Three Ways Stallion Owners Can Prevent Unapproved Use of Frozen Semen

August 29, 2011

As breeding season is coming to a close, many of you may be wondering what you should do about unused doses of frozen semen that remain in the possession of your mare owners and what you should do with returned semen. Stallion owners often express concern that if frozen semen is sold as part of a breeding contract, unused doses of semen remaining after the original mare becomes pregnant may be sold to a 3rd party or used to inseminate another mare without payment of any additional stud fees. But, if frozen semen is returned, how can you know if the semen quality has been compromised and what should you do with it? Here we offer some advice on how to minimize the amount of unused frozen semen that is outstanding at the end of the breeding season and how to handle the fate of this frozen semen in your breeding contracts and if it gets returned.

1). Minimize the number of doses you ship at any one time

When selling frozen semen as part of a breeding contract, as opposed to by the dose, we recommend our stallion owners ship two doses per cycle. This allows the mare owners and/or their veterinarians to manage the mare using a convenient two dose timed insemination protocol. If the mare does not conceive on the first cycle, additional shipments can be requested for each subsequent cycle. This is the best way to limit the amount of unused semen that might be retained by your mare owners. If you send more than two doses of frozen semen per cycle, or the entire season’s allocation of semen in one shipment, there is a greater likelihood that doses will be left over.

Also, allow your mare owners a sufficient tank rental period. By using traditional frozen semen vapor shippers that can hold temperature for 1-3 weeks, the semen can remain in the tank for the duration of the heat cycle and any unused semen could be returned with the tank. If rental of the shipper is limited to 2-3 days and the mare is not quite ready to be bred, the mare owner is more likely to transfer the semen to storage in order to return the tank. Once transferred to storage at another location it is going to be more difficult to get it back.

2). Be clear in your contract about who owns the frozen semen and what should be done with unused doses

When frozen semen is sold as part of a breeding contract, with a specified number of doses provided per cycle or per breeding season, the frozen semen is owned by the stallion owner - this should be clearly stated in your contract. This is in contrast to the situation when frozen semen is sold by the dose. Semen sold by the dose becomes the immediate property of the mare owner and depending upon the contract of sale, the stallion owner may lose any control over how the frozen semen is managed or sold from that point forward.

In addition, specify how much frozen semen is provided per breeding season and on a per cycle basis, outline instructions on what should be done with any unused semen and indicate what options the mare owner has if additional frozen semen is required (i.e. can they purchase additional doses for a per dose fee or can they return for service the following year). The mare(s) to be inseminated should be identified in the contract and any substitutions of mares should be approved by the stallion owner. A contract usually states that the semen is to be used on the specified mare(s) only and breeding to any additional mares requires payment of additional stud fees. Remember, in this age of reproductive technology, multiple foals could still be produced from one mare, so outline what rules are in place for embryo transfer. If the mare owner intends to use the semen in assisted reproductive techniques they must disclose this to the stallion owner and usually an additional stud fee is required for each foal put on the ground.

Informing your mare owners of their responsibilities before entering into a breeding contract will avoid unnecessary confusion or disagreement in the future and is critical to ensuring compliance when it comes to returning or destroying unused semen.


There are essentially two options for unused doses of frozen semen:

Destroy It - The best way to ensure any remaining semen is not used for purposes other than originally intended is to request it be destroyed. A common practice is to have the mare owner or veterinarian thaw the frozen semen and either sign a statement attesting that the straws were thawed, or as an extra precaution return the unopened, thawed straws in the mail.

Return It - The viability of frozen semen depends on proper handling and storage, maintaining straws at liquid nitrogen temperatures and minimizing any exposure to temperatures >-100°C. Once semen has left permanent storage it is difficult to verify the integrity of the frozen semen; it could have been damaged during shipment, transfer or handling. It would be unethical to sell potentially compromised semen. However, some stallion owners reserve returned semen for use in breeding their own mares, so the return of potentially usable doses of frozen semen is preferable to destroying the semen, particularly if the semen is in short supply. In cases where the inventory of frozen semen is extremely limited returned doses may need to be utilized to fulfill future frozen semen contracts. In this case a straw from each returned breeding dose could be submitted for motility analysis, in order to confirm the original semen quality. If unused semen is to be returned, be sure to specify in your contract exactly how and when it must be returned and who is responsible for the cost.

3). Institute a means to track how many doses of frozen semen are used

We recommend that stallion owners require the inseminating veterinarian to sign an insemination certificate that specifies the identity of the mare that was inseminated, the dates the inseminations were performed, how many doses of frozen semen were used, how many doses of frozen semen remain and indicate that any unused doses were returned or destroyed (as per the contract). The insemination certificate can be included in the paperwork that accompanies the frozen semen shipment and once completed by the veterinarian can be faxed or mailed back to the stallion owner. Some stallion owners will not ship semen for an additional cycle if the insemination certificate from the previous cycle has not been returned.

See Also FAQs:
- How Should I Sell Frozen Semen?
- Why Does SBS Recommend Selling Frozen Semen As Part of a Contract Rather Than By the Dose?
- How Many Doses of Frozen Semen Should I Ship Per Cycle?