Hypocalcemic development in high and low calcium-adapted chicks during acute calcium deficiency

Chickens were adapted to either a high or low calcium intake and then subjected to an acute calcium deficiency by feeding ground yellow corn +/- phosphate. Hypocalcemia developed within 3-5 h in those chicks given the corn plus phosphate. The response was about equal in the high and low adapted animals suggesting that the effect was not mediated via regulatory factors such as parathyroid hormone or thyrocalcitonin intervention. Rather, it is suggested that the influence of phosphate is direct and may be due to an enhancement of calcium movement from the fluids to the bone. The high calcium adapted chicks also exhibited some hypocalcemia in response to eating corn without phosphate supplementation. This development, contrary to the other cases, appeared to be due to a lag in calcium regulating mechanisms. The low calcium adaptation did not seem to influence growth within the timespan used, but there was a significant reduction in bone ash values and of adrenal enlargement. Thus, it was evident that the low and high calcium diets were different in regards to calcium metabolism and it appears that the low calcium intake may have been stressful.