STUDIES ON EFFECTS OF NUTRITIONAL FACTORS ON BONE-STRUCTURE AND OSTEOPOROSIS IN LAYING HENS

1. A modern hybrid strain of laying hen (Hisex) was fed from point of lay to 68 weeks on a control diet and diets containing oystershell, fl uoride, 1,25-dihydroxycholecalciferol, ascorbic acid, a lower concentr ation of phosphorus and a combination of a lower concentration of crud e protein and higher concentration of vitamin K. Hens from a much olde r strain (Brown Leghorn J-line) were fed on the control diet. 2. Plasm a variables were measured during lay. End-of-lay trabecular and medull ary bone volumes in the proximal tarsometatarsus and free thoracic ver tebra were measured by histomorphometry. 3. The majority of Hisex hens were considered to be osteoporotic by tile end of lay. In contrast, n one of the J-line were osteoporotic. 4. None of the nutritional treatm ents affected trabecular bone volumes. Medullary bone volumes were inc reased significantly by feeding oystershell or fluoride. 5. There was no phenotypic correlation between egg production and trabecular bone v olume in the Hisex hens. 6. The experiment provided evidence that oste oporosis in laying hens, as assessed by trabecular bone volumes, is no t caused by calcium deficiency and could not be prevented by any of th e nutritional treatments studied.