Early and late cognitive and behavioral aspects associated with range use in free-range laying hens (Gallus gallus domesticus).

Individual differences in free-range chicken systems are important factors influencing how birds use the range (or not), even if individuals are reared in the same environmental conditions. Here, we investigated how various aspects of the birds' behavioral and cognitive tendencies, including their optimism/pessimism, cognitive flexibility, sociability, and exploration levels, are associated with range use and how they may change over time (before and after range access). To achieve this, 100 White Leghorn laying hen chicks underwent three distinct behavioral/cognitive tests-the cognitive bias test, the detour test, and the multivariate test-prior to gaining access to the range, between 9 and 39 days of age. After range access was allowed (from day 71), birds' range use was evaluated over 7 nonconsecutive days (from 74-91 days of age). Subsequently, a subset of birds, classified as high rangers (n = 15) and low rangers (n = 15) based on their range use, underwent retesting on the same three previous tests between 94 and 108 days of age. Our results unveiled a negative correlation trend between birds' evaluation of the ambiguous cue and their subsequent range use (rho = -0.19, p = 0.07). Furthermore, low rangers were faster to learn the detour task (χ2 = 7.34, df = 1, p = 0.006), coupled with increased sociability during the multivariate test (rho = -0.23, p = 0.02), contrasting with their high-ranging counterparts, who displayed more exploratory behaviors (F[1,27] = 3.64, p = 0.06). These behavioral patterns fluctuated over time (before and after range access); however, conclusively attributing these changes to birds' aging and development or the access to the range remains challenging. Overall, our results corroborate that behavioral and cognitive individual differences may be linked to range use and offer novel perspectives on the early behavioral and cognitive traits that may be linked to range use. These findings may serve as a foundation for adapting environments to meet individual needs and improve animal welfare in the future.

High-throughput phenotyping to characterise range use behaviour in broiler chickens.

A key characteristic of free-range chicken farming is to enable chickens to spend time outdoors. However, each chicken may use the available areas for roaming in variable ways. To check if, and how, broilers use their outdoor range at an individual level, we need to reliably characterise range use behaviour. Traditional methods relying on visual scans require significant time investment and only provide discontinuous information. Passive RFID (Radio Frequency Identification) systems enable tracking individually tagged chickens' when they go through pop-holes; hence, they only provide partial information on the movements of individual chickens. Here, we describe a new method to measure chickens' range use and test its reliability on three ranges each containing a different breed. We used an active RFID system to localise chickens in their barn, or in one of nine zones of their range, every 30 seconds and assessed range-use behaviour in 600 chickens belonging to three breeds of slow- or medium-growing broilers used for outdoor production (all <40 g daily weight gain). From those real-time locations, we determined five measures to describe daily range use: time spent in the barn, number of outdoor accesses, number of zones visited in a day, gregariousness (an index that increases when birds spend time in zones where other birds are), and numbers of zone changes. Principal Component Analyses (PCAs) were performed on those measures, in each production system, to create two synthetic indicators of chickens' range use behaviour. The first two PCA axes represented over 90% of the variance of the five measures and were both consistent over time and correlated with independent visual scans. Contributions of the five measures to the PCAs were similar among breeds, except for the correlation between the number of outdoor accesses and the four other measures. PC1 correlated with time spent inside the barn and zone changes frequency, whilst PC2 was explained by exploration of the range. Taken together, PC1 and PC2 indicators showed that range use increased with age, outdoor temperature (in spring), and did not differ between males and females. Importantly, daily scores for both indicators were repeatable among individuals - particularly in PC1 - showing inter-individual variability on range-use. The characterisation of broiler behaviour around their range with these reliable and repeatable indicators provides novel tools to help understand individual variations of range-use in free-range farming.

Welfare issues and potential solutions for laying hens in free range and organic production systems: A review based on literature and interviews.

In free-range and organic production systems, hens can make choices according to their needs and desires, which is in accordance with welfare definitions. Nonetheless, health and behavioral problems are also encountered in these systems. The aim of this article was to identify welfare challenges observed in these production systems in the EU and the most promising solutions to overcome these challenges. It is based on a review of published literature and research projects complemented by interviews with experts. We selected EU specific information for welfare problems, however, the selected literature regarding solutions is global. Free range use may increase the risk of infection by some bacteria, viruses and parasites. Preventive methods include avoiding contamination thanks to biosecurity measures and strengthening animals' natural defenses against these diseases which can be based on nutritional means with new diet components such as insect-derived products, probiotics and prebiotics. Phytotherapy and aromatherapy can be used as preventive and curative medicine and vaccines as alternatives to antibiotics and pesticides. Bone quality in pullets and hens prevents keel deviations and is favored by exercise in the outdoor range. Free range use also lead to higher exposure to variable weather conditions and predators, therefore shadow, fences and guard animals can be used to prevent heat stress and predation respectively. Granting a free range provides opportunities for the expression of many behaviors and yet many hens usually stay close to the house. Providing the birds with trees, shelters or attractive plants can increase range use. Small flock sizes, early experiences of enrichment and personality traits have also been found to enhance range use. Severe feather pecking can occur in free range production systems, although flocks using the outdoor area have better plumage than indoors. While many prevention strategies are facilitated in free range systems, the influence of genetics, prenatal and nutritional factors in free range hens still need to be investigated. This review provides information about practices that have been tested or still need to be explored and this information can be used by stakeholders and researchers to help them evaluate the applicability of these solutions for welfare improvement.

Positive effects of bubbles as a feeding predictor on behaviour of farmed rainbow trout.

Occupational enrichment emerges as a promising strategy for improving the welfare of farmed animals. This form of enrichment aims to stimulate cognitive abilities of animals by providing them with more opportunities to interact with and control their environment. Predictability of salient daily events, and in particular predictability of feeding, is currently one of the most studied occupational enrichment strategies and can take several forms. In fish, while temporal predictability of feeding has been widely investigated, signalled predictability (based on a signal, such as light or sound) has received little attention. Depending on the type of predictability used and the ecology of the species, the effects on fish welfare often differ. The present study aimed to determine which feeding predictability would be most appropriate for rainbow trout, the main continental farmed fish in Europe, and what the consequences might be for their welfare. We tested four feeding predictability conditions: temporal (based on time of day), signalled (based on bubble diffusion), temporal + signalled (based on time and bubble diffusion), and unpredictable (random feeding times). Behavioural and zootechnical outcomes recorded were swimming activity, aggressive behaviours, burst of accelerations, and jumps, emotional reactivity, and growth. Our results showed that rainbow trout can predict daily feedings relying on time and/or bubbles as predictors as early as two weeks of conditioning, as evidenced by their increased swimming activity before feeding or during feed omission tests, which allowed to reinforce their conditioned response. Temporal predictability alone resulted in an increase in pre-feeding aggressive behaviours, burst of accelerations, and jumps, suggesting that the use of time as the sole predictor of feedings in husbandry practices may be detrimental to fish welfare. Signalled predictability with bubbles alone resulted in fewer pre-feeding agonistic behaviours, burst of accelerations, and jumps than in the temporal predictability condition. The combination of temporal and signalled predictability elicited the highest conditioned response and the level of pre-feeding aggression behaviours, burst of accelerations and jumps tended to be lower than for temporal predictability alone. Interestingly, fish swimming activity during bubble diffusion also revealed that bubbles were highly attractive regardless of the condition. Rainbow trout growth and emotional reactivity were not affected by the predictability condition. We conclude, therefore, that the use of bubbles as a feeding predictor could represent an interesting approach to improve rainbow trout welfare in farms, by acting as both an occupational and physical enrichment.

White Leghorn and Red Junglefowl female chicks use distal and local cues similarly, but differ in persistency behaviors, during a spatial orientation task.

Although there is evidence to suggest that animal domestication acts as a modulator of spatial orientation, little is known on how domesticated animals, compared to their wild counterparts, orientate themselves when confronted to different environmental cues. Here, using domesticated White Leghorn chicks, and their ancestor, the Red Junglefowl (Gallus gallus), our main objective was to investigate how bird domestication influences the use of distal and local cues, during an orientation task. We also investigated the memory retention of these cues over time, and how persistent/flexible individuals from both breeds were at pecking at unreachable mealworms. Our results showed that the breeds did not differ in their use of distal or local cues, with both showing a marked preference for the use of local cues over distal ones. Over time, individual performance declined, but this was not influenced by the type of cue present during the tests, nor by the breed. Domesticated chicks showed greater signs of persistency compared to their wild conspecifics. In conclusion, domestication did not seem to alter how birds orientate spatially, but may have caused more subtle changes, such as an increase in behavioral persistency, a feature that may be adaptative in human-controlled and homogenous environments.

Foraging Behavior Shows Individual-Consistency Over Time, and Predicts Range Use in Slow-Growing Free-Range Male Broiler Chickens.

Recent research on free-range chickens shows that individual behavioral differences may link to range use. However, most of these studies explored individual behavioral differences only at one time point or during a short time window, assessed differences when animals were out of their social group and home environment (barn and range), and in specific tests or situations. Therefore, it is yet unclear how different behaviors relate to range use and how consistent these behaviors are at the individual level. To fill this gap, we here aimed to describe the behavioral budget of slow-growing male broiler chickens (S757N) when in their social group and home environment during the whole rearing period (from the second week of life to the twelfth week, before slaughter), and to relate observed behavioral differences to range use. For this, we followed a sample of individuals in two flocks (n = 60 focal chickens out of 200 chickens per flock), over two seasons, during three periods: before range access (from 14 to 25 days old), during early range access (first weeks of range access, from 37 to 53 days old), and during late range access (last weeks of range access, from 63 to 87 days old). By the end of each period, individual tests of exploration and social motivation were also performed, measuring exploration/activity and sociability propensities. Our results show that foraging (i.e., pecking and scratching at the ground) was the only behavior that correlated to range use for all three rearing periods, independent of the season. Foraging was also the only behavior that showed within-individual consistency from an early age and across the three rearing periods. Foraging may, therefore, serve as a useful behavioral predictor of range use in free-range broiler chickens. Our study increases the knowledge of how behaviors develop and relate to each other in a domesticated and intensely selected species, and improves our understanding of the biology of free-range broiler chickens. These findings can, ultimately, serve as a foundation to increase range use and improve chicken welfare.

Working for food is related to range use in free-range broiler chickens.

When animals prefer to make efforts to obtain food instead of acquiring it from freely available sources, they exhibit what is called contrafreeloading. Recently, individual differences in behavior, such as exploration, were shown to be linked to how prone an individual may be to contrafreeload. In this work, our main objective was to test whether and how individual differences in range use of free-range broiler chickens (Gallus gallus domesticus) were related to the individual motivation to contrafreeload. We also verified whether other behavioral variations could relate to range use. To that aim, over three different periods (before range access, first weeks of range access, and last weeks of range access), chickens with different ranging levels (low and high rangers) were submitted to a contrafreeloading test and had different behaviors recorded (such as foraging, resting, locomotion) in their home environment. During the contrafreeloading test, chickens were conditioned to one chamber presenting a foraging substrate and mealworms, while in the other chamber, mealworms were freely available on the floor. During testing trials, chickens had access to both empty chambers, and the time spent in each chamber was quantified. On average, low rangers preferred the chamber where mealworms were easily accessible (without the foraging substrate), while high rangers preferred the chamber where mealworms were accessible with difficulty, showing greater contrafreeloading. Out of ten behaviors recorded in chickens' home environment, foraging was the only one that differed significantly between our two ranging groups, with low rangers foraging, on average, significantly less than high rangers. These results corroborate previous experiences suggesting that range use is probably linked to chickens' exploratory trait and suggest that individual differences in free-range broiler chickens are present even before range access. Increasing our knowledge of individual particularities is a necessary step to improve free-range chicken welfare on the farm.

Rainbow trout discriminate 2-D photographs of conspecifics from distracting stimuli using an innovative operant conditioning device.

Cognitive abilities were studied in rainbow trout, the first continental fish production in Europe. Increasing public concern for the welfare of farmed-fish species highlighted the need for better knowledge of the cognitive status of fish. We trained and tested 15 rainbow trout with an operant conditioning device composed of self-feeders positioned in front of visual stimuli displayed on a screen. The device was coupled with a two-alternative forced-choice (2-AFC) paradigm to test whether rainbow trout can discriminate 2-D photographs of conspecifics (S+) from different visual stimuli (S-). The S- were applied in four stages, the last three stages representing increasing discrimination difficulty: (1) blue shapes; (2) black shape (star); (3) photograph of an object (among a pool of 60); (4) photograph of another fish species (among a pool of 60). Nine fish (out of 15) correctly managed to activate the conditioning device after 30-150 trials. The rainbow trout were able to discriminate images of conspecifics from an abstract shape (five individuals out of five) or objects (four out of five) but not from other fish species. Their ability to learn the category "fish shape" rather than distinguishing between conspecifics and heterospecifics is discussed. The successful visual discrimination task using this complex operant conditioning device is particularly remarkable and novel for this farmed-fish species, and could be exploited to develop cognitive enrichments in future farming systems. This device can also be added to the existing repertoire of testing devices suitable for investigating cognitive abilities in fish.

Social motivation and the use of distal, but not local, featural cues are related to ranging behavior in free-range chickens (Gallus gallus domesticus).

Animals can navigate an environment relying on different sources of information, such as geometrical or featural cues. The favoring of one type of information over another depends on multiple factors, such as inter-individual differences in behavior and cognition. Free-range chickens present different range use patterns, which may be explained by behavioral and cognitive differences. However, how behavior, cognition, and range use intercorrelate is still poorly understood. In this work, we aimed to further understand possible differences in behavior and cognition between two groups of free-range broiler chickens: those who frequently explore their range ('high rangers') and those who prefer to stay in or near the barn ('low rangers'). Prior to range access, individual behavior was measured in open field-, emergence-, and social motivation tests. To investigate cognitive differences, we analyzed whether exploratory behavior was linked to different performances in the use of distal and local spatial cues during an orientation task. During the social motivation test, low rangers showed a higher inclination to be near conspecifics than did high rangers. Our orientation tests show that chickens preferred to orientate themselves using the local cues over the distal cues. Individual differences were only found for distal, but not for local, cue use suggesting that demanding tasks are more efficient in revealing individual cognitive differences. Our results suggest that considering variation in social motivation may allow a more comprehensive understanding of chicken range use. Our results also support the importance of incorporating multiple aspects of individual differences to understand individual reactions to its environment.

Uninhibited chickens: ranging behaviour impacts motor self-regulation in free-range broiler chickens (Gallus gallus domesticus).

Inhibiting impulsive, less flexible behaviours is of utmost importance for individual adaptation in an ever-changing environment. However, problem-solving tasks may be greatly impacted by individual differences in behaviour, since animals with distinct behavioural types perceive and interact with their environment differently, resulting in variable responses to the same stimuli. Here, we tested whether and how differences in ranging behaviour of free-range chickens affect motor self-regulation performance during a cylinder task. For this task, subjects must refrain from trying to reach a food reward through the walls of a transparent cylinder and detour to its open sides, as a sign of inhibition. Free-range chickens exhibited an overall low performance in the motor self-regulation task (31.33 ± 13.55% of correct responses), however, high rangers showed significantly poorer performance than the low rangers (23.75 ± 9.16% versus 40 ± 12.90%, respectively). These results give further support to the impacts of individual behavioural differences on cognitive performances. This is the first demonstration to our knowledge of a relationship between exploratory tendencies and motor self-regulation for an avian species.

Relationship between ranging behavior and spatial memory of free-range chickens.

Different personalities may lead to different ways of processing environmental information; however, the relationship between personality and cognition is not fully understood as studies on diverse species present contrasting results. As there is great within-flock variability of outdoor ranging behavior in free-range broiler chickens, we tested whether and how ranging behavior impacts on individual spatial memory abilities. The experiment was conducted on one flock (n = 200) reared in the same conditions throughout the study, to simulate on-farm situations. As the ranging behavior was stable over time, we compared two distinct groups of male chickens: one that visited the range more (High rangers) and one that was more prone to staying in the poultry house (Low rangers). To test the spatial memory, individuals (n = 30) went through two main phases in an arena with 8 cups. For the familiarization phase, individuals were submitted to one trial per day, for seven days, to a situation where all eight cups were baited with mealworms. Animals had to reach a criterion of 5 cups visited out of 8 to advance to the next phase. For the spatial test, only four cups were baited and systematically placed at the same location. This last phase comprised two trials per individual per day, for nine days. During these two phases, latency to visit cups and the number of visits and revisits of all cups were recorded. Low ranger chickens took less time to attain the pre-established threshold of visiting 5 cups out of 8, over the familiarization phase. During the spatial test, the latency to visit four cups decreased between the within-day trials for low ranger chickens and increased for high ranger chickens. Moreover, in the within-day trial analysis, low ranger chickens exhibited an improvement on spatial memory and better spatial memory compared to high ranger chickens. Different speed-accuracy trade-offs may explain these differences between low and high ranger chickens and the way individuals interact and solve the task. Our study strengthens the scientific evidence relating consistent individual differences in behavior, with the ranging behavior of free-range chickens, and cognitive performance during a spatial memory task.

Behavioral evidence of heterospecific bonding between the lamb and the human caregiver and mapping of associated brain network.

While behavioral mechanisms of bonding between young mammals and humans have been explored, brain structures involved in the establishment of such processes are still unknown. The aim of the study was to identify brain regions activated by the presence of the caregiver. Since human positive interaction plays an important role in the bonding process, activation of specific brain structures by stroking was also examined. Twenty-four female lambs reared in groups of three were fed and stroked daily by a female caregiver between birth and 5-7 weeks of age. At 4 weeks, an isolation-reunion-separation test and a choice test revealed that lambs developed a strong bond with their caregiver. At 5-7 weeks of age, lambs were socially isolated for 90min. They either remained isolated or met their caregiver who stroked them, or not, at regular intervals over a 90-min period. Neuronal activation was investigated at the end of the period for maximum c-Fos expression. Reunion with the caregiver appeased similarly the lambs whether stroking was provided or not. Stroking did not activate a specific brain network compared to no stroking. In both cases, brain regions associated with olfactory, visual and tactile cue processing were activated in the presence of the caregiver, suggesting a multisensory process involved. In addition, activation of the oxytocinergic system in the hypothalamic paraventricular nucleus induced by the presence of the caregiver suggests similar neuroendocrine mechanisms involved in inter-conspecific and animal-human bonding.

Behavioral and endocrine evaluation of the stressfulness of single-pen housing compared to group-housing and social isolation conditions.

Regulation of neuroendocrine responses is often studied in animals housed indoors in individual contiguous pens. In sheep, these housing conditions are used to control the environment, facilitate biological sampling and limit social stress. However, this type of housing also prevents exploratory behaviors and could induce stereotypies, non-compliant with welfare and possibly associated with a state of stress. In this context, we investigated the impact of housing in a single-pen, with other familiar conspecifics, on emotional state by evaluating behavioral, hormonal and neuronal measures in adult ewes. We hypothesized that emotional state would be more negative in animals housed in a single-pen for one week (Pen) than in freely moving animals (Free) but less negative than in socially isolated subjects (Isol). We tested our hypothesis in ovariectomized ewes to avoid the interaction with sexual steroid variations. Our behavioral, endocrine and neuronal (Fos activation of the corticotropin-releasing hormone neurons in the paraventricular nucleus of the hypothalamus) measures confirmed that withdrawing familiar conspecifics was sufficient to induce strong stress responses in Isol ewes, but there was no indication that Pen ewes were stressed. However, the latter showed less mastication activity than Free ewes, probably due to limited accessibility to straw. The highest plasma prolactin levels were observed in Isol and Free animals, which might result from stress and physical activity, respectively. In Free ewes, plasma dopamine was low, consistent with its inhibitory control of prolactin. However, Isol animals had both high levels of prolactin and dopamine, suggesting a dysregulated balance in socially stressed ewes. As in other species, we suggest that the regulation of prolactin by dopamine varies with stress and/or social context. Overall, this study shows that the impact of housing conditions on different neuroendocrine systems should be considered more in the future.

Rapid effects of melatonin on hormonal and behavioral stressful responses in ewes.

Sheep are gregarious mammals with complex social interactions. As such, they are very sensitive to social isolation and constitute a relevant animal model to study specifically the biological consequences of social stress. We examined previously the behavioral and endocrine responses in ewes isolated socially in the familiar conspecific withdrawal model (FCW) and showed that stressful responses increased and maintenance behaviors decreased, confirming that social isolation is a strong stressor in sheep. Melatonin synchronizes seasonal and circadian rhythms; and several studies reported its implication in cognitive processes as emotion. Here we investigated its role in the modulation of social stressful responses. Firstly, we studied ewes in the FCW model during the day (characterized by low melatonin levels) and the night (characterized by high melatonin levels). We found lower stressful responses (significant lower levels of cortisol plasma, number of foot pawings, of circling attempts) during the night as compared to the day. To investigate whether these effects were due to melatonin or to darkness, we submitted ewes to FCW during the night with lights on, a condition that suppresses melatonin secretion. Ewes infused with melatonin under these conditions showed decreased stressful responses (significant lower levels cortisol plasma, number of vocalizations, time spent with the head out of the cage) as compared to ewes infused with saline. These findings demonstrate that melatonin diminishes the endocrine and behavioral impact of social isolation in ewes and support the idea that melatonin has a calming effect in socially stressful situations.

Multiple exposures to familiar conspecific withdrawal is a novel robust stress paradigm in ewes.

Paradigms used so far to study the effects of social isolation in sheep confound the effects of social isolation with those of other stressors (e.g. new environment) and showed contradictory effects after multiple social isolations. We propose here to characterize and examine the repeatable effects of social isolation induced by the familiar conspecific withdrawal (FCW). This latter test consists of socially isolating the ewe by the removal of group mates from the room test for 3 h. Behavioral and endocrine responses of adult ovariectomized-estradiol implanted ewes were compared 90 min before and 90 min after FCW, which was applied three times every fourteen days. We observed that each FCW induced significant increases in plasma cortisol level, in the number of vocalizations, foot pawing, circling attempts and a significant decrease in time spent lying down. An increase in plasma cortisol levels and decrease in duration of maintenance behaviors were significantly lower after the third FCW than after the first one. These differences could be explained by higher plasma cortisol levels and lower duration of maintenance behaviors before the third FCW than before the first FCW suggesting an anticipation of the social isolation period. These data indicate that social isolation is sufficient to induce distress with stable stressful responses after multiple exposures to familiar conspecific withdrawal.

A place to hide in the home-cage decreases yolk androgen levels and offspring emotional reactivity in Japanese quail.

An animal's emotional responses are the result of its cognitive appraisal of a situation. This appraisal is notably influenced by the possibility of an individual to exert control over an aversive event. Although the fact that environment controllability decreases emotional responses in animals is well established, far less is known about its potential trans-generational effects. As the levels of avian yolk hormones can vary according to the mother's environment, we hypothesized that housing environment of mothers would modulate the quality of her eggs and in turn her offspring's behaviour. Two groups of female Japanese quail were constituted: a group that had access to a place to hide in their home-cage (Hd, n = 20) and a group that had nowhere to hide (NoHd, n = 20) when stressed. Both groups were submitted to daily human disturbances for a twenty-day-period. Hd females produced eggs with both less testosterone and androstenedione than did NoHd females. The emotional and social reactivity of Hd females' offspring were lower and their growth was slower than those of NoHd females' offspring. Our results show that a minor difference in housing environment had substantial effects on eggs and offspring. The presence of a shelter probably helped quail to cope with daily human disturbances, producing less reactive offspring. This transgenerational effect caused by an opportunity to hide could lead to applications in care of laboratory animals, conservation biology and animal welfare.