Relationship of rumen gram-negative bacteria and free endotoxin to lactic acidosis in cattle.

Feeding grain to animals not adapted to grain resulted in a marked increase in the . / . concentration of free endotoxln m the rumen. Endotoxin concentration increased 15 to 18 times within 12 hr after lactic acidosis was induced through grain engorgement. The increase was accompanied by a shift from predominantly gram-negative to gram-positive bacteria. Data from in vitro fermentations showed that the increase in free endotoxin concentration was not accompanied by a decrease in the number of gram-negative bacteria. The absorption of endotoxin from the rumen was not apparent by the actinomycin D assay procedure because no difference was observed in mice lethality of plasma from control and post-engorgement samples. However, the significant granulocytosis that accompanied acidosis was suggestive of systemic action of rumen bacterial endotoxin. (