Frozen semen has several distinct advantages over fresh and cooled semen.
The primary disadvantages of frozen semen in an equine breeding program are stallion variability in response to freezing, cost to collect, freeze and store semen, intensified mare management, and slightly lower pregnancy rates per cycle.
Sperm from some stallions do not tolerate freezing and thawing. Consequently, post – thaw motility and pregnancy rates can vary greatly between stallions. Performing a 'test freeze' is very valuable in determining if semen from a stallion can be frozen successfully and which freezing extender is most suitable for each stallion. A minimum of 30% progressive motility should be present post-thaw for a stallion to be considered a 'good freezer'. Proper storage and handling of frozen semen is critical for future success.
The number of straws required for a breeding dose is dependent on the total number of sperm in the straw and the insemination technique. The mare is examined 3 to 4 times per day as ovulation approaches and the mare is inseminated immediately after ovulation is detected.
Prediction of ovulation and timing of insemination with frozen semen is facilitated by administration of ovulation-inducing agents, like deslorelin. Typically, a mare in oestrus would be given one of these agents once a follicle larger than 35mm in diameter is detected. In most instances, ovulation will occur in 36 to 40 hours after deslorelin administration.
Average pregnancy rates per cycle for mares bred with frozen semen are 30 to 40%. Some stallions may have per cycle pregnancy rates of 50 to 70% using frozen semen, while frozen semen from other stallions will be unsuccessful in getting mares in foal. In general, pregnancy rates per cycle using frozen semen are 5 to 10% lower than with cooled-transported semen.
Management of mares for breeding with frozen semen may seem intimidating. However, by following a few simple guidelines, frozen semen can be used very successfully in a breeding program.
We are a well-established equine practice servicing South Auckland and the greater Auckland area. With our purpose-built hospital and surgical facilities our experienced staff are able to provide quality care with a full range of medical, diagnostic and surgical services.
