Fescue-Related Toxicosis
Basic Information 
Epidemiology
Risk Factors
• Generally subacute to chronic consumption of endophyte-infected fescue in pastures or hay
• Late-gestational mares (~270–300 days)
• Mares in the spring transitional phase before the onset of normal cyclicity
• Endophyte-infected fescue in the seed head stage
• Aberrant weather conditions (eg, flood, drought) that favor growth of endophyte-infected fescue
• High rate of application of nitrogen-containing fertilizers
• Concurrent exposure to Claviceps purpurea ergot in pastures, hay, grain, and especially pelletized rations incorporating “screenings” (see “Ergot-Related Toxicosis” in this section)
Geography and Seasonality
• Upper Southeastern and lower Midwestern United States; the area of distribution is increasing in size
• Worldwide distribution in parts of South America, Europe, Africa, and Asia
• Spring when mares are cycling and being bred and when foals are being born
• Seasonal variation in toxin concentration occurs, with the riskiest time of year being late spring when the grass is in the seed head stage.
Clinical Presentation
History, Chief Complaint
• Agalactia or dysgalactia may be observed in the absence of any other clinical signs.
• Dystocia or premature placental separation (ie, “red bag”)
• Fetal dysmaturity or overmaturity
• Prolonged transitional phase before the first ovulation or abnormal cyclicity in the spring
• Conception failure or early embryonic loss
• Impaired athletic performance in hot weather
• See “Ergot-Related Toxicosis” in this section for other hyperthermic and gangrenous effects (uncommon in horses).
Physical Exam Findings
• Little or no udder development within 14 days of the due date; this may be the only clinical sign seen
• Dystocia with an abnormally large or malpositioned foal
• Premature separation of the chorioallantois (“red bag” presentation)
• Thickened, edematous fetal membranes, possibly retained
• Dysmature or overmature foal unable to suckle
• Multiple, anovulatory follicles; failure to ovulate in a timely fashion
• Increased sweating and heat intolerance during exercise in hot weather
• Multiple limb lameness or laminitis
• See “Ergot-Related Toxicosis” in this section for other hyperthermic and gangrenous effects (uncommon in horses).
Etiology and Pathophysiology
• Fescue toxins consist of a number of ergopeptine alkaloids, including ergovaline (the ergopeptine of highest concentration), and ergoline alkaloids, including lysergic acid.
• In mares, these toxins cause the following:
< div class='tao-gold-member'>
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
