Ruth C. Newberry

Hen welfare in different housing systems

Egg production systems have become subject to heightened levels of scrutiny. Multiple factors such as disease, skeletal and foot health, pest and parasite load, behavior, stress, affective states, nutrition, and genetics influence the level of welfare hens experience. Although the need to evaluate the influence of these factors on welfare is recognized, research is still in the early stages. We compared conventional cages, furnished cages, noncage systems, and outdoor systems. Specific attributes of each system are shown to affect welfare, and systems that have similar attributes are affected similarly. For instance, environments in which hens are exposed to litter and soil, such as noncage and outdoor systems, provide a greater opportunity for disease and parasites. The more complex the environment, the more difficult it is to clean, and the larger the group size, the more easily disease and parasites are able to spread. Environments such as conventional cages, which limit movement, can lead to osteoporosis, but environments that have increased complexity, such as noncage systems, expose hens to an increased incidence of bone fractures. More space allows for hens to perform a greater repertoire of behaviors, although some deleterious behaviors such as cannibalism and piling, which results in smothering, can occur in large groups. Less is understood about the stress that each system imposes on the hen, but it appears that each system has its unique challenges. Selective breeding for desired traits such as improved bone strength and decreased feather pecking and cannibalism may help to improve welfare. It appears that no single housing system is ideal from a hen welfare perspective. Although environmental complexity increases behavioral opportunities, it also introduces difficulties in terms of disease and pest control. In addition, environmental complexity can create opportunities for the hens to express behaviors that may be detrimental to their welfare. As a result, any attempt to evaluate the sustainability of a switch to an alternative housing system requires careful consideration of the merits and shortcomings of each housing system.

Use of Pen Space by Broiler Chickens: Effects of Age and Pen Size

An experiment was conducted to investigate the effects of age and pen size on the use of pen space by male broiler chickens. The locations of 18 marked chickens in a large pen (407 m2 with 3040 birds) and 10 in each of two small pens (203.5 m2 with 1520 birds) were recorded at hourly intervals, 8 times per day, on 5 consecutive days per week, from 4 to 9 weeks of age. Results indicated that the use of pen space was non-random (P<0.05). Chickens stayed nearer to pen walls than expected by chance in both pen sizes and during all weeks (P<0.01). In addition, chickens in the large pen, although not the small pens, stayed closer to their brooding site than expected (P<0.01). The area of space occupied per day and per week declined with increasing age (P<0.01) and was not affected by pen size. However total space used from 4 to 9 weeks was greater in the large than the small pens (P<0.05). Distance moved per hour declined with age in both pen sizes (P<0.01). Although movements were non-random, the chickens did not restrict their movements to small areas in which they could become acquainted with their neighbours over the period from 4 to 9 weeks of age. Possible implications for broiler welfare of the lack of a well-delineated home site and continual mingling with strangers are discussed.

Group size and perching behaviour in young domestic fowl.

To test the hypothesis that young domestic fowl perform less perch-related antipredator behaviour with increasing group size, White Leghorn pullets were reared in four replicate groups of 15, 30, 60 and 120 at a constant density of 5 birds/m(2). Each pen contained perches 20, 40 and 60cm above the ground. Perch space per bird per perch level was the same for all groups. It was predicted that, with increasing group size, domestic fowl would (1) spend less time on perches (i.e. more time down on the floor); (2) be less vigilant while perching; (3) spend relatively more time preening down on the floor. As predicted, the proportion of 3- to 18-week-old birds roosting on perches during scans throughout the photoperiod decreased with increasing group size, from 41+/-1.7% in groups of 15 birds to 33+/-1.6% in groups of 120 birds. This effect was due to reduced use of the lower perches; use of the highest perches was high at all group sizes. The proportion of birds vigilant on the highest perches of those present on that perch level decreased with increasing group size. The proportion of birds engaged in the vulnerable activity of preening down on the floor increased with group size. The frequency of transitions between floor and perches was not affected by group size but birds received more disturbances from other birds when on the top perch level in the larger groups. Thus, the decline in vigilance on the top perch level with increasing group size was not due to reduced disturbance from other birds. In conclusion, despite domestication and protection from non-human predators, changes in the use of perches by young domestic fowl with increasing group size were consistent with the antipredator hypothesis.

Dynamics of aggression in the domestic fowl

Abstract We conducted three experiments designed to investigate the effect of group size (GS) on the frequencies of different types of aggressive acts performed by 11–21-week-old White Leghorn pullets. In these experiments, we systematically controlled for bird density, pen size, and previous social experience in groups of different sizes. Aggression was measured in the context of competition for a limited supply of highly attractive food provided in two patches (central and peripheral) in addition to the regular (ad libitum) food supply. The birds were observed in their original groups of 15, 30, 60 and 120 birds (3–4 replicate groups per GS), reared together since hatch, or in temporary sub-groups of the original groups. In the first experiment (space per bird constant, pen size and GS history varying), the number of aggressive pecks delivered per food patch declined as GS increased from 15 to 120 birds. In the second experiment, utilising birds from the groups of 120 only (space per bird varying, pen size and GS history constant), the number of aggressive pecks delivered per patch increased as temporary GS increased from 15 to 60 birds. In the third experiment (space per bird and pen size constant, GS history varying), the number of aggressive pecks delivered per patch was constant among groups of 15 birds obtained from the groups of 15, 30, 60 and 120 birds. In all experiments, the central food patch was exploited sooner than the peripheral one. The actual number of birds at a food patch at a given time was more important in determining the frequency of aggression at the food patch than the number of birds present in an enclosure or previous GS experience. When a high number of individuals was present at a food patch, aggression at that patch was relatively infrequent. The results support the hypothesis that aggression in the domestic fowl is a dynamic process, with decisions about aggressive behaviour being made facultatively according to the relative costs and benefits of different behavioural strategies at a given time and place rather than being fixed obligatorily at a constant level according to the number of birds present in an enclosure and their ability to form dominance relationships.

Social relationships of piglets in a semi-natural environment

Abstract The social relationships of domestic piglets ( Sus scrofa ) kept with adult and juvenile pigs in a large outsid enclosure were examined. Focal and scan sampling techniques were used to collect data on five measures of social behaviour: resting, social facilitation, nearest neighbours, butting and sniffing. Cluster analysis indicated that, between birth and 13 weeks of age, piglets had stronger social relationships with littermates than with non-littermates, their dam, other adults or juveniles but social preferences were not found between particular pairs of littermates. Litters were born in separate farrowing nests but nonlittermates came into contact within 15 days of birth. Fostering occurred when two piglets switched dams spontaneously, and these piglets subsequently exhibited stronger relationships with their foster than with their natural littermates. Results are discussed with reference to intensive housing systems and evolutionary pressures.

Exploratory behaviour of young domestic fowl

Abstract Under the hypothesis that young domestic fowl, Gallus gallus , are motivated to seek opportunities to explore novel stimuli, it was predicted that broiler chickens would show greater motivation to enter peripheral space if it contained (a) novel objects (changed daily) than if it was (b) empty or contained (c) essential resources (food, water, heat) or (d) supplementary resources (peat moss, straw bale, elevated platform). Sixteen pens, each containing 100 chickens, were set up with a home area containing essential resources and an adjacent peripheral area of the same size to which the chickens were allowed access for 3 h daily by opening a gate. There were four replicate pens on each of four treatments varying in the resources (a–d) provided in the peripheral area. During week 6, continuous video recordings showed that more chickens on the novel objects treatment ran into the peripheral area during the first 5 min after the gates were opened than did chickens on the other three treatments ( P P >0.05). The results support the hypothesis that the chickens were motivated to seek opportunities to explore novel stimuli.

Recent social experience, body weight and initial patterns of attack predict the social status attained by unfamiliar hens in a new group

To enhance understanding of processes determining social dominance, we quantified the contributions of existing individual characteristics and experience, and information obtained during initial encounters with new group members, on social status attained by hens ( Gallus gallus domesticus ) in a new group. We hypothesised that previous social experience (either with strangers or flock mates), body weight and comb size would be good predictors of a hen′s aggressive behaviour and subsequent social status. Using structural equation modelling, we identified best-fit models to predict the outcome of combining unfamiliar individuals varying in these characteristics. In new triads of 150 red rock × light Sussex hens, hens with a relatively large comb and high body weight were more likely to have won a recent fight and performed more double attacks in their new group. Hens with recent experience of winning were more likely to attain the alpha position in the new group. In a second trial on new tetrads of 32 white leghorn hens, hens with a higher body weight performed more double attacks, leading to a higher rank in their new group. Hens that had recently been high ranking in their former social group also tended to perform more double attacks. Comb size and plumage condition were not good predictors of attack behaviour or rank in this trial. In both trials, a hen′s body weight had predictive value in determining her attack behaviour and subsequent social status when introduced to a small number of strangers. We suggest that the timing and quality of social experience obtained prior to regrouping, the relative difference in comb size between opponents, and the absolute size and carriage of the comb (upright or floppy), influenced the efficacy of previous social experience and comb size as predictors of behaviour and rank in a new group.

Octodon degus. A useful animal model for social-affective neuroscience research: basic description of separation distress, social attachments and play.

A challenge for social-affective neuroscience programs is to identify simple and yet valid animal models for studying the expression of basic social emotions and their role during different developmental windows, from infancy to adulthood. For example, although laboratory rats are useful for studying juvenile social interactions, they are not ideal for studying infant attachment bonds. Here, we evaluate current understanding of the social behavior of Octodon degus, a diurnal precocial rodent, to elucidate the value of this species as a model for social-affective neuroscience research. After a synopsis of species-specific characteristics and brain susceptibility to changes of social environment, our behavioral findings on degu social proclivities are summarized. We then discuss why this pre-clinical model provides a valuable addition to the commonly available animal models for the study of human psychopathology.

Cannibalistic behaviour spread by social learning

Abstract We hypothesized that social learning is involved in the spread of cannibalism in domestic fowl Gallus gallus domesticus . To investigate this hypothesis without harming birds, we used an inanimate chicken model as our cannibalism stimulus. We randomly assigned flocks of 12 White Leghorn pullets to one of two treatments: (1) flocks with two trained demonstrators ( N =9) and (2) control flocks ( N =8). Demonstrators were trained to pierce a membrane covering a dish of chicken blood and consume the blood. To assess the effect of access to the cannibalism stimulus during demonstrations, we randomly assigned observer pairs to one of two observer treatments: (1) observe stimulus through a wire mesh partition and (2) observe stimulus within the same enclosure. We conducted five 10-min demonstration sessions, each followed by a 10-min test of each observer pair in the absence of demonstrators, over a period of 15 days when the birds were 41–55 days of age, and two further tests at 63–64 and 91–92 days of age. Pairs that observed demonstrators piercing a membrane and consuming blood were more likely to perform this task when tested than control pairs. Learning of the task was enhanced by direct access to the cannibalism stimulus rather than observing it through a wire mesh partition. Blood consumption during tests was increased by direct access to the cannibalism stimulus during demonstration sessions. The birds made bigger holes in the membrane when tested after observing trained demonstrators and after having direct access to the stimulus. Our results provide the first experimental evidence that social learning can contribute to the spread of cannibalistic behaviour in domestic fowl. We suggest that stimulus enhancement and observational conditioning were the social-learning mechanisms involved. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved .

Does pecking at inanimate stimuli predict cannibalistic behaviour in domestic fowl

We assessed the pecking behaviour of caged White Leghorn hens towards feather-shaped stimuli varying in colour (red or blue), material (paper or feather) and movement (stationary or movable) attached to a board placed in the feed trough. Each of the eight stimulus combinations was presented to two replicate groups of 5 young hens for 15 min at 45 and 57 days of age. We predicted that the birds would be especially attracted to red movable feathers simulating a live bird with bloodstained feathers. Severe (forceful) pecks were directed more frequently at feather than paper stimuli (P<0.05) and at movable than stationary stimuli (P<0.01) but there was no differential response to red and blue stimuli. We reassessed responses to the stimuli by a subset of the original birds, now in 16 groups of four hens, at 696 and 710 days of age. We found no significant effects of colour, material or movement on the latency to peck the stimuli, or the frequency of gentle and severe pecks at the stimuli, indicating that responses to the stimulus characteristics were not consistent between young and old hens. There was a positive correlation between the frequency of severe feather pecking at flock mates and the frequency of cannibalistic behaviour (P<0.01), consistent with reports that bleeding resulting from feather pecking can lead to cannibalism. We found no significant correlation between the frequency of pecking at the inanimate stimuli and the frequencies of pecking at the flesh and feathers of flock mates. This analysis does not take into account possible behavioural differences between primary cannibals that drew blood and secondary cannibals that joined a cannibalistic attack once blood had been drawn. We conclude that the frequency of pecking at inanimate stimuli was not a good predictor of future cannibalistic behaviour by the hens in this study. However, a tendency for future cannibals and severe feather peckers to have longer latencies to peck the inanimate stimuli warrants further investigation. It will be possible to use responses to specific types of inanimate stimuli to predict cannibalistic tendencies only if future cannibals are found to have stable responses to those stimuli over time.