Christine J Nicol

Factors influencing the development of stereotypic and redirected behaviours in young horses: findings of a four year prospective epidemiological study

Stereotypies are invariant and repetitive behaviour patterns that seemingly have no function, which tend to develop in captive animals faced with insoluble problems and may be indicative of reduced welfare. A 4 year prospective study of the factors influencing the development of stereotypic and redirected behaviours (abnormal behaviour) in a population of 225 young Thoroughbred and part-Thoroughbred horses was conducted between 1995 and 1999. Abnormal behaviour affected 34.7% of the population. Multivariable analysis showed that foals of low- or middle-ranking mares were less likely to develop abnormal behaviour than foals of dominant mares (rate ratio (RR) 0.23, P<0.01; RR 0.48, P<0.01, respectively). Weaning by confinement in a stable or barn was associated with an increased rate of development of abnormal behaviour, compared with paddock-weaning (RR 2.19, P<0.05), and housing in barns, rather than at grass after weaning, was associated with a further increase (RR 2.54, P<0.01). Specific stereotypic and redirected behaviours were then considered as separate outcomes. Crib-biting was initiated by 10.5% of horses at median age 20 weeks, weaving by 4.6% of horses at median age 60 weeks, box-walking by 2.3% of horses at median age 64 weeks and wood-chewing by 30.3% of horses at median age 30 weeks. Wood-chewing developed at a lower rate in horses born to subordinate or mid-ranking mares than in horses born to dominant mares (RR 0.29, P<0.01; RR 0.41, P<0.01, respectively), and at a higher rate in horses kept in barns or stables rather than at grass after weaning (RR 4.49, P<0.001; RR 1A6, P<0.001, respectively). Feeding concentrates after weaning was associated with a 4-fold increase in the rate of development of crib-biting (RR 4.12, P = 0.02). The results of this study support the idea that simple changes in feeding, housing and weaning practices could substantially lower the incidence of abnormal behaviour in young horses.

Behavioural responses of laying hens following a period of spatial restriction

Six laying hens were housed singly in small cages (area 847 cm2) and six were housed singly in large cages (2310 cm2) for a period of 4 weeks. Many significant differences were found between the behaviour of the birds in the two groups. In addition, the frequency of performance of some activities, e.g. wing stretching and preening, over the 4 weeks declined in both groups, although these were most pronounced for the hens in small cages. After this period in the home cages the birds were observed simultaneously, as matched pairs, in a pair of large test cages (2310 cm2). Wing stretching, feather raising, tail wagging, leg stretching and wing flapping performed at a low frequency in the small home cages, were performed at a high frequency ‘rebound’ rate in the test cages. When the experiment was replicated, this rebound was even more pronounced for birds that had undergone a second period of 4 weeks in the small home cages. In contrast to the gradual decline in activity performance observed in the home cages, this rebound was virtually instantaneous. The possibilities are discussed that this rebound may result either from an increase in motivational tendency during the period of spatial restriction or from a response to an increase in novelty.

A case control study of on-farm risk factors for tail biting in pigs

Abstract Tail biting is an abnormal behaviour of pigs that is thought to have a multi-factorial origin. It is considered an unpredictable event on farms and is hard to reproduce experimentally. Therefore, a novel approach involving a case control study was used to investigate risk factors for tail biting on commercial units in England. Ninety-two pig farms across England were visited over a period of 11 months. At each visit, the owner or the manager of the unit was interviewed and the unit inspected. Data were recorded on standard forms. Farms were categorised into those that had tail biting in at least one pig in the past 6 months and those that had not. Univariate and logistic regression analyses yielded the following main results. Adding straw in the creep area once or more per day decreased the risk of tail biting 10-fold. Keeping grower pigs on partially or fully slatted floors versus solid floor increased risks of tail biting (odds ratio (OR)=3.2). Using a feeding system with five or more grower pigs per feed space increased risks of tail biting (OR=2.7). A stocking density during the growing phase of 110kg/m 2 or greater increased risks of tail biting (OR=2.7). Farms that belonged to a holding of five or more pig units had an increased risk of tail biting (OR=3.5). As the number of pens per stockman increased by one, the risk of tail biting increased 1.06-fold. Tail biting was also associated with the following disease and production information: as the P2 back-fat value increased by 1mm, the risk of tail biting decreased by 1.5-fold; post-weaning mortality above 2.5% was associated with a 3.9-fold increase in the risk of tail biting; presence of respiratory diseases was associated with a 1.6-fold increase in the risk of tail biting. Tail docking was associated with a three-fold increase in the risk of tail biting. This study has identified and quantified some management practices on commercial farms that can be changed to decrease the risk of tail biting in growing and finishing pigs.

The social transmission of information and behaviour

Abstract Social influences on established behaviour and on the acquisition of new information and behaviour are reviewed. Distinctions between social facilitation and contagious behaviour are drawn and suggestions for further research on contagious behaviour are made. Socially derived visual, olfactory and auditory cues are considered as important influences on behaviour and subsequent learning. The evidence supporting two potential mechanisms of social learning, i.e. stimulus enhancement followed by individual learning, and imitation, is reviewed in detail. It is argued that the functions of social learning are similarly heterogeneous and include motor skill acquisition, gathering of environmental information, and social conformity. Factors affecting the spread of socially acquired skills, including the social relationship between demonstrator and observer, are highlighted. Lastly, the few studies of social learning that have been conducted with domestic species are reviewed and potential applied goals that could stimulate further research in this area are suggested.

Leg disorders in broiler chickens: prevalence, risk factors and prevention.

Broiler (meat) chickens have been subjected to intense genetic selection. In the past 50 years, broiler growth rates have increased by over 300% (from 25 g per day to 100 g per day). There is growing societal concern that many broiler chickens have impaired locomotion or are even unable to walk. Here we present the results of a comprehensive survey of commercial flocks which quantifies the risk factors for poor locomotion in broiler chickens. We assessed the walking ability of 51,000 birds, representing 4.8 million birds within 176 flocks. We also obtained information on approximately 150 different management factors associated with each flock. At a mean age of 40 days, over 27.6% of birds in our study showed poor locomotion and 3.3% were almost unable to walk. The high prevalence of poor locomotion occurred despite culling policies designed to remove severely lame birds from flocks. We show that the primary risk factors associated with impaired locomotion and poor leg health are those specifically associated with rate of growth. Factors significantly associated with high gait score included the age of the bird (older birds), visit (second visit to same flock), bird genotype, not feeding whole wheat, a shorter dark period during the day, higher stocking density at the time of assessment, no use of antibiotic, and the use of intact feed pellets. The welfare implications are profound. Worldwide approximately 2×1010 broilers are reared within similar husbandry systems. We identify a range of management factors that could be altered to reduce leg health problems, but implementation of these changes would be likely to reduce growth rate and production. A debate on the sustainability of current practice in the production of this important food source is required.

Differential effects of increased stocking density, mediated by increased flock size, on feather pecking and aggression in laying hens

Six flocks of laying hens were housed in percheries at each of four stocking densities (6, 14, 22 or 30 birds m−2) from 14 to 30 weeks of age. Stocking density was manipulated by changes in flock size (72, 168, 264 or 368 birds) within percheries of the same floor and height dimensions. The pecking behaviour of birds was observed directly at 15, 22 and 30 weeks of age, and corrected for the number of birds in view. Egg production was recorded at 23 and 27 weeks of age, and plumage condition was scored at 30 weeks of age. At 23 weeks of age, egg production was greater at 6 birds m−2 than at other stocking densities. The plumage condition of the birds was best at 6 birds m−2 and worsened with increased flock size and stocking density. The behavioural observations suggested that this was due to an increase in mild feather pecking with increased flock size and stocking density. Mild feather pecking increased with bird age and was most frequently observed on the perchery floor although, at higher flock sizes and stocking densities, it also occurred on the perches. Severe feather pecking was infrequent, especially at the lower flock sizes and stocking densities, but was most likely to occur near the nest boxes. Vent pecking was extremely rare. Aggressive pecking was most common in the smaller flocks at the lowest stocking densities, possibly because these birds attempted to form social hierarchies. Birds in the larger flocks at higher densities appeared to adopt non-social, non-aggressive behavioural strategies.

Cross-sectional study of the prevalence of feather pecking in laying hens in alternative systems and its associations with management and disease.

A cross-sectional study of risk factors for feather pecking in layings hens in alternative systems was carried out in July 1998. A total of 637 questionnaires were sent out to farmers and producer groups and, after two reminders, the final response rate was 51.5 per cent. The outcome variable was feather pecking after point of lay. Over 55 per cent of the farmers reported that feather pecking had occurred in the last depopulated flock. This outcome was compared with the management procedures reported by flock managers by using univariate statistics. Factors associated with feather pecking with a significance ≤0.05 were then tested in two logistic regression models. In the first model the following factors were associated with an increased risk of feather pecking: less than 50 per cent of the flock using the outdoor area on a fine and sunny day, the occurrence of egg peritonitis and the occurrence of infectious bronchitis. The direction of the association between feather pecking and these infectious diseases was unclear, so in the second model only factors which were consistent throughout the laying period were tested. The following factors were associated with an increased risk of feather pecking: less than 50 per cent of the flock using the outdoor area on a fine and sunny day; three or more changes of diet during lay; the inspection of the flock by one person; an absence of loose litter at the end of lay; a temperature in the hen house of less than 20°C; turning the lights up when the flock was inspected; and the use of bell-drinkers. It is concluded that some of these factors could inhibit foraging and dust-bathing behaviour and others may increase competition or frustration, both of these changes having been shown experimentally to initiate feather pecking behaviour.

Behavioural needs, priorities and preferences of laying hens

We review the behavioural needs, priorities and preferences of laying hens for increased space, perching, nesting, foraging and dustbathing behaviour. Hens make full use of and may work to gain access to perches, however it is not yet known how perching ranks in comparison with other behaviours. Laying hens appear to have an instinctive need to perform pre-laying (nest-building) behaviour and have a strong preference for a discrete, enclosed nest site, for which they will work hard to gain access as oviposition approaches. Access to a nest site is a high-ranking priority for laying hens, preferred over food at this time. Foraging is a behavioural need, with peat, sand and wood shavings preferred substrates in choice experiments. There is no reduction in time spent foraging when a cost is imposed, nor when feed is freely available. Dustbathing is currently viewed as a behavioural need, as the extent to which hens value dustbathing is not known. Bird preferences for space are complex and confounded by interactions between group size and stocking density. There is some evidence that priority for space varies during the day and increases when the total space available to a group of birds is restricted, and that greater priority is given to space than to small group size. The presence of apparently purposeless behaviour, of high levels of aggression or redirected behaviours such as feather pecking and cannibalism are indicators that the housing system is not meeting the behavioural needs of the hens and hence is not satisfactory for bird welfare.

Factors affecting the prevalence of foot pad dermatitis, hock burn and breast burn in broiler chicken

1. Standardised data on flock husbandry were recorded on 149 broiler farms during the 4 d prior to slaughter. 2. Birds were examined at the slaughterhouse for contact dermatitis lesions. Foot pad dermatitis score (FPDS) and hock burn score (HBS) were measured on five point scales. Carcase rejection data were also collected. 3. The mean percentage of birds in each flock with: moderate or severe foot lesions was 11·1% (range 0–71·5%); moderate or severe hock burn was 1·3% (range 0–33·3%); and, breast burn was 0·02%. 4. A general linear model was developed to examine factors associated with mean flock FPDS. Assuming a linear relationship, within the range of data collected and with all other factors remaining the same, every 1% increase in the proportion of Genotype A birds in the flock was associated with an increase in mean FPDS of 0·003, every one-point increase in litter score was associated with a 0·326 increase in mean FPDS and every one-point increase in flock mean HBS was associated with a 0·411 increase in mean FPDS. Flock mean FPDS was associated with feed supplier and was higher in winter. 5. The general linear model developed for flock mean HBS, found that every one-point increase in mean FPDS increased mean HBS by 0·090, every one-point increase in litter score increased HBS by 0·119 and, every 1% increase in small/emaciated birds decreased mean HBS by 0·333. Reduced HBS was also associated with increased final litter depth, younger slaughter age and an increased percentage of dietary wheat. For every 1% increase in Genotype A birds, a decrease in flock mean HBS of 0·003 would be expected. 6. An effect of hatchery was also identified.

Equine learning: progress and suggestions for future research

Abstract Horses are well able to form classical and instrumental associations and so the focus of much recent research has been on the stimulus control of instrumental learning. Horses appear to discriminate using spatial cues more easily than other stimulus features, as indicated both by the speed of initial task acquisition and by the extent to which acquired discriminations can be reversed. Phenomena associated with discrimination learning in laboratory animals, including generalisation and peak shift, have been demonstrated in horses. However, the ability of horses to classify stimuli into categories is more controversial. Although there is some evidence that horses may be able to form categories based on similarities in the physical appearance of different stimuli, there is currently no evidence that they are able to develop abstract concepts. Their performance on social learning tasks has also been poor. Few correlations are observed between the learning ability of individual horses on different tasks, suggesting that it may not be possible to classify individual horses as ‘good’ or ‘poor’ learners. Better learning performance by horses that are naturally calm is probably due to reduced interference in the learning process. Correct handling procedures can lower reactivity levels in horses, and may facilitate learning in some circumstances. Future research on equine learning needs to take into account the complex nature of equine social interaction. Studies on the effects of stress on learning, and on social and spatial cognition, are also particularly needed.