Ruminal Changes during the Onset and Recovery of Induced Lactic Acidosis in Sheep

Four crossbred wethers equipped with rumen fistulas were used to study changes in rumen pH, motility and the synthesis of volatile fatty acids and lactic acid during the onset and recovery of induced lactic acidosis. Acidosis was induced by the addition of sucrose (15 g/kg BW) in 700 ml of water through the fistula. Mean maximum lactic acid concentration was near or in excess of 100 mM of rumen fluid during the first 48 hr postinducement. The minimum pH values observed for each sheep were 4.53, 4.13, 4.29 and 4.48. Propionic and butyric acids were absent from rumen samples by 14 hr postinducement. Acetic acid concentrations decreased to < 5 mM during the first 24 hr following the addition of the sugar. Rumen motility decreased in frequency and amplitude during the first 4 hours. Normal rumen motility was observed in one sheep by 52 hr but not in another, until 84 hr postinducement. Two of the four sheep were “off feed” by 4 postinducement, while the remaining two did not become anorexic until 7 hours. Animals began to consume small amounts of alfalfa when rumen pH values increased to >5.0 but consumption similar to preinducement intake was not observed until the rumen pH was >6.0 and lactic acid could no longer be detected in the rumen fluid.