Movement of Caged Laying Hens

Concern for the welfare of laying hens housed in conventional battery cages, a behaviourally restrictive housing environment, is growing, and an increasing number of producers are preparing to transition to alternative housing systems such as furnished cages. However, converting to new housing systems is not as simple as placing hens into them and being rewarded with good welfare and high production. Although furnished housing provides more behavioural freedom, it presents other challenges.

To address the challenges of intensive and competitive production in these alternative cage environments, Dr. Michelle Jendral and her research team at the Nova Scotia Agricultural College have been evaluating laying hen production in furnished cage systems. Their overall goal has been to compare production, physiological, behavioural and condition parameters of three laying hen strains: Lohmann Brown (LB), LL (LL) and Shaver White. The hens were housed in conventional battery and furnished large group cages over two production cycles, to assess hen health, welfare and productivity in, and strain suitability to, the different housing environments.

Included in this large, multidisciplinary study was an assessment of the prevalence and severity of osteoporosis and bone fractures, as determined from the incidence of breaks during the production cycle and after processing, as well as the bone breaking strength at end of cycle, feed consumption, egg production and quality, and calcium metabolism efficiency during the production period. Behaviour was monitored through live observation and digitally recorded footage to quantify hen prelay and nesting behaviour, dustbathing and amenity use, aggression, stereotypies, comfort and locomotory activity. Condition of the integument was monitored to further assess hen health, and blood white cell counts and tonic immobility were conducted to assess hen stress and fear.

Their findings? In contrast to previous findings in Dr. Jendral’s laboratory, when hens were housed at 450 cm² in furnished and conventional cages, the current study housed birds at 660 cm², and no treatment differences in femoral or tibial bone breaking strength were found. The increased floor space allowance in the current trials may have encouraged sufficient static walking activity in conventional cages to contribute to structural bone preservation. Notably, treatment differences in furcula, keel, pubis, wing and leg bone fractures were largely absent throughout the production periods, possibly reflecting the positive impact of increased floor space provision on structural bone preservation. However, humeral breaking strength values were lower in conventional than in furnished cages, suggesting that providing increased cage height and raised amenities such as perches and a dustbath, which increase hen opportunity for wing movement, is necessary to maintain humeral architecture in caged hens. Furthermore, a high incidence of processing-related fracture was seen in both housing treatments, suggesting that cumulative structural bone loss remains a concern in commercial strains, and that genetic selection for birds that are better able to preserve structural bone should remain a priority. In the more prohibitive conventional cage environment, lighter hybrid strains were also more susceptible to osteoporosis. Importantly, both humeral and femural bone data from this study support the provision of increased floor space and cage height above current national standards.

Despite findings that hens housed in furnished cages at 450cm² consume more feed than hens housed in conventional cages at the same density, housing treatment differences in feed consumption were not observed in the current flocks.

This suggests that at a greater floor space provision, freedom of movement is increased in both systems, and movement is sustained through similar energy intake. Notably, in both housing systems, and at all ages, LB hens consumed the most feed, followed by LL and then Shaver White hens.

Strain differences in body weight were apparent in both conventional and furnished cages at both peak and late production, with LB hens weighing the most on average, followed by LL and Shaver White. Significant changes in body weight, primarily observed for LB hens, emphasize the importance of group size, management and housing interaction on bird health.

Treatment differences in egg production and quality were largely absent. In both systems, LB hens produced heavier eggs than Lohmann White and Shaver White hens and had stronger shells, and LB and Shaver White hens appeared to better maintain shell thickness with age than LL. Overall, eggs from LB and Lohmann White hens were found to be stronger than those from Shaver White. Since Jendral et al. (2008) previously observed treatment differences in egg quality when hens were housed in furnished cages and conventional cages at 450 cm² usable floor space, but did not in this study, in which hens were housed at 660 cm², bone and egg findings from the current research suggest that increasing floor space allocation for caged hens contributes to both bone and egg quality.

Prelay behavioural findings indicate that provision of a nest box in furnished cages permitted expression of normal nesting activity, resulting in an overall decrease in hen frustration. As a result, hens showed increased expression of comfort behaviour, which was likely facilitated by the higher cage height in furnished cages and the additional floor space created in the cage area when the nest box was in use. Reduced aggressive pecking in general, and reduced feather pecking for LL hens, was also observed in furnished cages. High levels of and variation in displacement activity in both systems suggest that nesting was frustrated in conventional cages, and that competition for the nest space did occur in the large group furnished cages, as also evidenced from some nesting in the cage area in furnished cages.

Despite the competition for the dustbathing space in large group furnished cages, as evidenced by aggressive pecking in all strains and reduced bathing activity by larger LB birds, hens in these cages used the facility to express dustbathing and foraging behaviours. The provision of a dustbath in which the smaller LL and Shaver White hybrids could dustbathe, and the larger LB hybrids could predominantly forage, likely minimized the expression of feather pecking behaviour. Dr. Jendral believes these findings provide evidence that foraging and dustbathing are highly motivated behaviours, and permitting hens to express these activities mitigates the performance of redirected damaging behaviours. Amenity space provision, design and timing of substrate delivery must be further examined to reduce competition for bathing and foraging facilities in cage environments.

Total feather condition did not differ between treatments early in the production cycles; however, treatment and strain differences were apparent with age. Also, considerable variation in individual hen feather cover existed within the cages. In furnished cages, this was likely reflective of the large and potentially unstable group size, which from the behavioural data, appears to have led to competition for amenities, and feather pecking of subordinate birds.

In conventional cages, frustrated nesting activity, as evidenced from the prelay behavioural data and redirected foraging and bathing activity, likely contributed to feather pecking. In general, hens in furnished cages had improved back, breast and wing condition over conventionally caged hens, which provides evidence that despite the large and likely unstable group size, provision of amenities in furnished cages permitted behavioural expression that reduced frustration and redirected feather pecking activity. High variability in hen condition in furnished cages combined with the absence of treatment differences in hen stress and fear response provide additional evidence that, despite increased freedom of behavioural expression in furnished cages, the large group size in furnished cages is nonetheless contributing to hen stress.

The findings from this research provide compelling evidence for the production and welfare benefits conferred by providing caged hens with adequate space and amenities to express natural and load-bearing activities. Variation in individual hen and overall strain response to large group housing suggests that further studies examining group size, in combination with stocking density, strain analyses and amenity design must be conducted. Layer breeding programs must also continue to be adapted to select against metabolically and environmentally induced disorders. To read more, please visit www.poultryindustrycouncil.ca.

Featured Researcher

Michelle J. Jendral completed her PhD in Animal Science in August 2008, at the University of Alberta. The focus of her doctoral research concerned the development of sustainable cage and non-cage housing systems for laying hens that balance hen productivity, health and well-being. Currently, Michelle is an assistant professor, Poultry Behaviour and Welfare, at the Nova Scotia Agricultural College in Truro, N.S., where she is continuing her research in laying hen housing systems. Additional research interests include production and welfare issues facing the poultry industry, poultry behaviour, neuroethology and cognitive processes, and the importance of the human-animal interaction in animal production. Michelle teaches courses in domestic animal behaviour, avian biology, avian production systems, applied ethology and animal welfare.