Influence of Different Light Spectrums on Behaviour and Welfare in Laying Hens.

Artificial commercial lighting used in animal production facilities can have negative influences on visual abilities, behaviour and welfare of domestic fowl. This study examined the effects of natural-derived light spectrums on behaviour, production and welfare of laying hens reared from hatching into adulthood. Comparisons were made of frequency of a range of behaviours associated with activity, aggression and comfort in birds kept in control light (commercial standard), daylight (full spectrum, including ultraviolet (UV) wavelengths and forest light (forest understorey, including UV). In addition, bird preferences for different lights, feather damage and egg production were monitored. The results showed that the behavioural repertoire of birds changed with age, while the effects of light treatment were subtle. Some evidence was found that birds preferred either daylight or forest light to control light, suggesting that inclusion of UV contributed to the preference. Daylight and forest light were associated with more active behaviours, and daylight with better plumage and later start of lay. Thus natural-like light may have beneficial effects on domestic fowl, but the differences between broad-spectrum light sources are rather small.

Environmental complexity: A buffer against stress in the domestic chick.

Birds kept in commercial production systems can be exposed to multiple stressors from early life and this alters the development of different morphological, immunological and behavioural indicators. We explore the hypothesis that provision of a complex environment during early life, better prepares birds to cope with stressful events as well as buffers them against future unpredictable stressful episodes. In this study, 96 one day old pullets were randomly distributed in eight pens (12 birds/pen). Half of the chicks (N = 48) were assigned to a Complex Environment (CENV: with perches, a dark brooder etc.) the others to a Simple Environment (SENV: without enrichment features). Half of the birds from each of these treatments were assigned to a No Stress (NSTR, 33°C) or to an acute Cold Stress (CSTR, 18-20°C) treatment during six hours on their second day of life. At four weeks of age, chicks with these four different backgrounds were exposed to an Intermittent Stressful Challenges Protocol (ISCP). In an immunological test indicative of pro-inflammatory status Phytohemagglutinin-P (PHA-P), the response of CSTR birds was ameliorated by rearing chicks in a CENV as they had a similar response to NSTR chicks and a significantly better pro-inflammatory response than those CSTR birds reared in a SENV (five days after the CSTR treatment was applied). A similar better response when coping with new challenges (the ISCP) was observed in birds reared in a CENV compared to those from a SENV. Birds reared in the CENV had a lower heterophil/lymphocyte ratio after the ISCP than birds reared in SENV, independently of whether or not they had been exposed to CSTR early in life. No effects of stress on general behaviour were detected, however, the provision of a CENV increased resting behaviour, which may have favoured stress recover. Additionally, we found that exposure to cold stress at an early age might have rendered birds more vulnerable to future stressful events. CSTR birds had lower humoral immune responses (sheep red blood cells induced antibodies) after the ISCP and started using elevated structures in the CENV later compared to their NSTR conspecifics. Our study reflects the importance of the early provision of a CENV in commercial conditions to reduce negative stress-related effects. Within the context of the theory of adaptive plasticity, our results suggest that the early experience of the birds had long lasting effects on the modulation of their phenotypes.

Ability of Laying Hens to Distinguish Between Companions According to Their Success in Gaining Access to Food.

Laying hens (Gallus gallus) are social birds with cognitive abilities related to having a functional interaction with their peers. Gaining knowledge about for example new food sources from other individuals can be a valuable complement to individual learning and probably even more so if one copies the behavior of successful individuals. In this study the aim was to investigate if a bird would identify another bird as being successful at gaining access to food. A social cognition feeding test was developed where birds could move freely together between several scattered food sources. Two different methods were used for training. In method 1, the observer hens were exposed to a skilled demonstrator hen that gained access to the food sources and an unskilled demonstrator hen (that gained no access to food) at the same time when trained together in a trio. In method 2, the observer was trained in two different pair constellations, with a skilled and unskilled demonstrator, respectively. In the test situation for both methods birds were paired, one observer was tested once with the skilled demonstrator and once with the unskilled demonstrator. Observations of how much the observer birds followed the two different demonstrators to the food sources, although no food was available during testing, were carried out. Observers trained in trios (method 1) did not show any difference in following behavior between the skilled and unskilled demonstrator, but observers that had been trained in pairs (method 2) showed more following behavior toward the skilled demonstrators than the unskilled demonstrator (P = 0.005). Thus the results indicate that laying hens are able to use another bird as a cue of whether they will get access to food.

Methods for Investigating the Motivation of Mice to Explore and Access Food Rewards.

The emotional state of domestic animals is an essential component of the assessment of their welfare. In addition, sensitivity to various rewards can be a valuable indicator when investigating these states. We aimed to design an exploration test and a contrast test that did not evoke fear and anxiety in C57BL/6N mice but that instead were perceived as positive experiences and that might be used to assess sensitivity to various rewards. The exploratory arena had a larger central area and 8 smaller sections containing various objects. Motivation (measured as latency to enter the arena under conditions of increasing weight of the entrance door), anticipation (measured as latency to enter the arena under conditions of increasing delay in opening the entrance door), and the numbers of visits to the different sections were evaluated during a 5-min session in the arena. In the contrast test, after traversing a runway, half of the mice received a tasty reward (hazelnut cream), whereas the others received a neutral reward (food pellet) at the far end. Latency to reach the reward was recorded. After baseline training, rewards were swapped for half of the mice from each category for 3 d, to establish a negative and positive contrast. Mice were both motivated and showed anticipation to enter the exploration arena; after entering, they were active and visited many sections. In the contrast test, latency during the baseline period was longer for mice given the neutral reward compared with the tasty reward. Compared with baseline, latency during the postshift phase decreased for the positive-contrast group (neutral-tasty reward pattern) but did not differ for the negative-contrast group (tasty-neutral reward pattern). Overall, both tests seemed to be positive experiences for the mice and showed potential for use to investigate reward sensitivity.

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.

Light exposure during incubation and social and vigilance behaviour of domestic chicks.

Light exposure of chick eggs during a sensitive period at the end of the incubation period leads to the development of lateralised visual behaviour, and here we show that social behaviour is also influenced by this exposure. Groups of eight chicks of three types-(1) all incubated in the dark (Da), (2) all exposed to light (Li), (3) half Da and half Li (Mixed)-were tested on a range of tasks involving social competition and vigilance for a simulated predator. We confirmed a previous finding that lowest-ranking chicks in Li groups gained less access to a food bowl when they had to compete with group members than did the lowest-ranking chicks in the Da groups, and we extended this result to show that the Mixed groups performed like the Li groups. We also showed that before presentation of a novel stimulus resembling a predator, fewer of the chicks in the Da groups than in the Li and Mixed groups looked up, but during presentation of the predator more Da than Li chicks looked up. Hence, light exposure before hatching affects post-hatching social and vigilance behaviour.

Transmission of stress-induced learning impairment and associated brain gene expression from parents to offspring in chickens.

BACKGROUND: Stress influences many aspects of animal behaviour and is a major factor driving populations to adapt to changing living conditions, such as during domestication. Stress can affect offspring through non-genetic mechanisms, but recent research indicates that inherited epigenetic modifications of the genome could possibly also be involved. METHODOLOGY/PRINCIPAL FINDINGS: Red junglefowl (RJF, ancestors of modern chickens) and domesticated White Leghorn (WL) chickens were raised in a stressful environment (unpredictable light-dark rhythm) and control animals in similar pens, but on a 12/12 h light-dark rhythm. WL in both treatments had poorer spatial learning ability than RJF, and in both populations, stress caused a reduced ability to solve a spatial learning task. Offspring of stressed WL, but not RJF, raised without parental contact, had a reduced spatial learning ability compared to offspring of non-stressed animals in a similar test as that used for their parents. Offspring of stressed WL were also more competitive and grew faster than offspring of non-stressed parents. Using a whole-genome cDNA microarray, we found that in WL, the same changes in hypothalamic gene expression profile caused by stress in the parents were also found in the offspring. In offspring of stressed WL, at least 31 genes were up- or down-regulated in the hypothalamus and pituitary compared to offspring of non-stressed parents. CONCLUSIONS/SIGNIFICANCE: Our results suggest that, in WL the gene expression response to stress, as well as some behavioural stress responses, were transmitted across generations. The ability to transmit epigenetic information and behaviour modifications between generations may therefore have been favoured by domestication. The mechanisms involved remain to be investigated; epigenetic modifications could either have been inherited or acquired de novo in the specific egg environment. In both cases, this would offer a novel explanation to rapid evolutionary adaptation of a population.