Effects of Low Dietary Cation and Anion Difference on Blood Gas, Renal Electrolyte, and Acid Excretions in Goats in Tropical Conditions

SIMPLE SUMMARY: Urinary tract obstruction is a common problem in male goats. Urine acidification resulting from ammonium chloride treatment has been proved to dissolve sandy stones in alkaline urine. Although the natural high ambient temperature of the tropical area activates acid-base balance to alkalosis direction, a low dietary cation-anion difference regimen could acidify goat urine. The tubular excretion of acid and electrolytes plays a crucial role during mixed acid-base situations: respiratory alkalosis and metabolic acidosis. ABSTRACT: Goats can suffer from intermittent heat stress in high ambient temperature (HTa) conditions, which causes sporadic respiratory hypocapnia. Obstructive urolithiasis is a common urological problem in goats. Sandy uroliths can be partially relieved by urine acidification with short-term ammonium chloride (NH(4)Cl) treatment. However, the outcome of urine acidification and the physiological responses to short-term NH(4)Cl supplementation under respiratory hypocapnia of HTa have rarely been reported. The present study investigated the effect of NH(4)Cl supplementation that produced a low dietary cation-anion different (l-DCAD) diet on acid-base balance and renal function under HTa conditions. The first experiment investigated the physiological responses to natural HTa to prove whether the peak HTa during the afternoon could induce HTa responses without a change in the plasma cortisol. The partial pressure of CO(2) also tended to decrease during the afternoon. The second experiment examined the short-term effect of l-DCAD under HTa conditions. Although the blood pH was within the normal range, there was a clear acid-base response in the direction of metabolic acidosis. The major responses in renal function were an increase in tubular function and acid excretion. With a comparable level of creatinine clearance, the fractional excretions (FE) of chloride and calcium increased, and the FE of potassium decreased. Acid excretion increased significantly in the l-DCAD group. We conclude that under HTa conditions, the tubular excretion of electrolytes and acids was the major response to acid loading without changing the filtration rate. The l-DCAD formulation can be used to acidify urine effectively.