Effects of selected minerals on acid-base balance and tibial dyschondroplasia in broiler chickens.

Experiments were conducted to determine the relative acidogenicities of several anions, including chloride, sulfate, and mono-, di-, and tribasic phosphate in commercial broiler chickens. Graded levels (80 and 160 meq/kg of diet in two experiments; 50, 100, and 150 meq/kg in a third experiment) of all anions were substituted as calcium salts on a molar equivalent basis for calcium carbonate in a semipurified diet. All diets contained equivalent amounts of calcium. The occurrence of tibial dyschondroplasia was determined by visual scoring of the epiphyseal growth plate in the distal end of the tibiotarsus. None of the anions added to the diet at levels of 160 meq/kg or less affected body weight or feed consumption. A higher level of chloride (240 meq/kg) that was utilized in some experiments decreased weight gain by 16 to 22%. All anions except tribasic phosphate resulted in reduced blood pH or bicarbonate concentrations or both. Monobasic phosphate was more acidogenic than dibasic phosphate and sulfate and chloride was the most acidogenic of all mineral anions. All anions including tribasic phosphate increased the severity of tibial dyschondroplasia. There was no consistent relationship between blood pH, bicarbonate concentration, or partial pressure of CO2 and the severity of tibial dyschondroplasia.