EFFECTS OF DIETARY CATION-ANION BALANCE ON ACID-BASE-BALANCE AND BLOOD PARAMETERS IN ANAEROBICALLY EXERCISED HORSES

Four mature geldings were used in a 4X4 Latin square experiment design ed to study the effect of dietary cation-anion balance (DCAB), calcula ted as meq (Na+K)-(Cl+S)/kg of diet DM, on urine pH, arterial (A) and venous (V) blood pH, blood gases, blood lactic acid concentration (LA) and recovery heart rates (HR) in horses performing anaerobic work. Di ets consisted of a pelleted concentrate of com, soybean meal and cotto nseed hulls fed at a 60:40 ratio with native prairie grass hay. The fo ur treatments were formed by supplementing the base concentrate with c alcium chloride, ammonium chloride, sodium bicarbonate or potassium ci trate to provide treatment cation-anion balances of 10(Low (L)) 95(Med ium Low (ML)), 165(Medium High (MH)) and 295(High (H)). On the last da y of each 15 day experimental period, horses performed a standard exer cise test (SET) within 4 hrs of the morning feeding. The SET consisted of a 1.64 km sprint at speeds sufficient to elicit heart rates (HR) b etween 200 and 210 beats per minute (BPM). Seventy-two hours prior to the SET, total urine collections for determination of pH were taken ev ery four hours. Arterial (A) and Venous (V) blood samples were taken v ia indwelling catheters pre-exercise (P), immediately after exercise ( 0), and at 1, 2, 3, 4, 5, 10, 30, and 60 minutes of recovery. Urine an d blood pH and blood bicarbonate concentrations increased significantl y with increasing DCAB. Horses consuming the most highly cationic diet s had improved performance (p <.05) and quicker recovery of HR, even t hough blood LA concentrations were elevated. Results from this trial f urther demonstrate that horses ingesting highly anionic diets undergo a nutritionally induced metabolic acidosis. Moreover, when exercised w ithin 4 hours of feeding, horses consuming highly cationic diets achie ved greater work output and recovered more quickly due to the bufferin g effect of the diet.