Studies on High Intakes of Various Sulphate Salts and Sulphuric Acid in Sheep: 3. Effects on the Metabolism of Sodium, Potassium, Magnesium, Calcium, Chloride and Phosphate and on Acid-Base Balance

In a Latin square experiment the metabolism of sodium, potassium, magnesium, calcium, phosphorus and chloride were studied in five sheep fed a pelletted grass meal diet alone or supplemented with sodium sulphate, sodium bisulphate, ammonium bisulphate or ammonium sulphate, each equivalent to 1% sulphur in the feed dry matter. Each diet was fed ad lib for 12 days, then at a restricted intake for 11 days, followed by a 6-day recovery period on the grass meal only. Treatment had no effect on serum levels of any of the electrolytes, each remaining normal throughout the experiment. The extra sodium provided by sodium sulphate and sodium bisulphate was largely excreted in the urine, though it also increased faecal output and retention. Ammonium bisulphate and ammonium sulphate increased urinary sodium excretion for the first 6 days, but otherwise had no effect on sodium metabolism. The only significant treatment effect on potassium metabolism was a decrease in faecal excretion caused by both sodium sulphate and sodium bisulphate. Ammonium bisulphate and ammonium sulphate significantly increased urinary magnesium excretion while all treatments slightly decreased faecal magnesium excretion. Urinary calcium excretion was increased substantially by sodium bisulphate and to a greater extent by ammonium bisulphate and ammonium sulphate, but there was no significant treatment effect on retention or faecal excretion of calcium. Both ammonium bisulphate and ammonium sulphate caused a slight negative balance of phosphorus, otherwise there was no treatment effect on phosphorus metabolism. Two of the five sheep excreted much more phosphorus in urine and correspondingly less in faeces than the other three, but this did not improve their tolerance for the acid diets. Treatment did not affect chloride metabolism. The balance of acid on the treatments which induced acidosis was positive on each treatment especially for the first 4 days, the values being greater on ammonium bisulphate and ammonium sulphate than on sodium bisulphate. During the recovery period the balance of acid was negative on each treatment with the value decreasing towards the end of the 6 days. Sulphuric acid was fed in the same way to the five sheep for 23 days immediately after the foregoing experiment. Its effects on electrolyte and acid-base metabolism were similar to those of ammonium bisulphate and ammonium sulphate.