G.M. CRONIN1
J.A. DOWNING2
V. JANARDHANA3
J.W. LOWENTHAL3
K.L. BUTLER4
1Animal Welfare Science Centre, Department of Primary Industries, Werribee, VIC, Australia
2Faculty Veterinary Science, University of Sydney, Camden. NSW, Australia
3CSIRO, Livestock Industries, AAHL, Geelong, VIC, Australia
4Department of Primary Industries, Werribee, VIC, Australia
The effects of housing hens at 8/cage at space allowances of 750 and 1500 cm2/hen and 16/cage at 750 cm2/hen were examined from 29-36 weeks of age. A range of behaviour observations and physiological and morphological measurements were made. Hens housed in groups of 16 had higher corticosterone concentrations in eggs and a lower immune response compared to groups of 8 hens at 1500 cm2/hen. Within the range of treatments used, group size had a greater potential impact on welfare than space allowance.
Results and discussion
Despite the presence of furnished cages in the market place and the considerable support for such designs of cage, particularly in Europe, there has been little comprehensive assessment of hen welfare as a consequence of such furniture. This preliminary experiment examined the effects of housing hens at eight/cage with a space allowance of 750 and 1500 cm2/hen and 16/cage with a space allowance of 750 cm2/hen, as part of a larger experiment on the welfare of hens in furnished cages.
The larger experiment involved 20 treatments using 66 Victorsson cages in a controlled environment shed, maintained at 17-23°C with a 16:8 h light:dark cycle and a light intensity of 20 lux that was decreased to 5 lux at 28 weeks of age, due to a slight increase in cannibalism. The cages were 1.2 x 0.5 m (width x depth) and 0.45 m high at the rear.
1500 cm2/hen was provided by removing the panel between 2 cages ie. 2.4 m width. The experimental design was a 3 (nest box) x 3 (dust bath) x 2 (perch) factorial + 2 added controls (space and group size) in a rectangular lattice. The experimental unit was the cage and all cages were sampled during an 8-week period commencing at 29 weeks of age. There were 3 and 54 replicates for the double and single cage treatments, respectively. The following samples and measurements were taken: video observations for timing of egg laying, blood for immunology, blood and eggs for corticosterone concentrations, as measures of stress, body weight, claw length and scores for feather damage and cover, foot condition, pecking wounds/injuries and keel bone deformation, as measures of injuries and body condition.
Only data close to or <P=0.05 are tabulated. Group size and space allowance had no effects on the majority of the observations and measurements (P>0.05). In the 16 hen, double cage treatment corticosterone concentrations in egg albumen were higher (P=0.021), adrenal responsiveness to exogenous ACTH was reduced (P=0.034) and the ability of cells to produce IL-6 was reduced (P=0.051).
This experiment showed evidence of both stress and immunosuppression in the large group size treatment, presumably due to social factors, although this was not examined in this preliminary experiment. The data presented and other data on corticosterone concentrations make it equivocal whether the stress response was an acute or a chronic response. Further research on space allowance and group size is clearly warranted.
From Proceedings of the "17th Australian Poultry Science Symposium", New South Wales, Australia.
