The effect of dietary supplementation with 1,25-dihydroxycholecalciferol or vitamin C on the characteristics of the tibia of older laying hens

Seventy-two-week-old Leghorn hens were fed a conventional corn-soybean meal diet, or comparable diets either devoid of all supplemental vitamins, or with additions of 5 mu g/kg 1,25-dihydroxycholecalciferol [1,25(OH)(2)D-3], or 100 ppm vitamin C. The diets were fed for up to 30 d, with periodic observation on bone characteristics of selected birds. With a vitamin-deficient diet it took 30 d to realize significant reductions (P < 0.05) in bone breaking strength and these birds had less bone ash as early as 15 d (P < 0.05), although bone calcium content was not affected. Adding 1,25(OH)(2)D-3 to the diet caused an increase in bone breaking strength after 15 d (P < 0.05) in the vitamin-deficient birds, although no difference was seen after 30 d. This increase in bone strength was associated with increase in bone cross-sectional area. Vitamin C generally had little effect on bone characteristics of the bird. These results suggest that there is little bone remodeling of older laying hens in response to short-term feeding of 1,25(OH)(2)D-3 or vitamin C.