Fertility of mares after unilateral laparoscopic tubal ligation.
OBJECTIVE: To develop a technique for laparoscopic tubal (oviductal) ligation and to evaluate pregnancy rates for mares that ovulated ipsilateral or contralateral to the ligated oviduct. STUDY DESIGN: Randomized prospective clinical trial comparing pregnancy rates after unilateral laparoscopic tubal ligation. ANIMALS: Twelve mares of light horse breeds. METHODS: One oviduct in each of 6 mares was surgically ligated with a laparoscopic technique; 6 other mares served as nonligated controls. Mares with unilateral tubal ligations (UTL) were inseminated with 500 million progressively motile sperm during 1 cycle when the dominant follicle was ipsilateral to the ligation site and 1 cycle when the dominant follicle was contralateral to the ligation site. Control mares were bred during 2 cycles regardless of the side of the dominant follicle. Pregnancy examinations were performed on days 12, 14, and 16 after ovulation by transrectal ultrasonography. RESULTS: None of the mares became pregnant when ovulations occurred from the ovary adjacent to the ligated oviduct. All 6 mares became pregnant on the first cycle when an ovulation occurred from the opposite ovary. Control mares became pregnant on 10 of 12 cycles (83.3 %). CONCLUSIONS: UTL was completely effective in preventing pregnancy when ovulation occurred ipsilateral to the ligation site. The surgical procedure did not interfere with the establishment of pregnancy when ovulation occurred from the contralateral ovary. CLINICAL RELEVANCE: UTL may be a clinically useful procedure for preparing a recipient mare for gamete intrafallopian transfer. The recipient mare could be allowed to ovulate and UTL would prevent fertilization of her oocyte but would not interfere with normal corpus luteum formation. The donor oocyte could be placed into the oviduct contralateral to the UTL site.