A chilly conception.

The cool market for stallion semen starts warming up.

An article by Clare Illingworth, SPARK writer, University of Guelph.


After years of giving the cold shoulder to frozen stallion semen because of low fertility rates, the equine industry is now warming up to the idea. It seems the infinite shelf life of frozen semen — coupled with a better understanding of how to best preserve fertility during the freeze-thaw process — could mean an end to its chilly reception.

For nearly a decade, University of Guelph animal science professor Mary Buhr and a team of graduate students have been analyzing aspects of freezing, thawing and artificial insemination (AI) techniques geared towards semen fertility.
“It’s important that we understand what factors affect fertility in semen and where improvements are needed,” says Buhr. “Now, we’re creating a method to freeze and thaw equine semen that allows for the highest fertility.”

Currently, the equine AI industry uses frozen semen in only 10 per cent of breeding attempts. That’s because the frozen semen results in pregnancy only 45 per cent of the time, compared with 70-per-cent success using fresh semen.
But Buhr says fresh semen has many drawbacks. It must be used within four days, and its success-ful use depends greatly on the mare’s reproductive cycle.

In addition, stallions with the most sought-after genes are also the ones that are most successful in competitions. Collecting semen from a competition stallion every other day can be distracting for the horse. That problem wouldn’t arise if the semen were frozen and placed in a sperm bank.

Frozen semen’s infinite storage means breeders will have access to stallions world-wide, allowing the best stallions to sire a larger foal crop with desirable performance traits. Semen can also be banked from aging stallions and rare breeds, preserving these genetics for future use.

This research has been sponsored by the Natural Sciences and Engineering Research Council, the Ontario Ministry of Agriculture and Food, Dynasty Trust and the E.P. Taylor Equine Research Fund.
Is this the missing link?
Guelph researchers' discovery of a natural protein in horse semen — a protein that may disappear when samples are prepared for freezing in liquid nitrogen — could be the missing link in frozen semen fertility, making it a more viable option for horse reproduction.

The protein is called prosaposin, and it’s previously been discovered in the semen of roosters and bulls. Now, University of Guelph animal scientist Mary Buhr and graduate student Debbie Ottier are focusing on it after Ottier discovered it’s also present in stallions.

Prosaposin produces up to a 40-per-cent increase in artificial insemination conception rates when it’s added to stored bovine and avian sperm. Researchers believe it’s possible that the first sperm ejaculated are attached to prosaposin and progress to the egg for fertlization. The subsequent sperm, attached to the remaining proteins,are attacked by the mare ’s defence system, acting almost as decoys for the advancing prosaposin sperm.

Prosaposin may not be present in frozen-thawed sperm. The researchers think its absence could be the cause of the lowered fertility. “The freeze-thaw process could be knocking off prosaposin or other important compounds, and if we replace it in the extender,it ’s hoped we can enhance equine fertility,” Ottier says.