Environmental endocrine-disrupting chemicals can affect horse reproductive health and development, with fescue toxicosis being the most significant practical welfare concern.
Endocrine disruption welfare in horses is most concretely expressed through fescue toxicosis: mares grazing endophyte-infected tall fescue in late pregnancy produce no milk, have prolonged gestation, and experience difficult deliveries. The foal cannot survive without colostrum, meaning fescue toxicosis directly causes preventable neonatal death. This represents severe welfare harm for both mare and foal that is entirely preventable through pasture management. Phytoestrogen effects are typically more subtle, causing irregular cycles and reduced conception rates, representing welfare concerns for breeding mares and economic concerns for operations.