DIETARY ELECTROLYTE BALANCE EFFECTS ON PERFORMANCE AND METABOLIC CHARACTERISTICS IN FINISHING STEERS

One hundred twenty Angus and Angus-Hereford crossbred steers (337 +/- 3 kg) were used in a randomized complete block design to evaluate the effects of dietary electrolyte balance (DEB; Na + K - Cl) on performan ce, acid-base status, and plasma mineral concentrations in cattle cons uming a high-concentrate, low-fiber (5% cottonseed hull) diet. The ste ers were blocked into six groups based on BW and pen location, with fi ve steers per pen. The treatments consisted of 0, 15, 30, and 45 mEq o f DEB/ 100 g of DM. Average daily DMI increased linearly (P < .01) wit h increasing DEB for the first 28 d then increased quadratically (P < .05) for the remainder of the study. Daily gain tended (P < .10) to in crease quadratically, whereas gain:feed was not affected by DEB. Carca ss marbling score increased quadratically (P < .05), but other carcass measurements were not affected by DEB. On d 42, arterial blood pH was increased quadratically (P < .10) and HCO3 responded cubically (P < . 10) to DEB, whereas ionized Ca, pCO(2), and pO(2) were not affected by treatment. On d 84, pCO(2)(P < .10) and HCO3 (P < .05) decreased line arly as DEB increased. On d 42, plasma concentrations of Na, K (P < .1 0), and Mg (P < .05) decreased quadratically with increasing DEB. Plas ma Cl concentrations decreased linearly (P < .05) with increasing DEB on d 42. On d 84, total plasma Ca increased linearly (P < .10) with in creasing DEB. Plasma Na, K, Mg, and Cl were not affected on d 84. Thes e data indicate that gain and feed intake by finishing cattle were max imized with a diet that contained a DEB of 15 mEq/100 g of DM.