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There are numerous advantages of frozen semen. If maintained properly in liquid nitrogen, frozen semen will last indefinitely. This allows frozen semen to be shipped to the mare and the mare bred at the most opportune time, close to the time of ovulation. One other use of frozen semen that seems to be gaining in favor is for farms to ship frozen semen to mares when there is a shortage of cooled semen. Alternatively, the breeding farm uses frozen semen to breed mares housed at the farm and ships out the cooled semen. Thus, frozen semen becomes the "backup plan" for breeding mares. You can find additional information to consider when deciding if frozen semen is a fit in your breeding program by reading these articles on the SBS Website: ‘Why Freeze Stallion Semen?’, ‘The Pros and Cons of Equine Frozen Semen’ and ‘The Hidden Value of Frozen Semen’.

To understand why seminal plasma is beneficial in some situations and potentially harmful in others we must first review what it is, where it comes from and what we think are its roles in reproduction. The term seminal plasma refers to the fluid portion of ejaculated semen in which the spermatozoa are suspended. This fluid consists of secretions from the accessory sex glands in the stallion’s reproductive tract. These include the ampullae, the vesicular glands (seminal vesicles), the prostate gland and the bulbourethral glands (figure 1).

Once equine semen is frozen it is recommended that a post-thaw analysis be performed in order to ascertain the semen quality. There is variability in how well sperm from different stallions respond to the cellular stress of freezing and thawing. It is important to determine how well the sperm from a particular stallion withstood the stress of cryopreservation in order to make informed decisions regarding the management of their frozen semen inventory and breedings. Also, when we freeze a stallion for the first time we do a test freeze comparing several different protocols. We then use the post-thaw motility to select the freezing protocol for subsequent collections which gives the best post-thaw result. There are industry recommended minimums for commercial distribution of equine frozen semen and therefore it is pertinent to know if your stallion’s frozen semen would qualify. Consequently, the analysis of frozen-thawed semen is a valuable tool for the semen freezing lab, but also for the veterinarian receiving the semen. Your vet may base the breeding management of your mare upon the post-thaw quality of the semen. Also, many vets take a look at the motility of the frozen semen at the time of insemination, for future reference if there are concerns should the mare not check in foal.

Whether a mare is maiden, recently foaled, or barren can influence her ability to conceive when breeding her with frozen semen. The first pregnancy obtained by using frozen-thawed semen in the equine species dates back to 1957 and was obtained using epididymal semen. However, for many years this reproductive technology has achieved limited progress in the horse compared with other species such as cattle. This was mainly because for a very long period of time only a few horse registries allowed the use of frozen-thawed semen. Hence, economic interests and resources allocated to research have always been minimal and as a result obstructing advances in this area.

How a stallion owner/manager responds to and handles mare owner concerns regarding semen quality or fertility can make or break a relationship or reputation. This article aims to give stallion owners an overview of the factors involved and provide a systematic guide to troubleshooting a resolution if possible. In Part 1 of this article, published in last month’s newsletter, we discussed the stallion’s breeding history, the importance of a breeding soundness exam (BSE), and stallion management practices as well as semen quality and evaluation. This month in Part 2, we will review common problems identified after the semen evaluation, the relevance of the mare book and their reproductive status and discuss the topic as it relates to those stallions breeding with frozen semen.