Effect of intrauterine treatment with prostaglandin E-2 prior to insemination of mares in the uterine horn or body

Two trials were conducted to investigate the effects of intrauterine infusi on of PGE(2) and uterine horn insemination on pregnancy rates in mares achi eved by breeding with a suboptimal number of normal spermatozoa. Estrus was synchronized and mares were teased daily with a stallion to detect estrus. Mares in estrus were examined by transrectal palpation and ultrasonography to monitor follicular status. On the first day a 35-mm diameter follicle w as present, hCG (1500 TU, iv) was administered and the mares were bred the next day. Mares (Trial 1, n = 34; Trial 2, n = 28) were inseminated with 25 million total spermatozoa from either a stallion with good semen quality ( Trial 1) or poor semen quality (Trial 2). In each trial, mares were assigne d to 1 of 4 treatment groups as follows: Group PGE-HI - infusion of 0.25 mg PGE(2) into the proximal end of the uterine horn ipsilateral to the domina nt follicle 2 h prior to insemination in the proximal end of the same uteri ne hem; Group PGE-BI - infusion of 0.25 mg PGE2 into the proximal end of th e uterine horn ipsilateral to the dominant follicle 3 h prior to inseminati on in the uterine body; Group SAL-HI - infusion of 1 mt sterile saline into the proximal end of the uterine horn ipsilateral to the dominant follicle 2 h prior to insemination in the proximal end of the same uterine hem; or G roup SAL-BI - infusion of 1 mt sterile saline into the proximal end of the uterine horn ipsilateral to the dominant follicle 2 h prior to insemination in the uterine body. After breeding, mares were examined daily by transrec tal ultrasonography to confirm ovulation, and were re-examined 14 to 16 d a fter ovulation for pregnancy status. Data were analyzed by Chi-square.