Absorption of tricarballylic acid from the rumen of sheep and cattle fed forages containing trans-aconitic acid

Some forages accumulate high concentrations (<5% of dry matter) of trans-aconitate, and this acid has been implicated in Mg chelation and the occurrence of grass tetany in ruminants. In vitro experiments have indi- cated that rumen microorganisms convert trans-aconitate to tricarballyl- ate. The feeding studies described here were conducted to demonstrate absorption of tricarballylate by ruminant animals fed diets similar to those producing grass tetany. When sheep were switched from a diet containing alfalfa (lucerne) (Medicago sativa L.) hay (no detectable trans-aconitate) to wheat (Triticum aestivum L.) and rye (Secale cereale L.) forage containing 1 .52 and 1 .37% trans-aconitate, respectively, there was a rapid increase in blood plasma tricarballylate. Trans-aconitate was not detected in the plasma. At 16 h after feeding, plasma tricarballylate concentrations were 0-58±0 .08 and 0 .48±0 .21 mm in sheep fed the wheat and rye forage, respectively. Tricarballylate concentrations remained relatively constant for the remaining 60 h of the experiment. Cattle were fed rye forage one week later, and the concentration of trans-aconitate in the forage had dropped to 0 .83% of the dry matter. Once again there was a rapid