In many states, the main cause of this type of problem is endophyte (fungus)-infected fescue. However, you should contact your veterinarian to examine the dead foals for any sign of infection or other problems. If no infectious problem is found, then it could be caused by endophyte-infected fescue. Contact your local Cooperative Extension office for assistance in identifying fescue and testing your pasture. If your mares are on native fescue, assume that it is endophyte-infected and remove the mares from this pasture. The endophytes in the fescue cause a wide array of reproductive problems including stillbirths, foaling difficulty, poor milk production in the mare, and large but immature foals. If you do not have access to a pasture without endophyte-infected fescue, you may have to confine the mares in stalls or a drylot until 30 days after foaling. It is recommended that you keep the mares off endophyte-infected fescue a minimum of 30 days before and after foaling, but 90 days before and after foaling is a safer time frame.