Timed artificial insemination (AI), programmed AI, one dose, two doses, deep horn insemination…what’s best for your mare? With the increased use of frozen semen and the trend towards commodity sales (by the dose with no guarantee) veterinarians have developed a variety of strategies when managing mares being bred with frozen semen. In this article, we discuss several options and which ones might be most appropriate for your situation.
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.
Further expansion in the use of frozen semen is dependent upon developing simplified strategies for insemination. SBS has developed a timed insemination protocol where mares are only examined once per day during estrus and inseminated at 24 and 40 hr after hCG or 30 and 40 hr after GnRH. This approach allows frozen semen mares to be managed similar to those bred with cooled shipped semen. A couple of arguments against this approach with frozen semen is that it takes too much semen when mares are bred twice in one cycle and that if the mare is inseminated more than once per cycle the fertility will be lowered because of post-breeding induced endometritis.
Stallion owners and managers can encounter reluctance from mare owners to use frozen semen. This may be due, in part, to commonly spread misinformation regarding the fertility of frozen semen and the misconception that frozen semen is difficult to use. This hesitancy seems especially true if the frozen semen of a particular stallion has yet to be used in order to establish evidence of fertility. If one can offer specific credible evidence of the fertility of frozen semen from a given stallion it can go a long way towards promoting the process and breedings to your stallion. For more information please read “Frozen Semen Myths and Misconceptions” as well as our blog article regarding “The Pros and Cons of Equine Frozen Semen”. In this article, Dr. Brian Carroll of Oklahoma City Equine Hospital, discusses why a frozen semen fertility trial should be performed, how to go about performing the fertility trial and provides an example of a frozen semen fertility trial he performed.
All too often we hear tragic stories about the sudden death of a stallion whether it be due to an illness or an accident no one anticipated. He may have been a mature stallion who was already proving himself as a sire or a young stallion but now the world will never know his genetic capabilities. These conversations usually end with the stallion owner saying, “I wish I had frozen semen from him.” Or a mare owner saying, “I wish they had frozen semen on him because he would have been a wonderful cross with my mare.” It doesn’t have to be this way.
“I just purchased one very expensive dose of frozen semen from this incredible stallion. Is it OK to split the dose and breed two mares to try and get two foals?” or “The stallion owner only provides one dose per heat cycle and my vet would like to use a timed insemination protocol. Is it OK to split the dose and inseminate twice on the heat cycle?” At SBS we have heard these questions or some variation of them many times over the years. The answers are not simple ones. This blog article will follow up on two previous blogs that are also important in understanding the issue. See the recent blogs What Exactly is a Dose of Frozen Semen? and What is Progressive Motility?
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