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

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 (NH4Cl) treatment. However, the outcome of urine acidification and the physiological responses to short-term NH4Cl supplementation under respiratory hypocapnia of HTa have rarely been reported. The present study investigated the effect of NH4Cl 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 CO2 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.

High Dietary Cation and Anion Difference and High-Dose Ascorbic Acid Modify Acid–Base and Antioxidant Balance in Dairy Goats Fed under Tropical Conditions

“…These levels of the afternoon Ta and ΔTa conditions were comparable to the HTa of tropical conditions [ 1 , 2 , 3 ] that could activate physiological mechanisms and affect milk production. This was supported by the responses from RR, Tr, and WI that were in line with our previous results and indicated the activation of heat dissipation [ 2 , 3 , 4 ]. It appears likely that the responses were sufficient for acid–base imbalance (i.e., sporadic respiratory hypocapnia), depleted antioxidants and decreased mammary gland function in dairy goats and cows [ 1 , 2 , 3 ].…”

“…The kidney function that regulates urine pH was activated during the second 4 weeks of the present experiment. This is in contrast to when goats were given a low DCAD regimen [ 4 ] and indicated the threshold of kidney function in terms of acid and base regulation. Specifically, a low DCAD regimen or acid load [ 4 ] could activate kidney function faster than a high DCAD regimen or bicarbonate load.…”

“…This is in contrast to when goats were given a low DCAD regimen [ 4 ] and indicated the threshold of kidney function in terms of acid and base regulation. Specifically, a low DCAD regimen or acid load [ 4 ] could activate kidney function faster than a high DCAD regimen or bicarbonate load. A high dose of AA supplementation influenced systemic acid–base balance by decreasing urine pH.…”

“…This HTa effect can be observed with the activation of evaporative heat dissipation by panting and antioxidant defense [ 2 ]. The excess of both responses can lead to acid–base imbalance and oxidative stress [ 3 , 4 , 5 ] which may indirectly alter mammary gland function. However, research on mammalian cells has shown that HTa could directly affect cell metabolism, and oxidative stress has been proposed to mediate this effect [ 6 ].…”

“…During the daytime, the natural HTa increased rectal temperatures (Tr), respiratory rate (RR), and plasma cortisol [ 10 ]. The excess HTa response could induce acid–base imbalance and cause respiratory hypocapnia in goats [ 3 , 4 , 5 , 9 ]. Blood bicarbonate (HCO 3 ) was decreased to compensate for this respiratory acid–base imbalance [ 11 ].…”