Pregnancy outcomes using stallion epididymal sperm stored at 5 °C for 24 or 48 hours before harvest.

The research focuses on the success rates of pregnancies in mares after being inseminated with epididymal sperm that has been stored and cooled at 5°C for either 24 or 48 hours prior to sperm harvest and cryopreservation. It aims to replicate previous studies that achieved a 60% success rate with 24-hour storage before harvest and to investigate if similar results could be obtained with a 48-hour storage period.

Purpose of the Research

The primary goal of this research was to:

• Replicate an approximately 60% one-cycle pregnancy rate using epididymal sperm cooled and stored within the epididymis for 24 hours before harvest and cryopreservation, results which had been previously obtained in other studies.
• Evaluate the pregnancy outcome using epididymal sperm that has been cooled and stored within the epididymis for 48 hours prior to sperm harvest and cryopreservation – a new area of study.

Procedure of the Experiment

Testicles were obtained from 13 stallions that had been castrated as part of a routine procedure. The epididymides were cooled and stored at 5 °C for either 24 or 48 hours prior to the sperm harvest and cryopreservation. The freezing extender used in the cryopreservation was based on egg yolk and dimethylformamide.

Experiment Setup and Results

On one cycle, 13 mares were inseminated with the cryopreserved epididymal sperm that was stored for 24 hours before the harvest. Out of the initial group of 13 mares, 10 mares were then also inseminated in a previous or subsequent cycle with samples from the same stallion that had been stored for 48 hours before harvest.

The study found that:

• 7 out of the 13 inseminations resulted in pregnancy when using sperm stored for 24 hours before harvest. This result agrees with the previous success rate found in other studies.
• 4 out of the 10 inseminations resulted in pregnancy when using sperm stored for 48 hours before harvest. This demonstrated that successful pregnancies can still be achieved even when the epididymides are stored and cooled for 48 hours before the harvest and cryopreservation of sperm.

The study effectively provides useful insight into the potential of epididymal sperm usage within breeding practices, extending the viability of sperm storage up to a 48-hour timeframe while still maintaining successful pregnancy outcomes.