Tall fescue is the predominant grass used for grazing in the United States. But more than 80% of the tall fescue in the "Fescue Belt" region is infected with an endophytic fungus. Once consumed, the fungus produces ergot alkaloid toxins that cause fescue toxicity in grazing animals, costing the livestock industry nearly $1 billion annually in lost production. Scientists at the Agricultural Research Service are now using Doppler technology - the very same used by meteorologists to track thunderstorms - to better understand the rate at which fescue toxicity restricts blood flow in cattle.
Using the Doppler technology, scientists found that blood flow decreases within 24 hours of feeding cattle ergot alkaloids. Results show that in cattle consuming diets containing ergot alkaloids, blood flow through the caudal artery, which supplies blood to the tail, can be reduced by as much as 50% compared to cattle on alkaloid-free diets. Constricted blood flow to peripheral tissues reduces the animal's ability to dissipate body heat, making it vulnerable to heat stress.
The research has helped scientists better understand ergot alkaloids and the mechanisms by which they cause toxicity. This knowledge could lead to improved forage and animal-management protocols that decrease exposure or enhance tolerance to the alkaloids of endophyte-infected tall fescue.