Influence of endometrial cysts on conception rate of mares.

A total of 259 normally fertile mares were examined gynecologically by means of rectal palpation and ultrasonography in order to record the presence of uterine cysts and pregnancy. The incidence of endometrial cysts was 22.4%. Of the 95 cysts observed during the trial, 87.4% were located in the middle and posterior segments of both uterine horns. The size of all endometrial cysts ranged between 3 and 48 mm. When all mares were assigned to three age groups, A < 7 years (n = 116), B 7-14 years (n = 117) and C > 14 years (n = 26), a significant (P < 0.01) increase in the number of endometrial cysts was observed with advancing age (4.3%, 29.1% and 73.1%, respectively). The pregnancy rates at Days 14 and 40 were significantly (P < 0.01) lower in mares with cysts (77.6% and 71.4%) compared to mares without cysts (91.5% and 88.0%). This suggests that the presence of uterine cysts plays an important role in the reduction of fertility of Thoroughbred mares.