This may cause excessive hemorrhaging, resulting in mare death. Uterine infections may increase, thus causing a delay in rebreeding. If these are not problems enough, mares on fescue may have reduced milk production or no milk at all. Colostrum production may be decreased or nonexistent. Excess dopamine suppresses the production of the reproductive hormone prolactin.
Prolactin is essential to the final stages of pregnancy and birth.
Another contributing factor to prolonged gestation is suppression of the hormone progesterone. Progesterone levels should increase about two weeks before parturition, but mares exposed to endophyte infected fescue have reduced progesterone levels. Growing Horses A grazing study conducted at Auburn University used yearling geldings and fillies to determine if grazing endophyte-infected tall fescue had an adverse effect on the growth and development of young horses. Average daily gain, change in wither height, and rectal temperature were measured. Average daily gain was lower for yearling horses grazing the high infected fescue, but no significant differences were measured for change in wither height or rectal temperature.