What is fescue toxicosis and which cattle breeds are most susceptible?

Fescue toxicosis is heat stress and reduced gain caused by an endophyte fungus in tall fescue (Kentucky 31). Symptoms include rough hair coat, low gains, retained winter hair into summer, and reduced reproductive performance. European breeds (Angus, Hereford) are more affected than Brahman-influenced breeds. Solutions: convert to novel-endophyte fescue, dilute with clover and other forages, or shift to Bos indicus genetics.