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Freezing semen at the ERL
Equine Semen Freezing

The Equine Reproduction Laboratory (ERL) provides a commercial equine semen freezing and storage service. The objective of this service is to provide horse owners and veterinarians with the latest research and technology available for preserving and storing equine semen.

Semen collection, evaluation, preservation (freezing) and long-term storage of frozen semen is performed at the ERL. The stallion's semen is frozen using different semen-freezing techniques and extenders in order to determine the optimal method of freezing semen for each individual stallion. Aliquots of the semen frozen during the test freeze are thawed and evaluated for their response to the freezing procedure. Currently, semen frozen at the Equine Reproduction Laboratory is packaged in 0.5-ml straws, with eight straws (800 million sperm cells) representing one insemination dose. Although there is tremendous variability between stallions, a typical ejaculate from a stallion will provide approximately eight insemination doses (approximately 64 straws).

Once the optimal freezing protocol is identified, subsequent ejaculates from the stallion are frozen using the optimal procedure. Once the semen is frozen, it can be stored at the ERL indefinitely (see cost structures listed on contract) or it can be transferred to another appropriate storage facility. Unless otherwise directed, all semen that is frozen is stored at the ERL.

In addition to our normal procedure for freeze banking sperm we also can refreeze sperm from an already existing frozen semen straw. Traditional frozen semen that is of limited or poor quality is in higher demand for assisted reproductive techniques such as Intracytoplasmic Sperm Injection (ICSI). In order to maximize the use of a single straw, thawing and evaluating the original straw and subsequently refreezing the sperm at a lower concentration for future use, is possible. Thawing and refreezing sperm can result in sufficient motile sperm per straw for ICSI use. Sperm injection from refrozen sperm has resulted in embryo production and pregnancies. Once refrozen, the semen is only suitable for ICSI use.

2022 General Stallion Services contract

2022 Frozen Semen-Embryo Storage contract

Each country has its own regulations and requirements for importing frozen stallion semen. These can be accessed at: or contact the ERL at (970) 491-8626.
Equine Reproduction Laboratory
ERL Giving Fund
Contact Us:
​3101 Rampart Road
Fort Collins, Colorado 80523-1693

​(970) 491-8626

(970) 491-7005