Stress response, peripheral serotonin and natural antibodies in feather pecking genotypes and phenotypes and their relation with coping style

Feather pecking (FP), a serious welfare and economic issue in the egg production industry, has been related to coping style. Proactive and reactive coping styles differ in, among others, the stress response, serotonergic activity and immune activity. Yet, it is unknown whether genetic lines divergently selected on FP (i.e. FP genotypes) or individuals differing in FP (i.e. FP phenotypes) can be categorized into coping styles. Therefore, we determined peripheral serotonin (5-HT) levels, natural antibody (NAb) titers, behavioral and corticosterone (CORT) responses to manual restraint (MR) in FP genotypes (high FP (HFP), low FP (LFP) and unselected control (CON) line) and FP phenotypes (feather pecker, feather pecker-victim, victim and neutral). We further examined the consistency of and relationships between behavioral and physiological measures. FP genotypes differed in behavioral responses to MR, 5-HT levels and NAb titers, but not in CORT levels after MR. HFP birds had less active responses at adolescent age, but more active responses at adult age compared to LFP and CON birds. The CON line had higher 5-HT levels at adolescent age, while the HFP line had lower 5-HT levels than the other lines at adult age. Overall, the HFP line had lower IgM NAb titers, while the LFP line had lower IgG NAb titers compared to the other lines. FP phenotypes differed in behavioral responses to MR and 5-HT levels, but not in CORT levels after MR or NAb titers. Within the HFP line, feather peckers tended to have less active responses compared to neutrals at adolescent age, while victims had more active responses compared to the other phenotypes at adult age. Feather peckers had higher 5-HT levels than neutrals at adult age. Behavioral and CORT responses to MR were not consistent over time, suggesting that responses to MR might not reflect coping style in this study. Furthermore, proactive behavioral responses were correlated with reactive physiological measures and vice versa. Thus, it was not possible to categorize FP genotypes or FP phenotypes into specific coping styles.</p

Feather pecking genotype and phenotype affect behavioural responses of laying hens

Feather pecking (FP) is a major welfare and economic issue in the egg production industry. Behavioural characteristics, such as fearfulness, have been related to FP. However, it is unknown how divergent selection on FP affects fearfulness in comparison to no selection on FP. Therefore, we compared responses of birds selected on low (LFP) and high feather pecking (HFP) with birds from an unselected control line (CON) to several behavioural tests (i.e. novel object (NO), novel environment (NE), open field (OF) and tonic immobility (TI)) at young and adult ages. Furthermore, the relation between actual FP behaviour (i.e. FP phenotypes) and fearfulness is not well understood. Therefore, we compared responses of birds with differing FP phenotypes. Feather pecking phenotypes of individual birds were identified via FP observations at several ages. The number of severe feather pecks given and received was used to categorize birds as feather peckers, feather pecker-victims, victims or neutrals. Here we show that HFP birds repeatedly had more active responses (i.e. they approached a NO sooner, vocalized sooner and more, showed more flight attempts and had shorter TI durations), which could indicate lower fearfulness, compared to CON and LFP birds at both young and adult ages. Within the HFP line, feather peckers had more active responses (i.e. they tended to show more flight attempts compared to victims and tended to walk more compared to neutrals), suggesting lower fearfulness, compared to victims and neutrals. Thus, in this study high FP seems to be related to low fearfulness, which is opposite to what previously has been found in other experimental and commercial lines. This stresses the need for further research into the genetic and phenotypic correlations between FP and fearfulness in various populations of chickens, especially in commercial lines. Findings from experimental lines should be used with caution when developing control and/or prevention methods that are to be applied in commercial settings. Furthermore, activity and/or coping style might overrule fearfulness within the HFP line, as HFP birds and feather peckers within the HFP line had more active responses. This might indicate a complex interplay between fearfulness, activity and coping style that could play a role in the development of FP.</p

Individuality of a group: detailed walking ability analysis of broiler flocks using optical flow approach

Impaired walking ability is one of the most important factors affecting broiler welfare. Routine monitoring of walking ability provides insights in the welfare status of a flock and assists farmers in taking remedial measures at an early stage. Several computer vision techniques have been developed for automated assessment of walking ability, providing an objective and biosecure alternative to the currently more subjective and time-consuming manual assessment of walking ability. However, these techniques mainly focus on assessment of averages at flock level using pixel movement. Therefore, the aim of this study was to investigate the potential of optical flow algorithms to identify flock activity, distribution and walking ability in a commercial setting on levels close to individual monitoring. We used a combination of chicken segmentation and optical flow methods, where chicken contours were first detected and were then used to identify activity, spatial distribution, and gait score distribution (i.e. walking ability) of the flock via optical flow. This is a step towards focusing more on individual chickens in an image and its pixel representation. In addition, we predicted the gait score distribution of the flock, which is a more detailed assessment of broiler walking ability compared to average gait score of the flock, as slight changes in walking ability are more likely to be detected when using the distribution compared to the average score. We found a strong correlation between predicted and observed gait scores (R2 = 0.97), with separate gait scores all having R2 > 0.85. Thus, the algorithm used in this study is a first step to measure broiler walking ability automatically in a commercial setting on a levels close to individual monitoring. These validation results of the developed automatic monitoring of flock activity, distribution and gait score are promising, but further validation is required (e.g. for chickens at a younger age, with very low and very high gait scores)

Where in the serotonergic system does it go wrong? Unravelling the route by which the serotonergic system affects feather pecking in chickens

A deficient serotonergic system is associated with psychopathological behaviors in various species, among which, feather pecking (FP) in chickens. Deficiency in the serotonergic system can predispose birds to develop FP, while the serotonergic system is affected in birds that feather peck. Serotonin (5-HT) can further influence dopamine (DA) activity. Lines with high FP tendency generally have low central 5-HT and DA turnovers at a young age, but high turnovers at an adult age in brain areas involved in somato-motor regulation and goal-directed behavior. Agonizing 5-HT1A and 5-HT1B receptors increases FP, while antagonizing D2 receptor reduces FP. Genetic associations exist between FP, 5-HT1A and 5-HT1B receptor functioning and metabolism of 5-HT and DA. Birds with deficient functioning of the somatodendritic 5-HT1A autoreceptor and 5-HT metabolism appear predisposed to develop FP. Birds which feather peck often eat feathers, have low whole-blood 5-HT, different gut-microbiota composition and immune competence compared to non-peckers. FP and feather eating likely affect the interaction between gut microbiota, immune system and serotonergic system, but this needs further investigation.</p

Stress response, peripheral serotonin and natural antibodies in feather pecking genotypes and phenotypes and their relation with coping style

Feather pecking (FP), a serious welfare and economic issue in the egg production industry, has been related to coping style. Proactive and reactive coping styles differ in, among others, the stress response, serotonergic activity and immune activity. Yet, it is unknown whether genetic lines divergently selected on FP (i.e. FP genotypes) or individuals differing in FP (i.e. FP phenotypes) can be categorized into coping styles. Therefore, we determined peripheral serotonin (5-HT) levels, natural antibody (NAb) titers, behavioral and corticosterone (CORT) responses to manual restraint (MR) in FP genotypes (high FP (HFP), low FP (LFP) and unselected control (CON) line) and FP phenotypes (feather pecker, feather pecker-victim, victim and neutral). We further examined the consistency of and relationships between behavioral and physiological measures. FP genotypes differed in behavioral responses to MR, 5-HT levels and NAb titers, but not in CORT levels after MR. HFP birds had less active responses at adolescent age, but more active responses at adult age compared to LFP and CON birds. The CON line had higher 5-HT levels at adolescent age, while the HFP line had lower 5-HT levels than the other lines at adult age. Overall, the HFP line had lower IgM NAb titers, while the LFP line had lower IgG NAb titers compared to the other lines. FP phenotypes differed in behavioral responses to MR and 5-HT levels, but not in CORT levels after MR or NAb titers. Within the HFP line, feather peckers tended to have less active responses compared to neutrals at adolescent age, while victims had more active responses compared to the other phenotypes at adult age. Feather peckers had higher 5-HT levels than neutrals at adult age. Behavioral and CORT responses to MR were not consistent over time, suggesting that responses to MR might not reflect coping style in this study. Furthermore, proactive behavioral responses were correlated with reactive physiological measures and vice versa. Thus, it was not possible to categorize FP genotypes or FP phenotypes into specific coping styles

Stress response, peripheral serotonin and natural antibodies in feather pecking genotypes and phenotypes and their relation with coping style

Feather pecking (FP), a serious welfare and economic issue in the egg production industry, has been related to coping style. Proactive and reactive coping styles differ in, among others, the stress response, serotonergic activity and immune activity. Yet, it is unknown whether genetic lines divergently selected on FP (i.e. FP genotypes) or individuals differing in FP (i.e. FP phenotypes) can be categorized into coping styles. Therefore, we determined peripheral serotonin (5-HT) levels, natural antibody (NAb) titers, behavioral and corticosterone (CORT) responses to manual restraint (MR) in FP genotypes (high FP (HFP), low FP (LFP) and unselected control (CON) line) and FP phenotypes (feather pecker, feather pecker-victim, victim and neutral). We further examined the consistency of and relationships between behavioral and physiological measures. FP genotypes differed in behavioral responses to MR, 5-HT levels and NAb titers, but not in CORT levels after MR. HFP birds had less active responses at adolescent age, but more active responses at adult age compared to LFP and CON birds. The CON line had higher 5-HT levels at adolescent age, while the HFP line had lower 5-HT levels than the other lines at adult age. Overall, the HFP line had lower IgM NAb titers, while the LFP line had lower IgG NAb titers compared to the other lines. FP phenotypes differed in behavioral responses to MR and 5-HT levels, but not in CORT levels after MR or NAb titers. Within the HFP line, feather peckers tended to have less active responses compared to neutrals at adolescent age, while victims had more active responses compared to the other phenotypes at adult age. Feather peckers had higher 5-HT levels than neutrals at adult age. Behavioral and CORT responses to MR were not consistent over time, suggesting that responses to MR might not reflect coping style in this study. Furthermore, proactive behavioral responses were correlated with reactive physiological measures and vice versa. Thus, it was not possible to categorize FP genotypes or FP phenotypes into specific coping styles

Feather pecking genotype and phenotype affect behavioural responses of laying hens

Feather pecking (FP) is a major welfare and economic issue in the egg production industry. Behavioural characteristics, such as fearfulness, have been related to FP. However, it is unknown how divergent selection on FP affects fearfulness in comparison to no selection on FP. Therefore, we compared responses of birds selected on low (LFP) and high feather pecking (HFP) with birds from an unselected control line (CON) to several behavioural tests (i.e. novel object (NO), novel environment (NE), open field (OF) and tonic immobility (TI)) at young and adult ages. Furthermore, the relation between actual FP behaviour (i.e. FP phenotypes) and fearfulness is not well understood. Therefore, we compared responses of birds with differing FP phenotypes. Feather pecking phenotypes of individual birds were identified via FP observations at several ages. The number of severe feather pecks given and received was used to categorize birds as feather peckers, feather pecker-victims, victims or neutrals. Here we show that HFP birds repeatedly had more active responses (i.e. they approached a NO sooner, vocalized sooner and more, showed more flight attempts and had shorter TI durations), which could indicate lower fearfulness, compared to CON and LFP birds at both young and adult ages. Within the HFP line, feather peckers had more active responses (i.e. they tended to show more flight attempts compared to victims and tended to walk more compared to neutrals), suggesting lower fearfulness, compared to victims and neutrals. Thus, in this study high FP seems to be related to low fearfulness, which is opposite to what previously has been found in other experimental and commercial lines. This stresses the need for further research into the genetic and phenotypic correlations between FP and fearfulness in various populations of chickens, especially in commercial lines. Findings from experimental lines should be used with caution when developing control and/or prevention methods that are to be applied in commercial settings. Furthermore, activity and/or coping style might overrule fearfulness within the HFP line, as HFP birds and feather peckers within the HFP line had more active responses. This might indicate a complex interplay between fearfulness, activity and coping style that could play a role in the development of FP.</p

High and low feather pecking selection lines of laying hens differ in response to a judgment bias test

Feather pecking represents a serious problem in the poultry industry that can negatively affect production as well as the welfare of laying hens. Although feather pecking has been studied from many different angles, there are only a few studies of the relationship between feather pecking and cognition. This study aims to compare the cognitive performance of hens from the high feather pecking (HFP) and the low feather pecking (LFP) lines in a visual discrimination (Go/No-Go) task and to study their decision making under ambiguity using the judgment bias test. Twenty HFP and 20 LFP hens were trained in a visual discrimination task to approach a coloured feeder (white for half of the hens and black for the other half) containing a reward (one mealworm) and to refrain from approaching a feeder with a different colour (colour opposite to positive, i.e. black or white) to avoid punishment (water spraying). During the subsequent judgment bias tests hens were tested in the presence of the positive, negative or ambiguous stimulus (grey coloured feeder), always one type of stimulus at a time. The latencies to reach each of the stimuli were recorded. At the end of the visual discrimination training phase, 36 out of 40 hens successfully discriminated the positive and the negative coloured feeder. There was a slower association of the coloured feeder with the reward in the HFP line and HFP hens did not suppress the response to the negative stimulus as effective as HFP hens, which could be a sign of their high motor impulsiveness. However, in the judgment bias test HFP hens approached the ambiguous feeder significantly faster than LFP hens (HFP 13.59 ± 1.11 s, LFP 16.68 ± 1.10 s, P < 0.05), that can be interpreted as evidence that hens from the HFP line are more optimistic, i.e. that they are in a more positive affective state. The high motor impulsiveness of HFP hens provides another possible explanation for their response to the ambiguous stimulus. However, higher motor activity of the HFP line did not affect the results of the judgment bias test. Furthermore, there were no significant differences in plasma corticosterone levels between the lines, suggesting that differences in stress levels might not explain the results of the judgment bias test.</p

Fast- and slower-growing broilers respond similarly to a reduction in stocking density with regard to gait, hock burn, skin lesions, cleanliness, and performance

ABSTRACT: There is an increasing trend toward broiler production systems with higher welfare requirements. Breed and stocking density are considered key factors for broiler welfare that are often specified as criteria for such higher welfare systems. However, it remains unknown how slower-growing broilers respond to a reduction in stocking density with regard to their welfare and performance, and whether this response differs from fast-growing broilers. Therefore, we compared fast- (F) and slower-growing broilers (S) housed at 4 different stocking densities (24, 30, 36, and 42 kg/m2, based on slaughter weight) and measured their welfare scores (i.e., gait, footpad dermatitis, hock burn, skin lesions and cleanliness), litter quality and performance. The experiment had a 2 × 4 factorial design with 4 replicates (pens) per treatment (32 pens in total). Thinning (15%) was done in a 50/50 male/female ratio at 38 (F) and 44 (S) d of age (estimated body weight of 2.2 kg). We hypothesized that breeds would respond differently to a reduction in stocking density. Contrary to our hypothesis, only one interaction between breed and stocking density was found on footpad dermatitis, indicating that fast- and slower-growing broilers generally showed similar responses to a reduction in stocking density. F broilers showed a steeper decline in the prevalence of footpad dermatitis with reducing stocking density compared to S broilers. Broilers housed at lower stocking densities (24 and/or 30 kg/m2) showed improved welfare measures, litter quality and performance compared to those housed at higher stocking densities (36 and/or 42 kg/m2). S broilers had better welfare scores (gait, footpad dermatitis and skin lesions), litter quality and lower performance compared to F broilers. In conclusion, reducing stocking density improved welfare of both F and S broilers, but more for F broilers in case of footpad dermatitis, and using S broilers improved welfare compared to F broilers. Reducing stocking density and using slower-growing broilers benefits broiler welfare, where combining both would further improve broiler welfare

Chicken lines divergently selected on feather pecking differ in immune characteristics

It is crucial to identify whether relations between immune characteristics and damaging behaviors in production animals exist, as these behaviors reduce animal welfare and productivity. Feather pecking (FP) is a damaging behavior in chickens, which involves hens pecking and pulling at feathers of conspecifics. To further identify relationships between the immune system and FP we characterized high FP (HFP) and low FP (LFP) selection lines with regard to nitric oxide (NO) production by monocytes, specific antibody (SpAb) titers, natural (auto)antibody (N(A)Ab) titers and immune cell subsets. NO production by monocytes was measured as indicator for innate pro-inflammatory immune functioning, SpAb titers were measured as part of the adaptive immune system and N(A)Ab titers were measured as they play an essential role in both innate and adaptive immunity. Immune cell subsets were measured to identify whether differences in immune characteristics were reflected by differences in the relative abundance of immune cell subsets. Divergent selection on FP affected NO production by monocytes, SpAb and N(A)Ab titers, but did not affect immune cell subsets. The HFP line showed higher NO production by monocytes and higher IgG N(A)Ab titers compared to the LFP line. Furthermore the HFP line tended to have lower IgM NAAb titers, but higher IgM and IgG SpAb titers compared to the LFP line. Thus, divergent selection on FP affects the innate and adaptive immune system, where the HFP line seems to have a more responsive immune system compared to the LFP line. Although causation cannot be established in the present study, it is clear that relationships between the immune system and FP exist. Therefore, it is important to take these relationships into account when selecting on behavioral or immunological traits