Endotoxin and arachidonic acid metabolites in portal, hepatic and arterial blood of cattle with acute ruminal acidosis.

Ruminal acidosis was induced experimentally with 70 g barley/kg body weight in 2 rumen fistulated cows with chronic indwelling catheters in the portal vein, in a hepatic vein and the carotid artery. The cows were followed for 24 and 20h after the overfeeding and evaluated clinically and by clinical chemistry. The 2 cows exerted different responses to the treatment. Both cows showed signs of severe ruminal acidosis. Both cows had endotoxin in portal and hepatic vein blood, but only 1 of the cows convincingly developed a systemic endotoxaemia. A pre-hepatic release of the stable prostacyclin and thromboxane metabolites, 6-ketoprostaglandin F1 alpha and thromboxane B2 was demonstrated in this cow. The results of the present study show that endotoxin and arachidonic acid metabolites of pre-hepatic origin may be factors involved in the pathogenesis of ruminal acidosis, and that investigation of the factors affecting translocation of ruminal endotoxin and subsequent clearing in the liver, will be of importance.