Endotoxemia in Dairy Cattle: Role of Eicosanoids in Reticulorumen Stasis

¹ Departments of Large Animal Medicine and Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens 30602

The role of arachidonic acid metabolites in the forestomach stasis induced by Escherichia coli endotoxin was evaluated. Six adult Holstein cows received saline solution; endotoxin at 1, 10, and 100 ng/kg of body weight; flunixin meglumine at 1.1 mg/kg of body weight; and flunixin meglumine at 1.1 mg/kg plus endotoxin at 100 ng/kg. The fre- quency of reticulorumen contractions, mental attitude, body temperature, respiratory rate, heart rate, and plasma concentration of prostaglandin E₂. prostacyclin, and thromboxane were evaluated. Administration of saline solution and endotoxin at 1 ng/kg had no significant effects. Administration of endotoxin at 10 ng/kg did not cause significant clinical effects or alter reticulorumen contractions but enhanced synthesis of thromboxane. Administration of en- dotoxin at 100 ng/kg caused mild clinical signs of stasis, reduced the frequency of reticulorumen contractions, and enhanced synthesis of thromboxane and prostacyclin. Reticulorumen stasis was not accompanied by an increase in the plasma concentration of prostaglandin E². Flunixin meglumine abolished endotoxin-induced reticulorumen stasis, tachycardia, and synthesis of arachidonic acid metabolites. Reticulorumen stasis during bovine endotoxemia is caused either by enhanced synthesis of an arachi- donic acid metabolite other than prostaglandin E₂ or by local synthesis of prostaglandin E₂.

Key Words: endotoxemia • rumen • eicosanoids • stasis

Submitted on March 16, 1992
Accepted on September 17, 1992

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