BONE-STRUCTURE AND BREAKING STRENGTH IN LAYING HENS HOUSED IN DIFFERENT HUSBANDRY SYSTEMS

1. Bone structure and breaking strength were measured in hens that had been housed throughout a laying year in battery cages or in Perchery, Naturel or Litter and Wire husbandry systems. 2. Battery caged hens had the poorest bones, as assessed by measurements of cancellous bone volume, radiographic density, cortical thickness and three-point breaking strength. 3. Humeri from birds in the Litter and Wire system were less dense radiographically and weaker than those from Perchery or Naturel birds but leg bone characteristics were similar with these three systems. 4. There were no differences in bone characteristics between birds in Perchery and Naturel systems. 5. There were strong correlations between radiographic densities and strengths of contralateral humeri and tibiae over all husbandry systems. Humerus structural and strength characteristics may be the best criteria of osteoporosis in hens. 6. It is concluded that the extent of movement allowed by different husbandry systems affects structural bone loss and bone strength in laying hens. 7. It is further concluded that the breaking strength of a hen's bone is closely related to morphometric measures and radiographic density of its structural components.