Pregnancy rates in mares following hysteroscopic or transrectally-guided insemination with low sperm numbers at the utero-tubal papilla.
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abstract
This study was conducted to evaluate two methods for insemination of a low number of sperm in the tip of the uterine horn, and to determine whether prebreeding intrauterine treatment with prostaglandin E(2) would improve pregnancy rates. Estrus was synchronized in 36 fertile Quarter Horse and Thoroughbred broodmares. When a dominant follicle >or=33 mm diameter was present, mares were treated with 2500 units hCG intravenously and were assigned to one of four treatment groups for insemination with five million total sperm in 200 microl extender the next day as follows: (1) Group PGE-HYS (n=9): 0.25mg PGE(2) in 1 ml 0.9% NaCl solution infused into the tip of the uterine horn ipsilateral to the dominant follicle 2h prior to hysteroscopic-guided inseminate placement onto the oviductal papilla; (2) Group SAL-HYS (n=9): 1 ml 0.9% NaCl solution infused into the tip of the uterine horn ipsilateral to the dominant follicle 2h prior to hysteroscopic-guided inseminate placement onto the oviductal papilla; (3) Group PGE-PIP (n=9): 0.25mg PGE(2) in 1 ml 0.9% NaCl solution infused into the tip of the uterine horn ipsilateral to the dominant follicle 2h prior to transrectally-guided pipette placement of the inseminate into the tip of the uterine horn; and (4) Group SAL-PIP (n=9): 1 ml 0.9% NaCl solution infused into the tip of the uterine horn ipsilateral to the dominant follicle 2h prior to transrectally-guided pipette placement of inseminate into the tip of the uterine horn. Mares in estrus were evaluated daily by transrectal ultrasonography to monitor follicular status and confirm ovulation. If mares had not ovulated within 2 days of insemination, the assigned treatment was repeated. Pregnancy status was evaluated by transrectal ultrasonography 12-14 days postovulation, and pregnancy rates were compared. No interaction between prebreeding treatment (SAL:PGE) and insemination protocol (HYS:PIP) on pregnancy rates occurred (P>0.10). Pregnancy rates did not differ between mares inseminated by HYS (12/18; 67%) or PIP (10/18; 56%) (P>0.10). Pregnancy rates did not differ between mares treated prior to breeding with PGE (11/18; 61%) or SAL (11/18; 61%) (P=1.00). In summary, satisfactory pregnancy rates were obtained when a low number of sperm were either placed directly onto the oviductal papilla using hysteroscopy or placed in the tip of the uterine horn using a transrectally-guided uterine pipette. Infusion of 0.25mg PGE(2) in the tip of the uterine horn 2h prior to insemination did not improve pregnancy rates.
