Electrolyte diets, stress, and acid-base balance in broiler chickens

We compared the acid-base balance in broiler chickens provided diets containing 2 dietary electrolyte balances (DEB), and administered with either adrenocorticotropic hormone (ACTH) or saline solution. Diets were moderate (174 mEq/kg) or high (241 mEq/ kg) DEB formulated by altering Na-K-Cl based on actual analysis. The experiment was designed as a split plot, with the main unit consisting of 4 treatments and the factorial treatment structure arranged in a completely randomized design. Osmotic pumps delivered 8 IU of ACTH in saline/kg of BW per d for 7 d, or the same saline volume as used in ACTH at 1 mu L/h for 7 d was implanted on d 35. Venous blood samples were collected on d 35 before the pumps were implanted and on d 42 and 49. Birds fed the high DEB diet exhibited significantly higher Na+ and Ca (2+) levels than birds provided the moderate DEB diet on d 35. Infusion of ACTH significantly increased (P <= 0.05) hematocrit, hemoglobin, partial pressure Of CO2 (pCO(2)), corticosterone, osmolality, and HCO3- and reduced pH, BW, partial pressure of O-2 (pO(2)), and plasma concentrations of Na+ and Cl- in both diets compared with the control group on d 42. Similarly, the ACTH treatment significantly increased hematocrit, hemoglobin, Ca 2+, corticosterone, and osmolality and reduced (P <= 0.05) pO(2), glucose, and BW on d 49. The diet formulated for high DEB partially lowered pCO(2) on d 42. Significant DEB x ACTH interactions were observed for pCO(2) and pO(2) on d 49. However, there was a reduction in pO(2) along with a concomitant increase in erythropoiesis under the ACTH treatment for both diets, compared with the saline control, because of the increased need for O-2 to support gluconeogenic energy production. This adaptive response provided greater numbers of erythrocytes and thus a higher amount of circulating hemoglobin to deliver O-2 for metabolism. The diet formulated for high DEB partially attenuated the adaptive stress condition in broiler chickens.