Effect of cage area, cage height and perches on feather condition, bone breakage and mortality of laying hens.

1. The health of 2 flocks of 896 ISA Brown laying hens were studied successively over the years 1995 and 1996 under different caging conditions. Hens were kept in groups of 4 in a total of 224 cages. The treatments (7 different types of cages) differed in area per hen (450, 600 or 800 cm2) and height (40 or 60 cm). In the large (800 cm2/hen) and high (60 cm cage) treatment, half of the cages were equipped with perches (20 cm/hen). Each study lasted 48 weeks. 2. Feather condition was found to be independent of cage type. 3. No differences were apparent between the 7 treatments in tibia breaking strength (using the 3-point breakage technique). A significant increase in humerus breaking strength was observed in the high cages. The frequency of broken wings recorded after slaughter was lower in high cages (23%) than in low ones (36%). 4. Mortality was different between treatments. This was explained by a higher proportion of birds killed by 'body cannibalism' in the 60 cm high cages, and by a higher proportion of birds killed by 'vent cannibalism' in the cages with perches.