Trans-Aconitate Utilization by Sheep

Abstract

Sheep fed diets con-taining 3.5 and 7.0% trans-aconitate on a dry weight basis for 5 days appeared normal and maintained normal levels of blood citrate, ketones, and aconitate, but showed large increases in urinary citrate. Ca and Mg levels in plasma and urine were not substantially modified. When trans-aconitate was placed in the rumen it disappeared rapidly but did not increase the concentration of rumen volatile fatty acids; blood and urinary aconitate values remained low. trans-Aconltate did not inhibit the fermentation of soluble substrates by rumen microorganisms in vitro. Both cis- and trans-aconitate were fermented slowly. Intravenously injected sodium trans-aconitate at 1.0 m-mole/kg body weight produced no ill effects. The citrate which subsequently accumulated in blood and urine was not a radiometabblite of [1,5-14C]trans-aconl-tate, suggesting that it was formed by aconitate hydratase inhibition. Plasma Ca and Mg values were not depressed by intravenous trans-aconitate administration but urinary Ca excretion increased and urinary Mg decreased. Under similar conditions of injection, sodium citrate was lethal. These data are believed to exclude trans-aconltate as a sole cause of lethal aconitate hydratase inhibition or of hypomagnesaemia in''sheep.