Abstract
Calcium metabolism in the temperature stressed domestic chicken and turkey was examined by (1) studying the effects of brooding temperature, dietary phosphorus and molybdenum on bone mineralization in 10-day-old turkey poults, (2) assaying for renal 25-hydroxycholecalciferol-1-hydroxylase (25-HCC-1-hydroxylase) in one to 21-day-old poults and (3) assaying for intestinal calcium-binding activity in heat stressed laying hens. A review of pertinent data on 25-HCC-1-hydroxylase activity in heat stressed laying hens is also included. Bone mineralization (percent tibial bone ash) was significantly increased (p < .05) in 10-day-old poults brooded at 31 C versus poults brooded at 35 C. Further lowering the brooding temperature to 29 C did not significantly increase bone mineralization, however. A significant (p < .05) temperature-by-diet interaction in regard to percent bone ash occurred in one experiment when poults were brooded at 29 C and 35 C. In this experiment, poults fed 1.2 percent total phosphorus had significantly higher (p < .05) bone ash at 35 C rather than 29 C. Poults fed both 1.0 and 1.2 percent total dietary phosphorus had significantly higher (p < .05) percent bone ash than poults fed 0.6 and 0.8 percent total phosphorus. Bone ash was significantly correlated (p < .05) with serum phosphorus, but not serum calcium. Poults brooded at 35 C and fed a diet supplemented with 5 ppm molybdenum (8 ppm total) had significantly greater bone ash than poults receiving the control (non-supplemented) diet. In another experiment, there was a significant (p < .05) temperature-by-diet interaction in regard to both bone ash and serum phosphorus. Percent bone ash and serum phosphorus were both significantly lower (p < .05) in the molybdenum supplemented poults brooded at 29 C, but higher at 35 C. Renal 25-HCC-1-hydroxylase was active in poults ranging from one-day to 21-days of age. Renal 25-HCC-24-hydroxylase, however, was not active in the one-day-old poult, but was active in the 7, 14, and 21-day-old poult. Intestinal homogenates from heat-stress laying hens had significantly higher (p < .05) calcium-binding activity than homogenates from non-heat-stressed hens, probably due to vitamin D-dependent calcium-binding protein synthesized in response to increased renal 25-HCC-1-hydroxylase activity.
Bailey, Christopher Anthony (1982). The metabolism of calcium in temperature stressed Gallus domesticus and Meleagris gallopavo. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -361660.