Social Reinstatement Research Articles

Increased temperature during incubation increases the sociality of male broilers in later life

Egg incubation through artificial means is a highly controlled process, where eggs are held at a fixed air temperature of 37.6 °C. Nevertheless, much research has been conducted on alternative temperature profiles to evaluate their influence on production and welfare traits. Most attention has been paid on increasing temperature as this has been shown to improve heat tolerance in later life. Limited research has been conducted on the effects on animal behavior, although the absence of negative emotions such as fearfulness and the presence of social expression is considered crucial for positive animal welfare as stated by the Welfare Quality® Protocol for Poultry. Therefore, the objective of the current study was to investigate the effect of two heat tolerance improving thermal treatments: (T1, +1 °C and T2, +2 °C from embryonic day 15–20) on fearful and social behaviors in later life. A total of 12 pens (4 per treatment) containing 13–14 chickens was reared for 42 days. During this rearing period, post-hatch fearful and social behavior were quantified using seven behavioral tests: an emergence test, a social reinstatement test, an isolation test, a novel arena test, a novel object test, a human stationary and a human approach test. These tests were chosen based on a thorough literature study and repeated 2 or 3 times. The research results showed that social behaviors were affected by the interaction of treatment and gender. Whereas in standard incubation, males have a lower social reinstatement tendency, both treatments changed their behavior. T1 males vocalized more than females during isolation (males: 73 ± 4 calls versus females: 38 ± 2 calls, P < 0.001) and T2 males showed more social motivation during a social reinstatement test compared to C (T2: 121 ± 20 s versus C: 66 ± 25 s, P < 0.05) and T1 (57 ± 27 s, P < 0.05). Finally, an effect of age was found with older birds being less fearful of a novel object and novel environment, but more fearful of an approaching human. Also, they seem more socially driven to contact conspecifics. However, the validity of these age results is questionable as habituation, changing sensory and/or cognitive skills, variance between repeats and possible reduced mobility at an older age could affect the behavioral response over time. In conclusion, increased temperature during incubation conditions can improve heat tolerance in later life, however, sociality is also affected. Both T1 and T2 changed social behaviour. An increased tendency to reinstate contact with conspecifics is found in T2 males than females.

Early life environment affects behavior, welfare, gut microbiome composition, and diversity in broiler chickens.

This study aimed to identify whether early-life conditions in broiler chickens could affect their behavior and welfare, and whether or not this was associated with an altered gut microbiome composition or diversity. Broilers were tested in a 2 x 2 factorial design with hatching conditions [home pen (OH) or at the hatchery (HH)] and enrichment (dark brooder (EE) or no brooder (NE) until 14 days of age) as factors (N = 6 per treatment combination). Microbiota composition was measured in the jejunum on days (d) 7, 14, and 35 and in pooled fecal samples on day 14. A novel environment test (NET) was performed on days 1 and 11, and the behavior was observed on days 6, 13, and 33. On day 35, composite asymmetry was determined and footpad dermatitis and hock burn were scored. In their home pen, HH showed more locomotion than OH (P = 0.05), and NE were sitting more and showed more comfort behavior than EE at all ages (P <0.001 and P = 0.001, respectively). On days 6 and 13 NE showed more eating and litter pecking while sitting, but on day 33 the opposite was found (age*enrichment: P = 0.05 and P <0.01, respectively). On days 1 and 11, HH showed more social reinstatement in the NET than OH, and EE showed more social reinstatement than NE (P <0.05). Composite asymmetry scores were lower for EE than NE (P <0.05). EE also had less footpad dermatitis and hock burn than NE (P <0.001). Within OH, NE had a more diverse fecal and jejunal microbiome compared to EE on day 14 (feces: observed richness: P = 0.052; jejunum: observed richness and Shannon: P <0.05); the principal component analysis (PCA) showed differences between NE and EE within both HH and OH in fecal samples on day 14, as well as significant differences in bacterial genera such as Lactobacillus and Lachnospiraceae (P <0.05). On day 35, PCA in jejunal samples only showed a trend (P = 0.068) for differences between NE vs. EE within the OH. In conclusion, these results suggest that especially the dark brooder affected the behavior and had a positive effect on welfare as well as affected the composition and diversity of the microbiome. Whether or not the behavior was modulated by the microbiome or vice versa remains to be investigated.

Exploring animal genetic resources of the domestic chicken and their behavior in the open field

Animal welfare is of general interest, and in the farming arena, efforts have increased to create optimal conditions for poultry production. Detailed and standardized studies on specific behavioral issues, such as fear, exploration, and social reinstatement behavior, are needed to support these initiatives. The variables mentioned can be directly queried from the animal in the open field to provide information on welfare-related behavioral traits, such as general fearfulness and balanced emotionality. Animal genetic resources help us get an insight into the possible diversity of behavioral responses. The majority of these responses can be identified as breed-specific and thus genetically correlated, providing a starting point for future breeding objectives. The behavioral responses of a chicken can be related to the breeding history of the population or to the experience gained during its lifetime. Both may go hand in hand to enable the animal to adapt to its environment, contributing to animal welfare.

Effect of lower temperature stimuli during incubation on fear and social-related behaviours in broilers

Temperature is the most influential environmental parameter during egg incubation affecting embryo development, hatchability and post-hatch performance of broilers. Industrial incubation operates to control the temperature and humidity around the eggs closely based on predefined setpoints and keep fluctuations to a minimum. On the other hand, during brooding, the mother hen regularly leaves the nest for self-maintenance resulting in a striking difference between the constant industrial versus fluctuating natural incubation temperature profiles. Previous studies on ducks and laying hens have found fear and/or social behaviours to be affected by temperatures below recommended values during incubation, a similar result could be existing in commercial broilers. Therefore, this study examines the effect of lowering machine temperatures during incubation on behaviour. Three incubation treatments were defined with a constant machine temperature of 37.6 °C on embryonic day (ED) 0–13 and 19–21 with the machine temperature differing on ED 13–18: (1) Control (C; 37.6 °C), (2) non-optimal Incubation Treatment (IT; 36.6 °C), (3) Natural Treatment (NT, 30 °C for 30 min per day). Post-hatch fear and social behaviour were quantified using six scientifically accepted behavioural tests: three fear tests (novel object on day (d) 1 and d8, tonic immobility (d40), inversion (d42)), two social tests (isolation (d19) and social reinstatement (25)) and one social/fear test (emergence (d18 and d20)). For the emergence test, wherein the time taken for an individual chick to emerge from a T-shaped box was measured, a treatment effect was found on the latency to emerge (P < 0.05) with C chicks emerging more often and faster than IT chicks. As no differences for IT were found in other social tests, the emergence suggest IT chicks to be more hesitant towards novel environments. No differences were present between NT and C or NT and IT. For the isolation test, where an individual chick is visually and audibly isolated for 3 min and the number of vocalisations was measured, an interaction was found between treatment and sex (P < 0.001). Females vocalised more than males in IT and C, but this was not the case for NT. NT male chicks could thus be considered more sensitive to social separation, which could be explained by the higher impact of early stress, caused by the severe temperature drops in NT, having a stronger impact on the anxiety behaviour of males compared to females in later life.

Attraction for familiar conspecifics in young chicks (Gallus gallus): An interbreed study

From the beginning of life, discriminating between familiar and unfamiliar individuals and staying in contact with conspecifics are important to establish social relationships. To better understand these early social behaviours, we studied the different responses to familiar/unfamiliar individuals in 4-day-old domestic chicks (Gallus gallus) in three genetically isolated breeds: Padovana, Polverara and Robusta maculata. Chicks discriminated between familiar and unfamiliar individuals, staying closer to familiar individuals. Social reinstatement and fear responses were measured as the average distance between subjects, the latency of the first step and exploration of the arena differed between breeds. More socially motivated chicks, that stayed in closer proximity, were less afraid of starting to move and explored the environment more extensively. Interbreed differences in social reinstatement indicate that social attraction shows genetic variability from the early stages of life.

Japanese quail classified by their permanence in proximity to a high or low density of conspecifics: a search for underpinning variables

Test of sociality in poultry is mainly based on the bird's individual ability to make quick social discriminations. In recent years, a density-related permanence (DRP) test has been developed that enables us to classify young birds (while in groups) according to their individual permanence in proximity to either a high or low density of conspecifics (HD or LD, respectively). Thus, the result of the classification depends not only on the bird's individual response but also on the outcome of the social interactions within the whole group. The birds' performance in DRP was associated with underlying differences in social responses of their individuals. Quails in homogeneous groups of LD residents responded with less compact groups and higher levels of agonistic interactions to the presence of an intruder and showed higher levels of agonistic interactions among cage-mates than the homogeneous groups of HD birds. An acute stressor also induced a higher corticosterone response in the LD birds than in their HD counterparts. The present study addressed the question of whether contrasting DRP performance by Japanese quail can also reflect underlying differences in fearfulness and social reinstatement responses. Thus, LD and HD categorized juvenile birds underwent one of the following tests: tonic immobility (TI), open-field (OF), or a one-way runway. Results showed that HD birds required more inductions and developed shorter responses (P ≤ 0.05) in the TI test and walked more, faster, and greater distances in the OF (P ≤ 0.05) than their LD counterparts. No differences between groups were found in short social reinstatement responses. The present findings suggest that underlying fearfulness is lower in the HD than in the LD birds. A reduced fearfulness could be regarded as an additional favorable trait of the HD-classified quail to cope with environmental challenging situations.

Psychological and Physiological Stress in Hens With Bone Damage.

Abnormalities in bone development in humans and non-humans can lead to impaired physical and psychological health; however, evidence is lacking regarding the role of individual psychosocial factors in the development of poor bone conditions. Addressing this lack of knowledge, we used low-productive laying hens (n = 93) and assessed behavioral responses to an open-field test [at 17, 18, 29, 33 weeks of age (wa)], an aerial predator test (at 39 wa), and a social reinstatement test (at 42 wa). Bone condition was assessed using a palpation technique on five occasions (at 16, 29, 33, 45, 58 wa), with half of the hens experiencing damage (deviations, fractures, or both) at 29 wa and all hens by 58 wa. Corticosterone (CORT) concentration in feathers (at 16, 33, 58 wa) and body weight (at 23, 47, 58 wa) were also investigated. We hypothesized that lighter birds (at 23 wa) with higher CORT (at 16 wa) and open field-induced fear collected before the onset of lay (at 17 and 18 wa) are associated with a worse bone condition when in lay. We also hypothesized that those birds with more damage at the peak of laying (at 29 wa) would be lighter at 47 and 58 wa and more fearful by showing higher open field-induced (at 29 and 33 wa) and predator-induced fear responses, however, acting less socially toward conspecifics. These hens were also expected to have higher CORT (at 33 and 58 wa). Our results show no association between open-field fear level and fear behavior, CORT concentration, or body weight on the one hand (all measured before starting to lay) and bone damage at 29 wa on the other. When in lay, bone damage was associated with more pecking and less crossing zones when faced with an open-field situation at 29 wa and improved sociality at 42 wa. This study provides the first evidence of a relationship of bone health with fear, sociality, and stress response. When in poor bone condition, our hens had enhanced psychological stress measured by fear behavior reactivity but not physiological stress measured as feather CORT concentration.

Genetic parameters for bone ash and phosphorus utilization in an F2 cross of Japanese quail

ABSTRACTThe main objective of this study was to perform quantitative genetic analyses of tibia and foot ash traits, which might serve as proxy traits to improve phosphorus utilization (PU) in a breeding program. Additionally, data for ash concentration in tibia and foot were compared with data for total amount of ash. Heritabilities for bone ash traits and genetic and phenotypic correlations between bone ash traits and PU were estimated. A total of 887 F2 birds, established from 2 Japanese quail lines divergently selected on social reinstatement behavior, were provided a P deficient diet. In a metabolic study, feed consumption was measured and total excreta collected for each bird separately. Afterwards, birds were euthanized, the bones obtained and incinerated. Bone ash data showed a heritability of 0.230 (amount of tibia ash) to 0.342 (amount of foot ash), which was higher than estimated for PU, P retention, calcium utilization (0.120–0.174), and performance traits (0.088–0.114). The strongest genetic and phenotypic correlations between PU and bone ash traits were detected for the amount of foot ash with 0.549 and 0.527, respectively. Genetic and phenotypic correlations were stronger between PU and ash amount than between PU and ash percentage, irrespective of bone. Therefore, ash amount was considered a better trait than ash percentage to reflect PU. Strong genetic and phenotypic correlations were detected between the amount of foot and tibia ash (0.887 and 0.901, respectively). Phenotypic and genetic correlations between ash amount and PU or calcium utilization were almost identical, irrespective of bone. Foot ash is as suitable as tibia ash, but easier to determine. Bone ash data, especially the amount of foot ash, seem to be suitable indirect selection criteria for P efficiency breeding.

Social reinstatement: a rat model of peer-induced relapse.

An important factor that can lead to drug relapse is to re-associate with drug-using social peers, but there is little literature on the effect of social peers on relapse in animal models. The current study used a dual-compartment operant conditioning apparatus that allowed adult male rats to respond for cocaine in the presence of a conspecific. In experiment 1, rats were trained to self-administer cocaine in the presence of a social peer that was separated by a wire screen partition and then that peer was used as a reinstatement cue following a period of extinction. In the next experiments, rats were trained on alternating sessions to self-administer cocaine in the presence of one peer and to self-administer saline in the presence of a different peer using either a single-active lever procedure (experiment 2) or a double-active lever procedure (experiment 3). Following extinction of responding in the absence of the peers, the effect of re-exposure to the cocaine- and saline-associated peers on reinstatement of drug seeking was determined. This was tested using both single- and double-active lever procedures. In experiment 1, a peer that was present throughout cocaine self-administration was able to reinstate cocaine seeking following a period of extinction. In experiments 2 and 3, drug seeking was reinstated by the cocaine-associated peer (S+), but not the saline-associated peer (S-). This discrimination occurred when using either the single-active lever procedure or double-active lever procedure. These results indicate that a social peer can be used as a discriminative stimulus to signal cocaine availability and that re-introduction of a peer previously paired with cocaine can reinstate cocaine seeking, confirming clinical reports that peer affiliation among abstinent cocaine users is an important determinant of relapse.

Environmental complexity buffers against stress-induced negative judgement bias in female chickens

Cognitive processes are often biased by emotions. In humans, affective disorders are accompanied by pessimistic judgement, while optimistic judgement is linked to emotional stability. Similar to humans, animals tend to interpret ambiguous stimuli negatively after experiencing stressful events, although the long-lasting impact on judgement bias has rarely been investigated. We measure judgement bias in female chicks (Gallus gallus domesticus) after exposure to cold stress, and before and after exposure to additional unpredictable stressors. Additionally, we explore if brain monoamines can explain differences in judgement bias. Chicks exposed to cold stress did not differ in judgement bias compared to controls, but showed sensitivity to additional stressors by having higher motivation for social reinstatement. Environmental complexity reduced stress-induced negative judgement bias, by maintaining an optimistic bias in individuals housed in complex conditions even after stress exposure. Moreover, judgement bias was related to dopamine turnover rate in mesencephalon, with higher activity in individuals that had a more optimistic response. These results demonstrate that environmental complexity can buffer against negative effects of additive stress and that dopamine relates to judgement bias in chicks. These results reveal that both internal and external factors can mediate emotionally biased judgement in animals, thus showing similarities to findings in humans.

Genetics and Genomics of Social Behavior in a Chicken Model.

The identification of genes affecting sociality can give insights into the maintenance and development of sociality and personality. In this study, we used the combination of an advanced intercross between wild and domestic chickens with a combined QTL and eQTL genetical genomics approach to identify genes for social reinstatement, a social and anxiety-related behavior. A total of 24 social reinstatement QTL were identified and overlaid with over 600 eQTL obtained from the same birds using hypothalamic tissue. Correlations between overlapping QTL and eQTL indicated five strong candidate genes, with the gene TTRAP being strongly significantly correlated with multiple aspects of social reinstatement behavior, as well as possessing a highly significant eQTL.

Laying hens performing gregarious nesting show less pacing behaviour during the pre-laying period

The phenomenon of gregarious nesting occurs when hens choose to enter and lay their eggs in a nest box which is already occupied by one or more hens, even when an empty nest box is also available. It has been suggested that inexperienced hens copy the nest selection preferences of experienced hens until their own preferences have developed. In addition, gregarious nesting has been found to be an anti-predator behaviour, indicating that fear may be a factor inducing gregarious nesting. Individual differences in sociality and dominance hierarchy may also be important factors. The aim of the current study was to investigate the relationship between the individual level of fearfulness, sociality and hierarchical dominance, and the performance of gregarious nesting behaviour in laying hens. Fifteen-week-old laying hens (Isa Warren, n = 180) were housed in groups of 15 individuals. At 20–21 weeks of age, nesting behaviour and agonistic interactions were recorded. Furthermore, behavioural tests reflecting fearfulness (tonic immobility and novel object tests) and sociality (social reinstatement test) were performed. Based on their choices of nest boxes (occupied v. unoccupied), the hens were classified as gregarious, solitary or intermediary nesters. A dominance hierarchy was formed based on the data on agonistic interactions. The results showed that intermediary nesters, i.e. those who visited both occupied and unoccupied nest boxes roughly equally often, performed significantly more pre-laying pacing behaviour compared to gregarious nesters (P = 0.028). There was no effect of categorisation of nesting behaviour (gregarious, solitary or intermediary nesters) on body weight, responses to tonic immobility test, novel object test, social reinstatement test or dominance hierarchy (P > 0.06). The results may suggest that intermediary nesters experience more frustration compared to hens that are predominantly gregarious nesters as indicated by the increased pre-laying pacing behaviour. Alternatively, the increased pre-laying pacing behaviour could be a reflection of a longer decision-making process in unexperienced hens. In light of these different possible explanations, the cause-and-effect relationship between frustration/stress and nesting behaviour remains to be assessed.

Social reinstatement: A rat model of peer-induced relapse

Social reinstatement: A rat model of peer-induced relapse

Effects of Divergent Selection for Fear of Humans on Behaviour in Red Junglefowl.

Domestication has caused a range of similar phenotypic changes across taxa, relating to physiology, morphology and behaviour. It has been suggested that this recurring domesticated phenotype may be a result of correlated responses to a central trait, namely increased tameness. We selected Red Junglefowl, the ancestors of domesticated chickens, during five generations for reduced fear of humans. This caused a marked and significant response in tameness, and previous studies have found correlated effects on growth, metabolism, reproduction, and some behaviour not directly selected for. Here, we report the results from a series of behavioural tests carried out on the initial parental generation (P0) and the fifth selected generation (S5), focusing on behaviour not functionally related to tameness, in order to study any correlated effects. Birds were tested for fear of humans, social reinstatement tendency, open field behaviour at two different ages, foraging/exploration, response to a simulated aerial predator attack and tonic immobility. In S5, there were no effects of selection on foraging/exploration or tonic immobility, while in the social reinstatement and open field tests there were significant interactions between selection and sex. In the aerial predator test, there were significant main effects of selection, indicating that fear of humans may represent a general wariness towards predators. In conclusion, we found only small correlated effects on behaviours not related to the tameness trait selected for, in spite of them showing high genetic correlations to fear of humans in a previous study on the same population. This suggests that species-specific behaviour is generally resilient to changes during domestication.

Post-retrieval extinction in adolescence prevents return of juvenile fear.

Traumatic experiences early in life can contribute to the development of mood and anxiety disorders that manifest during adolescence and young adulthood. In young rats exposed to acute fear or stress, alterations in neural development can lead to enduring behavioral abnormalities. Here, we used a modified extinction intervention (retrieval+extinction) during late adolescence (post-natal day 45 [p45]), in rats, to target auditory Pavlovian fear associations acquired as juveniles (p17 and p25). The effects of adolescent intervention were examined by assessing freezing as adults during both fear reacquisition and social transmission of fear from a cagemate. Rats underwent testing or training at three time points across development: juvenile (p17 or p25), adolescent (p45), and adult (p100). Retrieval+extinction during late adolescence prevented social reinstatement and recovery over time of fears initially acquired as juveniles (p17 and p25, respectively). Adolescence was the only time point tested here where retrieval+extinction prevented fear recall of associations acquired 20+ days earlier.

Effects of Isolation on Stress Responses to Novel Stimuli in Subadult Chickens (Gallus gallus)

AbstractExtensive research has examined the effects of social isolation in neonatal and adult animal populations, but few studies have examined the effect of social isolation in early adulthood. Animals reaching reproductive age often experience extensive social changes as they leave their natal site, and a social stressor like isolation may uniquely affect this age group. Furthermore, adolescence is a time when sex differences in behavior become more pronounced. As such, the effects of social stressors are likely to vary by sex. In this study, we used noninvasive methods to evaluate stress responses to social change in male and female subadult chickens (Gallus gallus). Half of the birds experienced regular sessions of social isolation over the course of 2 wk, while the other half were never isolated. Subsequently, all of the animals were exposed to a suite of three novel probes, including an open‐field test. We monitored the birds’ behavioral (head movements) and physiological (fecal glucocorticoid metabolites, FGM) response to the tests. Our results indicate that, for subadult chickens, the effect of social isolation is sex dependent: Male FGM and behavioral responses did not change with subsequent experiences, in contrast to females. Females also exhibited more social reinstatement behavior compared to males. Our results are consistent with the expectations of differences between the sexes based on changes in the social environment due to sex‐biased dispersal patterns. For both sexes, the FGM and behavioral responses varied independently, which highlights the necessity for multiple measures of stress in animal populations.

Growth heterogeneity in broiler breeder pullets is settled before the onset of feed restriction but is not predicted by size at hatch.

Uniform growth is a desirable trait in all large-scale animal production systems because it simplifies animal management and increases profitability. In parental broiler flocks, so-called broiler breeders, low growth uniformity is largely attributed to the feed competition that arises from quantitatively restricted feeding. As feed restriction is crucial to maintaining healthy and fertile breeders, several practices for reducing feed competition and the associated growth heterogeneity have been suggested and range from nutrient dilution by increasing fiber content in feed to intermittent fasting with increased portion size ("skip a day"), but no practice appears to be entirely effective. The fact that a large part of the heterogeneity remains even when feed competition is minimized suggests that some growth variation is caused by other factors. We investigated whether this variation arises during embryonic development (as measured by size at hatch) or during posthatch development by following the growth and body composition of birds of varying hatch sizes. Our results support the posthatch alternative, with animals that later grow to be small or large (here defined as >1 SD lighter or heavier than mean BW of the flock) being significantly different in size as early as 1 d after gaining access to feed ( < 0.05). We then investigated 2 possible causes for different postnatal growth: that high growth performance is linked 1) to interindividual variations in metabolism (as measured by cloacal temperature and verified by respirometry) or 2) to higher levels of social motivation (as measured in a social reinstatement T-maze), which should reduce the stress of being reared in large-scale commercial flocks. Neither of these follow-up hypotheses could account for the observed heterogeneity in growth. We suggest that the basis of growth heterogeneity in broiler breeder pullets may already be determined at the time of hatch in the form of qualitatively different maternal investments or immediately thereafter as an indirect result of differences in incubation conditions, hatching time, and resulting fasting time. Although this potential difference in maternal investment is not seen in body mass, tarsometatarsal length, or full body length of day-old chicks arriving at the farm, it may influence the development of differential feed and water intake during the first day of feeding, which in turn has direct effects on growth heterogeneity.

A medium density genetic map and QTL for behavioral and production traits in Japanese quail.

BackgroundBehavioral traits such as sociability, emotional reactivity and aggressiveness are major factors in animal adaptation to breeding conditions. In order to investigate the genetic control of these traits as well as their relationships with production traits, a study was undertaken on a large second generation cross (F2) between two lines of Japanese Quail divergently selected on their social reinstatement behavior. All the birds were measured for several social behaviors (social reinstatement, response to social isolation, sexual motivation, aggression), behaviors measuring the emotional reactivity of the birds (reaction to an unknown object, tonic immobility reaction), and production traits (body weight and egg production).ResultsWe report the results of the first genome-wide QTL detection based on a medium density SNP panel obtained from whole genome sequencing of a pool of individuals from each divergent line. A genetic map was constructed using 2145 markers among which 1479 could be positioned on 28 different linkage groups. The sex-averaged linkage map spanned a total of 3057 cM with an average marker spacing of 2.1 cM. With the exception of a few regions, the marker order was the same in Japanese Quail and the chicken, which confirmed a well conserved synteny between the two species. The linkage analyses performed using QTLMAP software revealed a total of 45 QTLs related either to behavioral (23) or production (22) traits. The most numerous QTLs (15) concerned social motivation traits. Interestingly, our results pinpointed putative pleiotropic regions which controlled emotional reactivity and body-weight of birds (on CJA5 and CJA8) or their social motivation and the onset of egg laying (on CJA19).ConclusionThis study identified several QTL regions for social and emotional behaviors in the Quail. Further research will be needed to refine the QTL and confirm or refute the role of candidate genes, which were suggested by bioinformatics analysis. It can be hoped that the identification of genes and polymorphisms related to behavioral traits in the quail will have further applications for other poultry species (especially the chicken) and will contribute to solving animal welfare issues in poultry production.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-014-1210-9) contains supplementary material, which is available to authorized users.

Plumage damage in free-range laying hens: Behavioural characteristics in the rearing period and the effects of environmental enrichment and beak-trimming

Severe feather-pecking, whereby birds peck at and pull out the feathers of other birds, is one of the greatest welfare concerns and the most prevalent behavioural problem in laying hens. It can be extremely difficult to control, especially in non-cage laying flocks. Despite a multitude of studies on the topic, the principal underlying causes remain unclear and not much is known about why certain birds are affected more than others. Literature suggests that rearing is an important period for the development of behaviours later in life. Although severe feather-pecking is not usually a welfare concern in the rearing period, behavioural tests when performed early in life may be predictive of plumage damage due to severe feather-pecking in adulthood. This experiment aimed to investigate whether behavioural tests during the rearing period could be predictive of plumage damage later in life. Sixteen pens of 50 ISA Brown laying hens were used, with four birds per pen selected at random as focal birds. Focal birds were subjected to behavioural tests during the rearing period including the open-field test, tonic immobility test and tests for a novel food reward. Two treatments, beak-trimming and environmental enrichment, were applied in a 2×2 factorial arrangement in rearing. The non-trimmed birds vocalised more (P=0.02, 91.5 vs. 83.6%) and at louder volumes (P=0.02, 71.4 vs. 47.0% of vocalisations categorised as loud rather than soft or silent) in the open-field test at 5 weeks of age. There was no difference between treatments in duration of tonic immobility (P=0.99). Non-trimmed birds exhibited more plumage damage at 43 weeks of age (P<0.001, 5.2 vs. 72.9% of birds with feather loss or wounds). Ordinal regression with treatments and treatment interactions as fixed effects and pens and blocks (sides of the shed) as random effects indicated no significant associations between behavioural test reactions and plumage damage (all P>0.1). Thus while beak-trimmed birds made fewer vocalisations in an open-field test and had less plumage damage in adulthood as expected, there is no evidence that reactions to the behavioural tests were predictive of plumage damage. Instead, results indicate that environmental enrichment affected bird behaviour during the rearing period but did not affect plumage damage due to severe feather-pecking later in life. The test responses including more vocalisations in the open-field test, but no difference in the tonic immobility responses, indicate that the differences may be due to motivation for social reinstatement rather than fearfulness.

Maternally derived egg hormones, antibodies and antimicrobial proteins: common and different pathways of maternal effects in Japanese quail.

Avian eggs contain a variety of maternally-derived substances that can influence the development and performance of offspring. The levels of these egg compounds vary in relation to environmental and genetic factors, but little is known about whether there are correlative links between maternal substances in the egg underlying common and different pathways of maternal effects. In the present study, we investigated genetically determined variability and mutually adjusted deposition of sex hormones (testosterone-T, androstenedione-A4 and progesterone-P4), antibodies (IgY) and antimicrobial proteins (lysozyme) in eggs of Japanese quail (Coturnix japonica). We used different genetic lines that were independently selected for yolk T concentrations, duration of tonic immobility and social reinstatement behaviour, since both selections for behavioural traits (fearfulness and social motivation, respectively) produced considerable correlative responses in yolk androgen levels. A higher selection potential was found for increased rather than decreased yolk T concentrations, suggesting that there is a physiological minimum in egg T levels. Line differences in yolk IgY concentrations were manifested within each selection experiment, but no consistent inter-line pattern between yolk IgY and T was revealed. On the other hand, a consistent inverse inter-line pattern was recorded between yolk IgY and P4 in both selections for behavioural traits. In addition, selections for contrasting fearfulness and social motivation were associated with changes in albumen lysozyme concentrations and an inverse inter-line pattern between the deposition of yolk IgY and albumen lysozyme was found in lines selected for the level of social motivation. Thus, our results demonstrate genetically-driven changes in deposition of yolk T, P4, antibodies and albumen lysozyme in the egg. This genetic variability can partially explain mutually adjusted maternal deposition of sex hormones and immune-competent molecules but the inconsistent pattern of inter-line differences across all selections indicates that there are other underlying mechanisms, which require further studies.