Rafael Freire

Behaviour and welfare of individual laying hens in a non-cage system

1. A leg band containing a transponder was fitted to 80 birds in a perchery containing 1000 birds. 2. The transponder emitted a unique identification number when a bird walked on one of 8 flat antennae on the floor. The recording apparatus was used to measure the amount of time that each of the tagged birds spent on the slatted and littered areas in a 6-week period. 3. Some birds spent long periods of time on the slats, possibly as a means of avoiding repeated attacks. Duration on the slats was greatest in birds with the worst (as opposed to better) feather scores of the head, back and tail regions. 4. Birds that spent long periods on the slats were lighter than other birds at both 39 weeks of age and 72 weeks of age and had greater back, head and tail feather damage, consistent with these birds being victims of pecking. 5. Tagged birds received a social avoidance test outside the perchery at 39 weeks of age, which suggested that birds retreated to the slats in response to pecks rather than just to close proximity to other birds. 6. The failure to find that duration on the slats was related to anatomical indicators of stress (liver, spleen and bursa of Fabricius) suggests that retreating to the slats following pecking attenuates physiological stress responses. 7. We conclude that the provision of areas where birds in a large group can avoid pecking may improve the welfare of a minority of victimised birds.

Chickens orient using a magnetic compass

Document S1. Supplemental Experimental Procedures.xDownload (.04 MB ) Document S1. Supplemental Experimental Procedures.

Pre- and post-hatching effects of corticosterone treatment on behavior of the domestic chick.

We investigated the effect of 60 ìg of corticosterone administered to domestic chicks either before or after hatching on the behavioral response to isolation in a novel arena and performance in a task involving the simultaneous identification of food and detection of a predator (overhead silhouette of a hawk moving overhead). Following release into a novel arena, chicks treated with corticosterone at 18 days of incubation emitted more distress vocalizations. In contrast, no difference in the number of vocalizations was found between chicks treated with corticosterone at day 1 post-hatching and controls. Behavior in the home cages was generally similar across treatments, though chicks treated with corticosterone at 18 days of incubation slept more than control chicks. While searching for grain against a background of pebbles, chicks treated with corticosterone at embryonic day 18, but not chicks treated on day 1 post-hatching, took longer to detect the overhead image of a predator than did controls. Corticosterone treatment at both ages increased the rate of pecking at grains and pebbles. Our findings support work on other birds indicating that corticosterone treatment during incubation influences stress reactivity. The impairment in predator detection in chicks treated with corticosterone on day 18 of incubation appears to be caused by the known effects of corticosterone treatment at this age in preventing the development of lateralization of the thalamofugal visual projections. This further supports the hypothesis that brain lateralization provides an advantage in performing more than one task simultaneously.

Lateralized response of chicks to magnetic cues

Previous research has shown that the ability to orient with the use of directional cues from the geomagnetic field is lateralized in three avian species: orientation is possible when the birds are restricted to use of their right eye, but not when they have to use their left eye. This has been interpreted as possible lateralization of the perception mechanisms for magnetic cues in favour of the right eye. Recent discovery of magnetic compass orientation in domestic chicks, a species in which lateralization has been well studied, has made available a model system in which to explore these lateralized processes more fully. Hence we tested chicks monocularly in the same test conditions as used previously to demonstrate the chicks use of a magnetic compass. In a magnetic field with North shifted by 90 degrees , chicks using their right eye oriented according to magnetic cues, whereas chicks using the left eye did not, but continued to prefer the original direction. Analysis of the times taken to respond indicated longer latencies in the chicks using their left eye, suggesting a possible conflict between cues. The different behaviour of the chicks using their left eye might not be a matter of a right eye-left hemisphere specialization for detecting magnetic directions, but of hemispheric specialization for attending to specific types of cues.

Development of spatial memory in occlusion-experienced domestic chicks

Abstract At around day 11 of life, domestic chicks show a tendency to move out of sight of their mother before returning and regaining social and visual contact. We conducted a series of experiments to investigate the role of this voluntary ‘out-of-sight’ behaviour on the development of spatial memory in young chicks. We compared the behaviour of chicks that were reared in environments that provided opportunities to move out of sight of an imprinting stimulus (occlusion-experienced chicks) with the behaviour of chicks that were given minimal occlusion experience (controls). As in natural conditions, out-of-sight behaviour peaked on day 11. When chicks were released into larger pens at 14 days of age, occlusion-experienced chicks walked more than control chicks, but otherwise showed similar degrees of dispersal. Occlusion-experienced chicks tended to show better (although not significant, P =0.09) retrieval of a visually displaced imprinting stimulus than control chicks. Time spent out of sight in the rearing pens was negatively related to the number of orientation errors in a detour test. Occlusion-experienced chicks also tended to make fewer orientation errors in the first trial ( P =0.07) and in subsequent trials ( P =0.05). In contrast, experimentally manipulating the amount of time that chicks were out of sight of an imprinting stimulus (by confining the chicks) had no effect on their performance in displacement or detour tests. The results presented here suggest that active experience of occlusion around day 11 improved egocentric orientation towards an out-of-sight goal, supporting the hypothesis that enrichment-induced behavioural changes are dependent on the interaction with objects.

Effects of different forms of exercise on post inhibitory rebound and unwanted behaviour in stabled horses

REASONS FOR PERFORMING STUDY It is unknown if different locomotor activities are equally effective at meeting the stabled horses need for exercise and if they attenuate unwanted behaviour. HYPOTHESIS Alternative forms of exercise influence the intensity of locomotor activities during a period of turn-out (the so-called rebound effect) and the occurrence of unwanted or undesirable activities during standard handling situations. METHOD Twenty-four horses kept in stables were randomly assigned to one of 4 exercise regimes (walker, treadmill, turn-out and riding) for 4 consecutive days. Because these forms of exercise provide additional environmental stimulation, beyond that provided by exercise, each horse served as its own control in 4 corresponding (no exercise) control treatments presented in a balanced order. Unwanted behaviour was tested by taking horses to weighing scales and loading and unloading them onto a 4-horse float by an experienced handler and the rebound effect was tested by releasing them into a large arena for a period of 15 min at the end of the exercise and control treatments. RESULTS Locomotor activities made up a large part of behaviour in the large arena following control treatments and all exercise regimes were sufficient to reduce the intensity of walking (P < 0.05), trotting (P < 0.01) and cantering (P < 0.001) on release into a large arena. Exercise regime reduced the number of bucks (P < 0.01) and rolling (P < 0.05) during rebound tests suggesting that turn-out was having a stronger effect than the other 3 exercise regimes. Exercise regimes significantly reduced the amount of unwanted behaviour and the number of commands given by the handler during weighing (P < 0.05) but had no effect on these behaviours during loading onto a float. CONCLUSION Providing stabled horses with one hour/day of exercise on a walker, treadmill, turn-out or by being ridden are all effective at allowing expression of locomotor activities in stabled horses. POTENTIAL RELEVANCE Providing stabled horses with regular exercise is likely to provide positive effects on horse welfare, training ability and handler safety.

Experience‐dependent changes in the hippocampus of domestic chicks: a model for spatial memory

In the domestic chicken, providing visual barriers for a brief period early in life has been found to improve spatial memory [R. Freire et al. (2004)Animal Behaviour, 67, 141–150]. In the present study we compared the structure of neurons in the hippocampus and neostriatum in chicks reared with or without visual barriers. From 8 to 16 days of age, chicks were reared in pens either with two wooden screens (Treatment E) or with no screens (Treatment C). At 16 days of age, chicks were anaesthetized, perfused intracardially and brain samples collected and stained using a Golgi–Cox technique. Morphometric analysis revealed that the multipolar projection neurons of Treatment E chicks had longer dendrites (anova, F1,14 = 7.4, P < 0.05) and had more spines per 20 µm of dendrite (SLD; anova, F1,14 = 10.6, P < 0.01) than those of Treatment C chicks. By contrast, no evidence was found that rearing treatment differentially influences dendrite length or SLD in the neostriatum, suggesting that the above environment‐induced changes may be specific to the hippocampus. Multipolar projection neuron dendrites of the right hemisphere were longer (anova, F1,14 = 36.4, P < 0.0001) and had more spines (anova, F1,14 = 8.8, P < 0.05) than dendrites of the left hemisphere, supporting previous findings that the right hemisphere of chickens is predominantly involved in spatial processing. We conclude that the chicken provides a useful model for the study of developmental plasticity in brain and behaviour, partly because the possibility of rearing chicks in isolation and imprinting them on an artificial object provides a means of accurately manipulating early experience.

Factors affecting ranging behaviour in commercial free-range hens

Many studies have assessed use of the outdoor ‘range’ area on free-range laying farms, and have revealed that percentage range use at any one time rarely exceeds 50% of the flock, and is sometimes below 10%. What constitutes a ‘good’ range use is difficult to determine without better knowledge of ranging bout lengths under ideal conditions. Well documented factors that affect percentage range use include prevailing weather, flock size and shelter on the range. Other factors such as pophole design, internal and external stocking density and system design appear to play a role although their effects are not as clear and more research would be valuable to truly understand their relevance. Factors affecting bird distribution on the range are also reviewed.

Different responses in two strains of chickens (Gallus gallus) in a magnetic orientation test

Previous studies demonstrated that layer strain domestic chicks bred for egg production can orient using directional cues from the magnetic field; here we report that chicks from a broiler strain bred for meat production do not use magnetic cues for orientation. We imprinted both strains of chicken on a red ball and subsequently trained them in a featureless testing arena. Between rewarded trials in the geomagnetic field, we inserted unrewarded tests under the following conditions: (1) in the geomagnetic field, (2) in a magnetic field with North shifted by 90° and (3) in a magnetic field with the inclination inverted. The layer chicks made a correct axial response in 75–80% of the tests, shifting their choices following a rotation of magnetic North. Chicks of the broiler strain, in contrast, performed at chance level with between 47 and 60% of choices on the correct axis. This difference between the strains does not appear to be due to substantial strain differences in motivation to perform the task. It therefore appears possible that the selection of the broiler strain has led to the elimination of the specific ability to respond to magnetic cues in the test situation.

Experience-induced modulation of the use of spatial information in the domestic chick

We examined whether experience of opaque or transparent screens modulates the use of spatial cues by domestic chicks. From 10–12 days of age, chicks could lose sight of an imprinting stimulus or their cagemate in cages with opaque screens, but were largely unable to do so in cages with transparent screens. Chicks were then trained to find the imprinting stimulus behind one of two screens. Unrewarded probe tests were presented to chicks with the apparatus rotated by 180° so that proximal (intra-apparatus) and distal (extra-apparatus) cues indicated opposite sides of the apparatus. In tests with two distinctly different screens, chicks using the left eye (LES) chose the distal side more than the proximal side, whereas chicks using the right eye (RES) chose the proximal side more than the distal side. When using both eyes (BIN) in tests with different screens, chicks reared in cages with opaque screens were quicker in making a choice, and tended to choose the screen on the distal side more often than chicks reared in cages with transparent screens. Chicks reared in cages with opaque screens failed to make a choice less often than chicks reared in cages with transparent screens in BIN tests with different screens and in monocular tests with identical screens. The results suggest that chicks using the LES are less easily disrupted by conflicting spatial cues than chicks using the RES, and that experience of visual barriers from 10–12 days of age improves the chicks ability to attend to distal cues.