Effect of thiopeptin and sodium bicarbonate on the prevention of lactic acidosis induced in sheep.

Four crossbred wethers were utilized in a randomized block design to test Thiopeptin, an antibiotic, at .25% of the amount of wheat given, two levels of NaHCO3 (2 and 4%) expressed as a percentage of the wheat given, and a combination of the Thiopeptin (.25%) plus 2% NaHCO3. Acidosis was induced in the four sheep (controls) by feeding cracked soft white wheat at 50 g/kgBW -Ts divided among three feedings given over an 8-hr period on the third day of the experiment. Additional wheat was given depending on rumen pH values at 0800 of the fourth day. All control sheep received wheat until rumen pH was below 4.5. Ruminal pH, rumen lactic and volatile fatty acid levels in rumen fluid were monitored four times daily for 96 hr postengorgement. The 2 and 4% NaHCO3 and the antibiotic plus 2% NaHCO3 treatments were all effective in maintaining a higher pH than the control treatment (P<.01) and these treatments maintained a higher pH than the antibiotic by itself (P<.05). Low concentrations of rumen lactic acid (< 30 mM) were detected on the antibiotic treatment. All treatments were effective in preventing acute acidosis and none of the animals went off feed. The 4% NaHCO3 treatment resulted in higher (P<.05) acetic acid concentrations than the treatments containing Thiopeptin. Treatments containing Thiopeptin resulted in increases in propionic acid (P<.01) and reduced acetic to propionic ratios corn-