The Requirements and Role of Potassium in Ovine Nutrition

The role of potassium in ovine nutrition was investigated by using 76 western range lambs in a 56-day feeding trial, a 56-day equalized feeding trial, and two 30-day balance trials. A semipurified ration (.046% potassium) was used and potassium was added as K2CO3. The level of potassium necessary to promote optimum feedlot performance was between 0.3 and 0.5% of the air-dry ration. A marked decrease in appetite was observed in lambs consuming a ration containing 0.1% potassium compared with one containing 0.5% potassium. Lambs receiving a ration containing 0.7% potassium gained significantly (P < 0.05) more body weight than lambs receiving a 0.3% potassium ration in the equalized feeding trial. Results of the balance studies suggested that the daily potassium maintenance requirement was less than 56.1 meq (63.6 mg/kg body weight). Low potassium intakes resulted in significantly (P < 0.05) lower serum levels of potassium and phosphorus with little change in serum sodium, calcium, magnesium, or chloride. Potassium depletion also resulted in a decrease in skeletal and heart muscle potassium and an increase in liver potassium. Apparent intestinal absorption of sodium was impaired by a relatively high dietary level of potassium (94.4 meq daily) while lower levels of potassium resulted in increased urinary sodium losses. Nitrogen balance was decreased when a low level of potassium (13.7 meq daily) was fed; however, potassium intake had no effect on apparent digestibilities of nitrogen, dry matter, or energy.