The October 2009 Healthy Animals Newsletter from the Agricultural Research Service (ARS) says new research is shedding light on the relationship between chemical compounds and fescue toxicosis—a disease that affects grazing animals and costs the U.S. cattle industry an estimated $600 million annually.

Tall fescue can cause toxicosis in cattle and other ruminants if it's infected with endophytic fungus, causing lameness and reduced production efficiency, and can even be fatal if infected animals are subjected to stressful situations, such as extreme heat or long-distance transport.

Scientists believe many symptoms of toxicosis are caused by chemical compounds known as ergot alkaloids, but much is still unknown about how they cause clinical signs to develop.

One sign of toxicosis is a narrowing of blood vessels. Research is showing that of the three alkaloids tested, ergovaline was the most effective at making the veins contract. The others, N-acetylloline and lysergic acid, had little effect. Combining two alkaloids did not increase the toxicity of either—at least in terms of vein contraction. Further research is underway to determine how these alkaloids influence other tissues, organs and physiological systems.

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