SOME EFFECTS OF DIETARY POTASSIUM UPON DIGESTIBILITY, SERUM ELECTROLYTES AND UTILIZATION OF POTASSIUM, SODIUM, NITROGEN AND WATER IN HEIFERS

Abstract

Balance studies were conducted with heifers weighing between 210–258 kg to determine effects of different dietary potassium levels, 156.6 (low), 439.4 (medium) and 1,086.8 (high) meq upon nutrient utilization. The low potassium ration produced an average negative potassium balance of 25.2 meq daily, while the other rations produced positive potassium balances. Urinary potassium excretion was markedly affected by potassium level while fecal potassium excretion was much less affected: in general, the higher the potassium intake, the higher the urinary and fecal potassium excretions. All heifers were in positive sodium balance and dietary level of potassium did not significantly influence either urinary or fecal excretion of sodium. Nitrogen balance was not significantly affected by treatment, but urinary ammonia excretion was significantly (P < 0.01) higher when the low potassium ration was fed. Water consumption and urine volume were significantly (P < 0.01) higher for the heifers fed high potassium, but water balance was not affected. Apparent digestibilities of energy, dry matter, nitrogen, crude fiber and ether extract were not significantly affected by treatment.Serum potassium levels were lower (P < 0.05) and phosphorus higher (P < 0.05) in heifers receiving the low than in heifers receiving the high level of potassium. Serum concentrations of sodium, chloride, calcium and magnesium were not significantly affected by dietary potassium.From the data, the potassium requirement for maintenance of the heifers was estimated to be 133 meq potassium daily per 100 kg body weight.