North American Veterinary Licensing Examination (NAVLE) Practice Test

Fescue toxicity is indeed the primary factor contributing to agalactia in mares that are grazing on fescue grass contaminated with Acremonium coenophialum. This specific type of fescue, often referred to as endophyte-infected fescue, contains alkaloids that can have various physiological effects on pregnant mares. The most significant of these effects is the alteration of normal hormonal balances during late gestation, particularly the production of prolactin, which is a key hormone involved in milk production.

When mares consume this contaminated fescue, the ergovaline and other alkaloids present can inhibit prolactin release, leading to a lack of mammary gland development and subsequent failure to produce milk, known as agalactia. This presents significant risks not only to the mare but also to the foal, who depends on colostrum and milk for adequate nutrition and immunity shortly after birth.

While factors like mastitis, malnutrition, and placentitis can affect milk production, they do not directly relate to the specific pathophysiology caused by the alkaloids in endophyte-infected fescue. Therefore, fescue toxicity is the most appropriate and direct cause of ag