Pregnancy rates in mares following hysteroscopic or transrectally-guided insemination with low sperm numbers at the utero-tubal papilla.

The study investigates the effectiveness of two methods of insemination in horses, where a small amount of sperm is delivered directly to the tip of the uterine horn. It also explores if a pre-breeding treatment using Prostaglandin E(2) (PGE(2)) can increase pregnancy rates. Both the insemination methods and PGE(2) treatment showed satisfactory pregnancy outcomes without any significant differences in results.

Research Methods

• The study involved 36 fertile broodmares belonging to Quarter Horse and Thoroughbred breeds. The mares’ estrus was synchronized to align their reproductive cycles.
• When a dominant follicle (a developing egg within the ovary which is ready to be released for fertilization) 33mm or larger was spotted, the mares were given an intravenous dose of 2500 units of hCG (Human Chorionic Gonadotropin, a hormone that stimulates ovulation).
• The mares were then randomly assigned to one of four treatment groups. Each group was treated with a different combination of prebreeding treatments and insemination methods using five million total sperm in 200 microliters of extender.
• Both the insemination methods – hysteroscopic-guided placement into the oviductal papilla and transrectally-guided insertion into the top of the uterine horn – and the pre-breeding treatments (with PGE(2) or SAL(0.9% NaCl solution)) were evaluated for effectiveness.
• Follow-ups were conducted using transrectal ultrasonography in order to monitor follicular status, confirm ovulation, and verify pregnancy status 12-14 days after ovulation.

Results

• The results showed no significant difference in pregnancy rates between the mares that were inseminated using hysteroscopic-guided placement (67%) and those using transrectally-guided insertion (56%) methods.
• Also, the pre-breeding treatment (either PGE or SAL) did not significantly affect the pregnancy rates, with both methods yielding a 61% pregnancy rate.
• Furthermore, the same direct insemination technique with or without prebreeding infusion of 0.25mg PGE(2) in the tip of the uterine horn 2 hours prior to insemination, did not significantly affect pregnancy rates.

Conclusion

• The study concluded that both insemination methods – placing sperm directly onto the oviductal papilla using hysteroscopy or placing sperm in the tip of the uterine horn using a transrectally-guided uterine pipette – yielded satisfactory pregnancy outcomes.
• The prebreeding intrauterine treatment with PGE(2) did not significantly improve pregnancy rates. This indicates that the use of PGE(2) as a prebreeding treatment may not be necessary while using these insemination techniques.