Clinical Findings before and after the Removal of Ovaries Affected with Granulosa Theca Cell Tumor (GTCT) in 16 Mares

To clarify the clinical findings in mares with granulosa theca cell tumor (GTCT) and to determine reproductive activity after surgery, 16 mares with GTCT were studied. The GTCTs were found in 10.4 ± 0.9 year olds. The clinical signs manifested by the affected animals varied, and the mares showed abnormal behavior, that is, anestrus (n=5), continuous estrus (n=8) and stallion-like behavior (n=3), but most of the affected mares (11/16) were sterile for long periods (1-4 years), and in four animals GTCTs were detected at the post-partum period. In 11 of the 16 animals, the ovary containing tumor was enlarged on the right side, whereas the contralateral ovary was atrophied in all the 16 animals. Mares in which the affected ovary was surgically removed in the non-breeding season (n=8) had estrus 2.6 months earlier and became pregnant 2.9 months earlier than those operated on (n=8) in the breeding season, by resuming the reproductive function in the remaining ovary. All three mares that died from hemorrhage after the surgery were operated on in the breeding season. From these results we confirmed that GTCT is related to sterility for long periods in mares and that surgical removal of the affected ovary is effective in restoring reproductive function. And it is also suggested that the affected ovary should be removed in the non-breeding season.