Equine fescue toxicosis: signs and solutions.

The research article discusses the negative impact of a toxic grass called endophyte-infested (E+) tall fescue on pregnant horses and their foals, as well as possible solutions to counteract these effects.

Signs and Symptoms of Equine Fescue Toxicosis

• The research found that when pregnant mares graze on fields of E+ tall fescue, they exhibit a variety of adverse health symptoms. These include an extended gestation period, lack of milk (agalactia), high mortality rates in both mares and foals, excessively rough and thick placentas, and the birth of weak and slow-to-develop (dysmature) foals.
• Horses grazing on E+ tall fescue exhibited increased sweating, decreased levels of serum prolactin and progesterone, and an increase in serum estradiol-17 beta levels.
• Interestingly, unlike many other species, horses consuming E+ tall fescue do not exhibit an elevated body temperature.

Effects of E+ Tall Fescue Hay on Digestibility and Growth

• The study also pinpointed that E+ tall fescue hay is not as efficiently digested by horses as endophyte-free (E-) hay.
• Young horses solely consuming E+ pasture had worse weight gain compared to counterparts consuming E- pasture. However, when the pasture was supplemented with additional nutrient concentrates meeting the NRC’s requirements for growth, there was little difference in weight gain.

Ineffective Solutions and Potential Causes

• Attempts to mitigate the effects of toxic tall fescue on the reproduction and milk production of pregnant mares using selenium injections or supplementing with corn were unsuccessful.
• The adverse symptoms are suspected to arise from the alkaloids present in E+ tall fescue acting as D2 dopamine receptor agonists, which would explain their effect in lowering prolactin.

Potential Solution for Equine Fescue Toxicosis

• The research found that Domperidone, a dopamine receptor antagonist, is effective in preventing the signs of tall fescue toxicosis in horses without causing side effects commonly associated with drugs that affect the central nervous system (neuroleptic side effects).