A team of University of Kentucky (UK) researchers recently evaluated whether horses consuming endophytic alkaloids experienced vasoconstriction (narrowing of the blood vessels), a phenomenon previously reported in cattle. As pard of the study, researchers also tested a method by which to detect the condition.

Tall fescue is a cool-season perennial grass prominent in the eastern portions of the United States that can be infected with an endophytic fungus known to produce chemicals called alkaloids.

“It is the alkaloid chemicals that have the detrimental health effects on cattle and horses, and it is the alkaloids such as ergovaline that we are interested in,” explained study author Karen McDowell, MS, PhD, a reproductive biology specialist at UK’s Gluck Equine Research Center.

These alkaloids, when consumed by mares in late pregnancy, can cause dystocia (difficult birth), thickened placenta, and reduced milk production. Previous studies have shown that endophyte alkaloid consumption causes vasoconstriction in cattle, but this phenomenon had not been examined in horses. To that end, the research team tested the hypothesis that if horses consumed fescue seed containing the endophytes, the horses would experience vasoconstriction measurable by Doppler ultrasonography. Doppler ultrasonography illustrates velocity (speed) and direction of blood flow, and during vasoconstriction, both are negatively affected.

The team employed 11 horses housed in drylots and randomly assigned them to one of three fescue seed treatments: ground endophyte-free seed (E-G), whole endophyte-infected seed (E+W), or ground endophyte-infected seed (E+G).