Effect of Tall Fescue Toxins on Stallions and ColtsBy Kentucky Equine Research Staff · March 5, 2012
Tall fescue infected with an endophyte sometimes causes reproductive problems in mares. The effects of endophyte-infected fescue on male horses seems to be less well known.
In a study conducted at the University of Georgia to test the effect, if any, of these ergot alkaloid toxins on male horses, six mature stallions were divided into two groups of which one was fed a high-alkaloid feed and the other received a control feed for 70 days. The groups were switched after a washout period so that each horse consumed both diets. After the test periods, semen was collected from each stallion and examined for sperm quality and quantity. Testosterone level and testicular size was also determined for each stallion. Treated stallions tended to produce a smaller volume of ejaculate, but no negative effects were noted on sperm quantity or characteristics.
When yearling colts were given the same treatment, however, an effect was noticed. In about a third of the colts given ergot alkaloid toxins, abnormalities in chromosome pairings during cell division were seen. It is not known whether this abnormality would have any effect on breeding potential when the colts became mature.