Relationships between dietary and plasma concentrations of calcium and phosphorus in intact and...

Two experiments were conducted with cockerels to determine whether the presence or absence of the ultimobranchial glands would influence the relationship between dietary and plasma calcium and phosphorus. Broiler type cockerels, 16 weeks of age which had been sham operated (SHAM) or ultimobranchialectomized (UBX) 1 to 3 weeks earlier, were fed diets containing 0.8 or 2.4% calcium and 0.13 to 0.33% phosphorus. The SHAM cockerels fed diets containing 0.8% Ca and 0.13% P did not develop hypercalcemia whereas the UBX cockerels fed this diet developed slight significant hypercalcemia after 17 to 21 days. In Experiment I, SHAM cockerels fed the diet containing 2.4% Ca and 0.13% P developed mild, chronic hypercalcemia (12.7 mg./100 ml.) with a plasma phosphorus of 3.03 mg. P/100 ml., whereas the UBX cockerels fed the same diet developed severe hypercalcemia (16.0 mg./100 ml.) and hypophosphatemia, 1.68 mg. P/100 ml. In Experiment 2 the following plasma values were observed after 17 days of consuming the experimental diets: SHAM fed 2.4% Ca and 0.13% P had 10.6 mg. Ca/100 ml. and 3.59 mg. P/100 ml., whereas UBX fed the same diet had 12.8 mg. Ca/100 ml. and 2.24 mg. P/100 ml. The UBX fed 2.4% Ca and 0.33% P for 17 days had plasma values of 10.8 mg. Ca/100 ml. and 4.48 mg. P/100 ml. It is concluded that the presence of the ultimobrancial glands are essential to the regulation of plasma calcium and phosphorus in chickens which consume high calcium-low phosphorus diets.