BONE STRENGTH OF LAYING HENS KEPT IN AN ALTERNATIVE SYSTEM, COMPARED WITH HENS IN CAGES AND ON DEEP-LITTER

Observations of vigorous wing movements and measurements of bone strength were compared in two experiments with birds in three different housing systems: A semi-intensive alternative system under development, a battery cage system and a deep-litter system. A significant effect of housing system on the frequency of vigorous wing movements was found. The highest frequency was seen in the deep-litter system, about half this number in the alternative system, while in the battery cages they were never observed. Corresponding to this a reduction in humerus strength of 9% was found in hens from the alternative system and of 45% in hens from cages, compared with deep-litter. A reduction in tibial breaking strength was also found in caged hens, when compared to deep-litter hens. Keeping hens in cages thus restricts their movements, especially wing movements, to the degree that bone strength is greatly reduced. This has welfare implications, for hens with low bone breaking strength risk a possibility of breakage, especially when handled and transported. When alternative systems are designed opportunities for movement in the three dimensions should be considered. © 1990, Taylor & Francis Group, LLC. All rights reserved.