Influence of dietary electrolytes on digestive tract pH and acid-base status of chicks

The nutritional interaction of lysine and arginine is affected by the electrolyte balance of the diet. Because the ionization and, therefore, the transport and metabolism of these amino acids may be affected by the pH of fluids in which they are dissolved, the present study was conducted to determine the effect of dietary electrolytes on the pH of the digestive tract and the acid-base status of the chicken. A purified casein diet deficient in arginine was modified by addition of either KHCO3 or CaCl2 X 2H2O at levels sufficient either to alleviate or to exacerbate the lysine-arginine antagonism. Addition of KHCO3 led to a more alkaline diet than the arginine-deficient control while CaCl2 X 2H2O resulted in a more acidic diet. Varying the electrolyte balance had little effect on digestive tract pH. The pH of the crop was depressed (P less than .05) by dietary Cl-, but neither Cl- nor K+ had an effect on the pH of the proventriculus, duodenum, or middle and distal portions of the small intestine (P greater than .05). Dietary Cl- significantly depressed plasma bicarbonate, base excess, and PCO2 (P less than .05) but did not significantly decrease plasma pH (P greater than .05). These same acid-base parameters were unaffected by addition of K+ to the control diet. It is concluded that variations in dietary electrolytes affect the acid-base balance of the chicken and alter the pH of the crop. However, the pH of the digestive tract from the proventriculus to the distal small intestine is unaffected.