating, indicating that feathers are seen as a feeding substrate by laying hens. Feed choice may be affected by many factors, including learning processes. In this experiment, feathers of other birds were made distasteful by adding a bitter taste (quinine). We investigated whether laying hens could detect quinine and learn to avoid the feather cover of conspecifics. We also examined the effects of quinine on birds' own feather-related activity (preening). Six groups of 10 high feather-pecking birds and six groups of 10 low feather-pecking birds were kept on litter. Half of these groups were quinine treated. Each bird of the quinine-treated groups was individually sprayed with a quinine solution. We investigated whether the presence of quinine on birds' feather cover affected severe and gentle feather pecking, aggressive pecking and preening. In the present study, severe and gentle feather pecking decreased when feathers were made distasteful, suggesting that learning occurred. Furthermore, the results suggest that quinine is an effective reinforcing agent to alter feather-pecking behaviour. Distasteful feathers did not influence preening, whereas aggressive behaviour was reduced. Our experiment showed that birds in the quinine treatment were able to learn that feathers from conspecifics were not attractive to peck at and they learned to avoid them for a period of time.

Form but not frequency of beak use by hens is changed by housing system

In order to verify the hypothesis that hens in different housing systems have the same time budget for different beak-related behaviours, we compared the pecking behaviour of hens in six housing systems: small (SC) and large (LC) conventional cages, small (SF) and large (LF) furnished cages, single-tiered aviary (SA), and free-range (FR). At the age of 16 weeks, 284 medium hybrid layers were randomly divided into six groups and moved to the six housing systems. The number of hens performing behaviours using the beak (grazing, eating, drinking, preening, aggressive pecking, gentle feather pecking, severe feather pecking, litter pecking, and object pecking) was recorded at various ages up to 63 weeks of age. Grazing by a large proportion of hens was observed in FR, and litter pecking by a large proportion of hens in SA. The proportions of hens eating, drinking, and preening were higher in SC, LC, SF, and LF than in SA, and higher in SA than in FR (all P < 0.05). The proportion of hens performing object pecking was higher in SC and LC than in the other systems (all P < 0.05). The proportion of hens performing severe feather pecking was higher in LF and SA than in FR, and more in FR than in SC, LC, and SF (all P < 0.05). The percentages of hens performing all pecking behaviours were almost identical among the six housing systems (63.0 ± 7.1% in SC, 63.0 ± 5.9% in LC, 65.6 ± 5.4% in SF, 64.7 ± 5.0% in LF, 62.9 ± 5.9% in SA, and 64.9 ± 5.6% in FR), indicating that the total frequency of beak use was almost the same regardless of the housing system, although the breakdown of types of beak use was different. We conclude that caged hens may express a motivation for beak-related behaviour by directing it at food, drinking nipples, their own feathers, and the cage wires, although feather pecking appeared not to be decreased simply by the redirected pecking.

Behaviour when young as a predictor of severe feather pecking in adult laying hens: The redirected foraging hypothesis revisited

It has been suggested that feather pecking in poultry results when foraging behaviour is redirected to feathers in the absence of adequate foraging incentives and that gentle feather pecking is a precursor of severe feather pecking. Associations have also been proposed between feather pecking and other behaviours including dust bathing and preening. Here, we present the results of a longitudinal study on the development of severe feather pecking in individual domestic fowl. We hypothesised that behaviour, and especially foraging and gentle feather pecking behaviour, of individual birds when young predicts severe feather pecking behaviour by the same birds when adult. To test this hypothesis, we used behavioural data collected from 192 individual White Leghorn hens (12 focal birds/group) housed continuously from hatch in 16 floor pens. Data on 34 behaviour variables recorded when the birds were young (3–15 weeks of age) were subjected to factor analysis. The resulting factors were entered as independent variables in a generalised linear model to determine their relationship with severe feather pecking by the same birds as adults (17–37 weeks of age). We found a positive association between a factor describing foraging when young and severe feather pecking when adult, and a negative association between a factor describing dust bathing when young and severe feather pecking when adult ( P < 0.05). Levels of severe feather pecking increased following the onset of lay and we found no significant association between factors describing feather pecking when young and severe feather pecking by the same individuals when adult. Most of the birds were observed to perform exploratory gentle feather pecks when young. No evidence was found that exploratory or stereotyped gentle feather pecks consistently became more severe over time but factor analysis indicated that severe feather pecking by young birds was more closely correlated with exploratory, than stereotyped, gentle feather pecking, signalling utility in distinguishing between exploratory and stereotyped gentle feather pecking in future studies. We conclude that severe feather pecking did not substitute for foraging behaviour but, rather, was more likely to emerge in adult hens that had performed relatively more foraging, and less resting and dust bathing, when young. However, none of the individual behaviour variables recorded when young could be used to identify precisely which individuals would exhibit severe feather pecking when adult.

Effect of brooders on feather pecking and cannibalism in domestic fowl ( Gallus gallus domesticus)

Several studies have shown that the tendency to feather peck is influenced by events early in life and preventive measures should therefore be introduced at hatching. Separating inactive chicks from active chicks by providing dark electrical brooders was predicted to reduce the risk of chicks developing pecking preferences for conspecifics. Twelve groups of 15 layer hen chicks (Lohmann Tradition) were reared in pens (2.55 m 2); during the first 5 weeks after hatching six pens were provided with dark brooders and six pens with heating lamps. All pens were observed continuously for 30 min per pen once a week until the chickens were 23 weeks old, and each bout of severe feather pecks was recorded. The chickens were observed several times daily, and all injured individuals were removed from the experiment. Faecal samples were collected from the pens when the chicks were 16, 17 and 18 days old and analysed for corticosterone metabolites. At the end of the experiment, the plumage and skin damage were scored. Data were analysed using repeated measures ANOVA. The dark brooders completely prevented severe feather pecking in the dark brooder pens, whereas the frequency of severe feather pecking rose with age in the heating lamp pens (treatment × age: P < 0.0001). At the last observation (week 23), the frequency of severe feather pecking bouts in the dark brooder pens was 0.3 ± 0.4 (mean ± S.E.) compared to 31.3 ± 10.1 in the heating lamp pens. The frequency of gentle feather pecking was significantly higher in the heating lamp pens at all ages ( P < 0.0001). Mortality followed the same pattern as severe feather pecking; it was almost non-existent in the dark brooder pens, whereas from point of lay it continued to rise with age in the heating lamp pens (1 versus 24 casualties, treatment × age: P < 0.0001). The high level of severe feather pecking in the heating lamp pens was also reflected in the scores of plumage and skin damage as both were found to be significantly higher in the heating lamp pens (plumage: P = 0.0004; skin: P = 0.0273). There was no difference between treatments in concentrations of faecal corticosterone metabolites ( P = 0.8146). The results suggest that the provision of dark brooders has a long-lasting reducing effect on the frequency of feather pecking and cannibalistic attacks, resulting in reduced mortality and an improved condition of both plumage and skin.

Assessing the welfare consequences of providing litter for feed-restricted broiler breeders

1. Broiler breeder females were fed restricted allocations of a standard wheat–soy ration to meet target body weights. They were housed on raised plastic slotted floors (S) or wood shavings litter (L) from hatch to 8 weeks when each pen of 12 birds was transferred to another pen in the same block in a 2 × 2 factorial experiment (LL, LS, SL and SS). Measures of bird welfare were taken at 4 weeks of age, and at 9 and 10 weeks following transfer to the new pens. 2. At 4 weeks of age, birds reared on S spent more time standing, pecking the feeder, the wall and other birds and less time pecking the floor compared with those on L. Gentle feather pecks, strong feather pecks and strong feather pulls were more common in S than L. 3. Mean body weight was higher and coefficient of variation lower in birds on L than S at the end of the experiment. Feather loss and damage scores at 10 weeks were higher for birds reared from hatch to 8 weeks on S. 4. Birds that were reared on S continued to peck more at the pen walls after transfer to new pens but there was no other carry-over effect on behaviour. Birds on S at 9 and 10 weeks pecked more at the walls and less often at the floor, and rested less often. There was more feather pecking on S than on L in the second week post transfer. 5. Tonic immobility was greater and plasma corticosterone concentrations were lower at the end of the experiment in birds on L than S at 9 and 10 weeks of age. The heterophil–lymphocyte ratio was similar between treatments at 4 weeks and after the birds were moved to a new pen. 6. The results are consistent with the view that litter and wall pecking has de-arousing properties and that this activity is re-directed foraging that diminishes the stress of feed restriction.

Comparisons of damaging feather pecking and time budgets in male and female turkeys of a traditional breed and a genetically selected male line

Feather and skin pecking leading to feather loss and tissue damage is a welfare problem in commercial turkeys. A factorial experiment was designed to compare a line of unselected turkeys that previously did not exhibit this behaviour with a genetically selected male line with a propensity for damaging pecking. We also compared the time budgets of male and female turkeys from the two lines at 3, 6 and 9 weeks of age and at different times of the day. Damaging feather pecking occurred in 32% of male and 15% of female male line turkeys but was not observed in the traditional line. Time budgets of males and females were similar. Preening increased and resting, feeding and general pecking declined with age. Resting was higher in the afternoon than in the morning and male line turkeys were observed resting more often than traditional turkeys at 3 and 6 weeks. Traditional turkeys displayed more gentle feather pecks than male line poults at 9 weeks. Male turkeys of both lines showed more strong feather pecks and pulls at 3 weeks whereas female turkeys showed more at 9 weeks of age. The frequency of strong feather pulls recorded electronically increased with age but was not related to mortality. It is suggested that damaging feather pecking in turkeys may be the result of vigorous investigative pecking.

The development of feather pecking in Burmese red junglefowl: the influence of early experience with exploratory-rich environments

This study examines the development of feather pecking and its relationship to exploration in Burmese red junglefowl ( Gallus gallus spadiceus). Ten groups of four chicks each were raised from hatching on wire mesh floors (home pen). Two of the four chicks in each group received experience in exploratory-rich environments four times a week for 5 weeks, and the other two chicks remained in the home pen. Observations conducted in the home pen revealed that chicks deprived of experience in exploratory-rich environments performed significantly more gentle feather pecking, and tended to show more severe feather pecking than the experienced birds. Experience in the exploratory-rich environments did not affect the frequency of environmental pecking or food pecking. These results suggest that chicks deprived of exploratory-rich environments may come to perceive pen mates as appropriate exploratory stimuli and subsequently direct exploratory behavior toward conspecifics. This tendency to peck pen mates may lead to the development of feather pecking. We suggest that forceful pecks may be reinforcing, and that the more likely pecks are directed to a conspecific, the more likely feather pecking will develop.

Can short-term frustration facilitate feather pecking in laying hens?

Feather pecking is a major problem in laying hens. Frustration, i.e. the omission of expected reward, may play a role in the development of feather pecking. In two experiments, we studied if feather pecking could be facilitated by short-term frustration in birds with a high feather pecking phenotype and victims of feather pecking (experiment 1), and in birds with a high or low feather pecking genotype (experiment 2). Furthermore, the motivation to peck a key for a food reward was assessed in birds with a high or low feather pecking genotype in experiment 3, as birds that have a stronger motivation may also react stronger to the omission of a reward. We trained birds to peck a key for a food reward in an automated Skinnerbox and tested them in control and frustration sessions. During frustration, the feeder was covered with Perspex. Frustration did not facilitate feather pecking in either experiment. In experiment 1, birds with a high feather pecking phenotype did show more gentle feather pecking and aggressive pecking than victims of feather pecking during some of the control sessions. Furthermore, victims of feather pecking vocalised more than birds with a high feather pecking phenotype. In experiment 2, birds with a high feather pecking genotype scratched more than birds with a low feather pecking genotype, indicating differences in motivation for foraging or dust-bathing behaviour, which shows a relation to feather pecking. Birds with a low feather pecking genotype also had a stronger motivation to peck at a key for a food reward than birds with a high feather pecking genotype. No evidence was found that feather pecking could be facilitated by short-term frustration in a Skinnerbox. However, differences in reaction to frustration and in motivation to peck a key for a food reward in birds with a high or low feather pecking phenotype or genotype indicate that frustration may still play a role in the development of feather pecking.

Chronic increase of dietary l-tryptophan decreases gentle feather pecking behaviour

Many studies show the involvement of the serotonergic (5-HT) system in the performance of abnormal behaviour in both human and animals. Recently, we showed that acute reduction of 5-HT turnover in the forebrain, increased gentle and severe feather pecking behaviour in chicks from a high (HFP) and low feather pecking (LFP) line of laying hens, suggesting that the performance of feather pecking behaviour involves low 5-HT neurotransmission. In the present study, we postulated that if low 5-HT is causally underlying feather pecking, increasing 5-HT turnover in the forebrain will decrease the development and performance of feather pecking. Augmentation of 5-HT neurotransmission in the brain was induced by chronically increasing dietary levels of the essential amino acid l-tryptophan (TRP) from which 5-HT is synthesised. From the age of 34 days, LFP and HFP chicks were fed a diet containing 2% TRP, whereas control birds of both lines were continuously fed with the normal rearing feed (0.16% TRP). From 35 days of age, litter was removed from the pens (10 pens/line-treatment) and all chicks (10 chicks/pen) were housed on a slatted floor until the end of the experiment. At 49 days of age, feather pecking behaviour was studied for 30 min. At 50 days of age baseline corticosterone, TRP and other large amino acids (LNAAs) were measured in the blood plasma of decapitated chicks (10 chicks per line-treatment). Furthermore, plasma corticosterone and central 5-HT turnover levels in response to manual restraint (5 min) were determined (10 chicks/line-treatment). For neither gentle nor severe feather pecking a significant line × treatment interaction was found. However, TRP treatment resulted in a significant [ P = 0.02] overall decrease of the frequency of gentle feather pecking. For severe feather pecking a similar but not significant pattern was found. Significant line effects were found for gentle and severe feather pecking. HFP birds showed significantly higher levels of gentle and severe feather pecking behaviour than LFP birds [ P < 0.001]. TRP treatment significantly increased the TRP/LNAA ratio in the plasma of the chicks. Furthermore, TRP treatment overall increased baseline and stress-induced levels of plasma corticosterone (although more pronounced in the LFP line). TRP supplementation significantly increased 5-HT turnover in the hippocampus and archistriatum and tended to do so in the remainder of the forebrain. The results confirm our hypothesis that feather pecking behaviour is triggered by low serotonergic neurotransmission, as increasing serotonergic tone, by increasing dietary TRP, decreases gentle feather pecking behaviour.

Genetic and phenotypic correlations between feather pecking and open-field response in laying hens at two different ages.

The object of this research was to study the relationship between feather pecking and open-field activity in laying hens at two different ages. A population of 550 birds of a laying hen cross was subjected to an open-field test at 5 and 29 weeks of age and to a social feather pecking test at 6 and 30 weeks of age. Factor analysis was used to identify underlying factors for each test: pecking behavior (social test) and open-field activity (open-field test). In young birds, a positive phenotypic correlation of 0.24 was found between high open-field activity and high levels of pecking behavior (ground pecking, preening, gentle feather pecking, and wall pecking). In adults, a similar genetic correlation of 0.62 was found. At adult age, the factor pecking behavior consisted mainly of gentle and severe feather pecking. Between ages, a strong, negative genetic correlation of -0.65 was found between open-field activity at young age and pecking behavior at adult age, indicating that open-field activity levels in young birds may predict pecking behavior in adult hens.

Genetic and Phenotypic Correlations Between Feather Pecking Behavior, Stress Response, Immune Response, and Egg Quality Traits in Laying Hens

The objective of the current study was to estimate genetic and phenotypic correlations among feather pecking (FP) behavior and stress response, immune response, and egg quality parameters. These traits have been measured in an F2 cross, coming from a cross between a high and a low FP line of laying hens. Heritabilities (h2) of stress response (32 wk), primary immune response to keyhole limpet hemocyanin (KLH) (36 wk) and Mycobacterium butyricum (39 wk), and egg quality parameters (35, 44, and 50 wk of age) were calculated. The h2 was 0.05 ± 0.05 (SE) for stress response, 0.15 ± 0.07 for antibody response to KLH, and 0.08 ± 0.06 for antibody response to M. butyricum. The h2 for egg quality traits were in the range of 0.12 to 0.30. Significant phenotypic correlations were found between gentle FP in adult hens and stress response, egg weight at 44 and 50 wk, and egg deformation at 50 wk. Significant additive genetic correlations were found between severe FP in adult hens and antibody response to KLH (0.79 ± 0.35), and between ground pecking in adult hens and egg deformation at 50 wk (0.63 ± 0.26), and between ground pecking and eggshell strength at 35, 44, and 50 wk of age (-0.86 ± 0.29, -0.81 ± 0.20, -0.76 ± 0.24, respectively).

Prenatal light exposure affects early feather-pecking behaviour in the domestic chick

Recently we proposed that early feather pecking is a form of social exploration. Social recognition, important for exploration, is a lateralized function in the domestic chick. Lateralization of functions can be influenced by light exposure late in embryonic development. Therefore, we investigated whether this light exposure affected early posthatching feather-pecking behaviour in domestic chicks, Gallus gallus domesticus. White leghorn embryos either were exposed to light or remained in darkness in the last week of incubation. After hatching, they were housed in groups of two light-exposed and two dark-incubated chicks. Light-exposed chicks showed more feather pecking than did their dark-incubated cagemates. Dark-incubated chicks preferred to direct feather pecks to unfamiliar peers than to familiar peers; light-exposed chicks showed no preference. These effects were present in the first week after hatching and remained at least another 3 weeks. These results support the hypothesis that early gentle feather pecking is part of the normal behavioural repertoire of young chicks and influences social exploration. We discuss a possible mechanism underlying these results. We also suggest that it may be worthwhile not to expose embryos to light during the last week of incubation when housing hatchlings in commercial conditions, where feather pecking is a serious problem.

Feather pecking in laying hens: new insights and directions for research?

The aim of this paper is to present new insights and promising directions for future research on feather pecking in laying hens. Our starting point was a multidisciplinary research program on feather pecking in The Netherlands, in which ethological, physiological, ontogenetic and genetic approaches were combined. The four topics addressed in this paper are: (1) the relation between gentle and severe feather pecking, (2) feather pecking and coping strategy, (3) causation of feather pecking, and (4) the possibility to solve the problem of feather pecking through genetic selection. When the relationship between gentle and severe feather pecking was studied, it was found that both forms of feather pecking are related at the same age. Gentle feather pecking at young age, however, could not be used as a predictor of feather pecking at adult age. Birds from high and low feather pecking lines that showed differences in feather pecking also differed in other behavioural and physiological characteristics. This may reflect line differences in coping strategy. Relating coping strategy with feather pecking may help us to better understand the motivations and characteristics underlying the development of feather pecking. On the causation of feather pecking, there is some evidence that it is redirected ground pecking, deriving either from a foraging or a dustbathing background. However, evidence was found that early feather pecking could also be interpreted as social exploration. Finally, the use of molecular genetics to help solving the problem of feather pecking seems promising. Feather pecking has been shown to be heritable and the first genetic regions (QTL) involved in feather pecking have been identified. To search for a solution for the feather pecking problem it is of importance to identify the mechanisms involved in the development of feather pecking. In this paper, we have combined approaches from different disciplines in order to study feather pecking. The results indicate that combined efforts of multidisciplinary research can be very useful in looking for possible ways to reduce feather pecking in practice.

Identification of quantitative trait loci for receiving pecks in young and adult laying hens

Feather pecking (FP) is a major problem in cage and free-range housing systems. In free-range systems, FP is more difficult to control. It is not known why a victim is being pecked. It could be that a bird is genetically predisposed to be pecked. To study the genetics of FP behavior, a large F2 population of 630 hens was generated from a cross between two commercial laying lines differing in their propensity to feather peck. The traits measured at 6 and 30 wk of age were receiving gentle FP, receiving severe FP, and receiving aggressive pecking. In addition, receiving toe pecking (TP) was also measured at 30 wk of age. For receiving gentle FP at 6 wk of age, a significant QTL on GGA1 and three different suggestive QTL were identified on GGA2, GGA6, and GGA7, respectively. For receiving gentle FP at 30 wk of age, a suggestive QTL on GGA5 was detected. For receiving aggressive pecking, a suggestive QTL was detected on GGA3. For receiving TP, three suggestive QTL were detected on GGA1, GGA5, and GGA23, respectively. The different QTL detected for receiving gentle FP at different ages indicate that this trait is regulated by different genes in young and adult hens.

Mapping quantitative trait loci affecting feather pecking behavior and stress response in laying hens

In the European Union, legislation concerning animal housing is becoming stricter because of animal welfare concerns. Feather pecking (FP) in large group housing systems is a major problem. It has been suggested that corticosterone (CORT) response to manual restraint as a measure for stress is associated with FP behavior. The aim of the current study was to identify QTL involved in FP behavior and stress response in laying hens. An F2 population of 630 hens was established from a cross between two commercial lines of laying hens differing in their propensity to feather peck. The behavioral traits, measured at 6 and 30 wk of age, were gentle FP, severe FP, and aggressive pecking. Toe pecking was measured at 30 wk of age and CORT response to manual restraint was measured at 32 wk. All animals were genotyped for 180 microsatellite markers. A QTL analysis was performed using a regression interval mapping method. At 6 wk of age, a suggestive QTL on GGA10 was detected for gentle FP. At 30 wk of age, suggestive QTL were detected on GGA1 and GGA2 for gentle FP. A significant QTL was detected on GGA2 for severe FP. At 32 wk of age, a suggestive QTL was detected on GGA18 for CORT response to manual restraint. In addition, a suggestive QTL was detected on GGA5 with possible maternal parent-of-origin effect for CORT response.

Heritability of feather pecking and open-field response of laying hens at two different ages

The objective of the current study was to estimate heritabilities (h2) of feather pecking and open-field response of laying hens at two different ages. An F2 cross, originating from a high and a low feather pecking line of laying hens, was used for the experiment. Each of the 630 birds of the F2 cross was subjected to an open-field test (individual, 10 min) at 5 and 29 wk of age and to a social feather pecking test (groups of five birds on wood shavings, 30 min) at 6 and 30 wk of age. Both tests were performed in a square open field (1.25 × 1.25 m). Behavior was recorded directly from a monitor. Heritabilities of feather pecking and open-field behaviors were calculated. In the open-field test at 5 wk of age, high h2 were found for most traits, ranging from 0.20 for the frequency of flying to 0.49 for number of steps. In the social test at 6 wk, gentle feather pecking (0.12) and ground pecking (0.13) were found to be heritable. When both tests were repeated at 29 and 30 wk of age, h2 estimates were lower for the open-field test, ranging from 0.10 for duration of sitting to 0.20 for latency to first step. In the social test, however, higher h2 estimates of 0.15 for gentle feather pecking and 0.30 for ground pecking were found compared with 6 wk of age. In conclusion, gentle feather pecking and open-field behaviors may be used in selection against feather pecking.

Comparison of individual and social feather pecking tests in two lines of laying hens at ten different ages

The aim of this experiment was to select a suitable test to measure feather pecking in laying hens. Pecking behaviour in individual and social feather pecking tests was compared with pecking behaviour in the homepen. Two lines of laying hens were used that differ in their propensity to display feather pecking: the high feather pecking (HFP) and low feather pecking (LFP) lines. Six groups of five birds per line were housed on wood shavings with ad libitum food and water. From 7 to 34 weeks of age, every 3 weeks pecking behaviour in the homepen was observed and three feather pecking tests were conducted as well: one individual test with a bunch of feathers (10 min) and two social tests (in random order), one with and one without a bunch of feathers (30 min with whole group). Observations focused on gentle and severe feather pecking, bunch pecking, ground pecking and preening. In the individual test, general activity and vocalisations were recorded as well, to measure the response to isolation. In general, HFP birds showed more gentle and severe feather pecking than LFP birds, whereas LFP birds showed more ground pecking and, unexpectedly, more bunch pecking. Birds that showed gentle feather pecking in the homepen also showed gentle feather pecking and bunch pecking in the social tests over all ages. Severe feather pecking in the social test with a bunch of feathers corresponded with severe feather pecking in the homepen. Bunch pecking in the individual test was not a reliable measure for feather pecking in this experiment. An increasing number of vocalisations in the HFP line and a decreasing number in the LFP line indicated a difference in reaction to the individual test. In conclusion, gentle and severe feather pecking and bunch pecking in the social test corresponded best with homepen behaviour, whereas bunch pecking in the individual test did not.

The development of feather pecking behaviour and targeting of pecking in chicks from a high and low feather pecking line of laying hens

Large individual differences between adult laying hens in their propensity for feather pecking are known to exist. However, not much research has been carried out into the individual differences concerning the development of feather pecking behaviour. The purpose of this study was to investigate whether contrasting levels of feather pecking, observed among adult birds from two lines of laying hens, already occur at an early age. Furthermore, an important question to be discussed was whether different behavioural systems may be related to the occurrence of feather pecking. Therefore, this study consisted of studying and comparing the behaviour of White Leghorn laying hens from a high (HFP) and low feather pecking line (LFP) during the first 8 weeks of life. Chicks were reared in litter-floor pens and were kept in groups of five animals per line (12 groups per line).HFP chicks showed significantly higher levels of gentle feather pecking (gentle FP) than LFP chicks at the age of 14 and 28 days. Furthermore, HFP chicks spent significantly more time preening than LFP chicks on days 14, 28 and 41. Duration of foraging behaviour and feeding behaviour was significantly higher in the LFP line compared to the HFP line on days 41 and 56 and days 28, 41 and 56, respectively. HFP chicks showed a significant negative correlation between gentle FP and preening on days 3 (r=−0.49) and 41 (r=−0.86). In the LFP line duration of feeding correlated negatively with gentle FP on day 3 (r=−0.63). A principal component analysis (PCA) revealed that in the HFP line, gentle FP and preening exhibited high and opposite loadings on the same component at all ages, whereas feeding consistently loaded on the other component. This outcome contrasted with that of the LFP line. In this line feeding predominantly loaded on the same principal component as gentle FP, with loadings opposite to those of gentle FP, whereas preening showed the same loadings as gentle FP, on days 3 and 41.In conclusion, differences in feather pecking behaviour between HFP and LFP chicks can already be observed at a very early age during development. Furthermore, our results indicate that HFP and LFP chicks differ in the way pecking behaviour is targeted. This difference could be related to the existence of a difference in underlying motivational system controlling the development of feather pecking between the two lines.