Fescue's nasty little sidekick is one step closer to being exposed, say researchers in Kentucky.
The symbiotic relationship between fescue and its endophyte remains a complex and only partially understood problem for fully one-fifth of the nation's cattle producers. But USDA's Ag Research Service this week announced its cooperative work with the University of Kentucky may have isolated the most-responsible toxin produced by the fescue endophyte.
Scientists believe many symptoms of toxicosis are caused by chemical compounds known as ergot alkaloids – a form of mycotoxin – and that one of the alkaloids called ergovaline was the most effective at making cattle veins contract. Two others, N-acetylloline and lysergic acid, had little effect on vein contraction.
The results also showed that combining two alkaloids did not increase the toxicity of either--at least in terms of vein contraction.
Yet little is known about how they cause clinical signs to develop.
The researchers are also studying how these alkaloids influence other tissues, organs and physiological systems.
In one study, the scientists showed that ergovaline, but not lysergic acid, can bioaccumulate in vitro, suggesting that ergovaline may be more likely to induce toxicosis.
The scientists say this type of research is essential for understanding how endophyte-infected tall fescue influences grazing animals.
They believe eventually it could help determine which specific compounds are most toxic and how to protect cattle from them. A variety of possible solutions to this problem are being researched. Among them:
Several sources continue seeking compounds which might effectively provide an "antidote" or counterbalancing agent for the toxins.
In a 1994 Georgia study, researchers found active immunization of yearling Angus heifers with immunogens containing lysergol or ergonovine linked to human serum albumin resulted in an antibody response.
Other work is searching the bovine genome for a genetic marker to correlate with resistance to the fescue endophyte.