The sperm mitochondrion (pictured left) is one of the most damaged organelles during cryopreservation and is likely responsible for the majority of loss in motility and fertility after a freeze-thaw cycle. Our laboratory at UC Davis has focused on developing an increased understanding of mitochondrial bioenergetics in sperm that could provide strong rationale for marked improvement in preservation and assisted reproduction techniques.
Quick Tip videos about equine frozen were produced as a follow up to the “Frozen Semen for Mare Owners” four-part video series created by Select Breeders Services (SBS) and the Dutch Warmblood Studbook in North America (KWPN-NA). Click below for links to the six “Quick Tip” videos which explain the types of extenders used to process frozen semen, motility, questions to ask frozen semen distributors and more. Each informational video is less than five minutes long.
In 2020, Select Breeders Services (SBS) and the Dutch Warmblood Studbook in North America (KWPN-NA) collaborated on a project to produce a video series, “Frozen Semen for Mare Owners”. The KWPN-NA recognized many of their breeders use frozen semen in their breeding programs while other members are considering the use of frozen semen but may not know the right questions to ask or what they should expect. Natalie DiBerardinis, Managing Director of Hilltop Farm, Inc. and member of the KWPN-NA Stallion Committee said, “A lot of the frozen semen information is written towards the stallion owner perspective, so we want to take the approach of what mare owners need to know.”
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’.
I have always been fascinated by the exquisite design of biological systems. The more we humans understand about biology, the more we realize we don’t know. The process of mammalian fertilization is one of these complex biological systems that in nature requires the proper coordination of so many factors ranging from the behavior of male and female to biochemical changes at the cellular and molecular level. Defined as: “A process in sexual reproduction that involves the union of male (sperm) and female (ovum) gametes (each with a single, haploid set of chromosomes) to produce a diploid zygote”, fertilization requires that functionally viable sperm, at the right stage of maturity, are present in the oviduct of the mare during a brief window of time when a functionally viable oocyte is present.
One concern some mare owners and veterinarians have with using equine frozen semen is the MYTH that it is difficult to thaw and breed a mare with it...this is not true. The process of thawing frozen semen is fairly simple if you have the right tools. Also, inseminating a mare with frozen semen isn’t any different than inseminating her with cooled or fresh semen, unless you are using a deep horn insemination technique. The only concern is that one must follow the specific thawing instructions precisely in order to obtain maximum post-thaw survival. This requires careful attention to detail and a temperature controlled water bath.
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.
Many stallion owners have the foresight to have frozen semen processed from their stallions while they are young, during their prime reproductive years. It may be too late if one waits until after his show career is complete, he is older or for any other reason because there is no guarantee of tomorrow. Waiting may turn into a situation of “I wish I would have…”. When semen is frozen earlier in a stallion’s life, it becomes a tool for the stallion owner to not only perpetuate the genetic line of their stallion but also allows for continued income after the stallion has passed away. Also, some owners have looked at frozen semen as an insurance policy for their valuable stallions. Regardless of why or when the semen is frozen, the management of it will likely change once he passes away.
For veterinarians and technicians accustomed to inseminating fresh or cooled semen in large (20-60 ml) volumes, the idea of inseminating 0.5 to 4 ml of thawed frozen semen can be intimidating. During processing, frozen semen is concentrated by centrifugation and is typically packaged in small 0.5 ml straws at a sperm concentration that is often as much as 5 to 10 times greater than cooled semen. Therefore, a full insemination dose of frozen semen may be contained in just a few milliliters of volume whereas the same number of sperm extended for cooling may require 30-40 ml of volume.
Select Breeders Services (SBS) can assist stallion owners with their equine frozen semen needs whether the semen required is for domestic use, to be qualified for export, needed to breed a handful of mares or hundreds of doses for storage. As the world’s largest provider of equine frozen semen services, we are continuously adding new stallions to the list of more than 3,500 stallions already frozen within the SBS Affiliate Network. Discussed in this article will be questions we ask about stallions prior to their arrival, disease testing required prior to entry, what happens after he arrives, our storage and distribution program as well as how our customer service extends well beyond the stallion’s departure from our facility.
The test freeze is the first freeze performed on a stallion when he comes to a Select Breeders Services (SBS) Affiliate Lab to have semen frozen. We primarily have four different semen freezing protocols that we test on each stallion. The differences between each protocol being in either the extender formulation or the rate of cooling. For subsequent freezes we choose the protocol which gives the best results as determined by post-thaw motility. Regardless of the protocol, once the straws of semen reach -120 degrees Celsius in the programmable cell freezer they are then plunged into a bath of liquid nitrogen at -196 degrees Celsius.
The SBS network of affiliates is the acknowledged leader in the field of cryopreservation of equine semen. Each year we freeze thousands of ejaculates equating to tens of thousands of doses. When SBS was founded the company leadership made a commitment to quality of the finished product above all else. We wanted to put technology to use to help grow the equine frozen semen AI industry in the most responsible manner possible. It was clear early on that one of the major factors limiting the application of frozen semen in the horse industry was inconsistent quality of the product being put on the market. Breeders and veterinarians experienced frustration with attempts to use expensive semen that in many cases was of very poor quality. We knew that in order for breeders to realize the full potential of frozen semen technology they would have to be convinced that by applying strict standards for quality, frozen semen could be produced to achieve results similar to cooled semen. We also knew that these results would have to be produced in an efficient and economical way. Quality became the cornerstone upon which we would build our business.
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”.
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.
What happens when you breed a 22 year old maiden mare with frozen semen processed in 1989? It is no secret the first commercial client stallion whose semen was frozen by SBS was the 1984 Olympic medalist, Abdullah (Donauwind x Abiza). He was a beautiful grey Trakehner stallion owned by Terry and Sue Williams of New York. He passed away in January 2000 at the age of 29 years old. Recently, Sue contacted Paul Loomis to tell him a story about an Abdullah colt (photo left) born this year…fourteen years after the stallions death. Yet, that wasn’t the only interesting part of the story she had to tell.
You have made the decision to breed your mare using frozen semen, now what? The choice of breeding your mare with frozen semen over cooled or fresh semen has a few notable benefits. Aside from the expanded availability of stallions available to you with frozen semen, e.g. those that are located in another country, are limited by their competition schedule or are deceased, another big advantage of frozen semen is that the shipment can be sent out ahead of time so it is ready and waiting on your mare to ovulate; as opposed to your mare waiting on the semen to be collected from the stallion, processed and cooled, and finally shipped out to you. Nonetheless, despite this added convenience, it is important to be prepared and plan ahead for your frozen semen shipment. That way you are fully prepared when the time comes to request and receive your shipment in order to optimize your chance of a successful breeding.
The sudden death of a stallion is a devastating event, not just emotionally, but potentially financially as well. In addition to any competitive goals the stallion was working towards, his untimely death may mean the loss of future breedings, particularly if a stock of frozen semen was not banked up whilst he was alive. In this situation it may be possible to harvest and freeze epididymal sperm by castrating the stallion immediately after death or euthanasia. Alternatively, collection and freezing of epididymal sperm may be an elective procedure performed at the time of castration. This offers an advantage to young stallions, i.e. some semen can be frozen without taking time out from a busy training schedule, or without exposing a young stallion to the breeding environment. For the mature stallion it represents an additional opportunity to collect semen for freezing. Here we review the process of epididymal sperm harvesting for freezing, and its subsequent application for breeding purposes.
The advantages and disadvantages of utilizing equine frozen semen are debated by stallion and mare owners alike. Will I continue to show my stallion or retire him to the breeding shed? Is there an international market for my stallion? What if my stallion is injured in an accident or suddenly dies? Is my mare a suitable candidate for breeding with frozen semen? Is it true conception rates with frozen semen are lower than those when using cooled semen? These are just a few questions to ask when considering whether to utilize equine frozen semen.
The most commonly used measure of semen quality is sperm motility, specifically “progressive motility”. But what exactly does that mean and how is it determined? The minimum post-thaw “progressive motility” generally recommended for commercial distribution of frozen semen is 30% to 35%. This article will address some of the factors that can affect the assessment of sperm motility as well as the various problems associated with techniques used for determining “progressive motility”.
Is a dose a breeding? Is a straw a dose? How many straws in a dose? How many sperm in a dose? These are often questions we hear from our clients when purchasing or using frozen semen. There is so much variability in the format of doses sold throughout the world that it can be confusing at times. To ensure you have the best opportunity of success when breeding your mare it is important to understand all the elements that determine an adequate dose of frozen semen. Here we review frequently asked questions that relate to what constitutes a dose of frozen semen.
Every shipment that we send from Select Breeders Services includes an envelope of materials, zip tied to the top of the frozen semen shipper, that provides information about the semen we are sending to you. Included in the envelope are the following items: - Transaction Report - Safety Notice for Handling Frozen Semen - Thawing and Handling Instructions - Info sheet on Management of Mares with Frozen Semen - Return FedEx airbill and address label - Info notice regarding tank rental and return - Additional materials may include notices prepared by the stallion owner that they have requested us to include with the shipment, e.g. breeding and insemination certificates.
How many sperm does it take to get a mare pregnant? 1
billion?...500 million?... One? Actually, any one of those answers could
be correct under certain conditions. The only way to really answer that
question is... "it depends". Fertilization is a complex process
requiring that both the sperm and egg possess a myriad of functional
attributes expressed at the right time and in the right place. A motile
sperm is not necessarily a fertile sperm. So, how many sperm must be
deposited in the mare for "acceptable" fertility? It would seem that
this would be the logical basis for determining sperm numbers in an
insemination dose for commercially distributed semen. To achieve the
goals of both the mare and stallion owner it is necessary for each dose
of semen to contain sufficient numbers of functionally competent sperm
to maximize the probability of conception. The relationship between
sperm number and fertility is expressed as a typical dose response curve
(see figure1). However, the slope of the curve and the maximum level of
fertility are different for individual stallions.
In recent issues of the SBS monthly newsletter we presented a couple of blog articles about reproductive efficiency, titled Measuring Reproductive Efficiency and A Review of Reports of Reproductive Efficiency. At SBS we ship out 1000s of frozen semen shipments a year, however, it is very difficult for us to get the pregnancy data back from the mare owners we send semen to. In the future we hope to simplify this process by enabling our clients to respond to an automatically generated email through our website. This would be great information to have available for review by mare owners considering frozen semen. We do track fertility data for the mares and stallions we manage at our SBS affiliate locations and we try to combine this data as a group for analysis. We summarize this information for you here.
There are a number of misconceptions about frozen semen that are pervasive in the horse breeding community and one of them relates to the relative costs of frozen vs. cooled semen. We have heard horror stories of mare owners spending thousands of dollars purchasing and then trying to get mares in foal with frozen semen only to end the season with an open mare. Then there are also stories of stallion owners investing large sums of money freezing semen that is of poor quality or doesn’t result in pregnancies. Many of these nightmares are the result of lack of quality control on the semen that is put on the commercial market and/or proficiency of the lab or technician that is freezing the semen. Poor quality semen, whether fresh, cooled or frozen will result in wasted money, empty mares and unhappy breeders. This article will present objective information on the true costs of using frozen semen so that stallion and mare owners can make informed decisions.
Following up on our Blog article of last month Should the US Adopt Stricter Controls on Cooled and Frozen Semen Production Facilities, we thought it might be interesting to present some data to demonstrate the variability in the quality of frozen semen being imported into the US. For the purposes of this blog article we combined the data from client samples submitted for post-thaw analysis in the last 1-3 yrs. A post-thaw analysis is one of the services we offer to our clients importing frozen semen; we evaluate post-thaw motility by computer assisted sperm analysis (CASA), sperm concentration using the Nucleocounter and we perform a bacterial culture of the semen to check for mare pathogens.
You know the value of your stallion…X amount of dollars, your
broodmares…X amount of dollars, and your stallion’s offspring…X amount
of dollars. But if asked the value of your stallion’s frozen semen you
may answer “I don’t know” or “Priceless.” Why do you
need to know the value of your stallion’s frozen semen? Unfortunately,
stallions pass away, partnerships dissolve due to sales or divorce,
bankruptcies are filed, semen is exported, etc. and in these cases you
need to be prepared to handle your frozen semen as an asset. The value
of frozen semen can be determined either by the cost of production or
the number of breedings that potentially could be sold.
There is no expiration date on frozen semen. As long as the semen is properly maintained at the correct temperature in a liquid nitrogen storage tank, the working life of frozen semen is believed to be nearly unlimited. At SBS we have produced pregnancies with semen stored for more than 20 years. By utilizing the highest quality freezing extenders available, computer controlled rate cell freezers and maintaining rigidly controlled storage conditions, SBS maximizes the duration of sperm survival.
It’s always exciting for us at SBS to hear about the success of
breeding with frozen semen and the horses that have been produced via
this method. We were particularly intrigued by an article published
last summer at the beginning of the prestigious Aachen jumper show in
Germany. On July 16, 2010 a then 12 year old Oldenburg gelding named
Ferrari won the RWE Prize of North-Rhine Westphalia at the opening of
Aachen. What makes this horse special, other than his ability, is that
he was conceived via frozen semen. His influential sire, Furioso II,
passed away 24 years ago, 11 years prior to the breeding of Ferrari and
because of frozen semen these valuable genetics are still present today.
To read the full article that caught our eye click here.
Please Note - photos used in these news articles are available in the public domain, have been purchased through istockphoto or (when referencing breeders or horses) have been submitted to
Select Breeders Services Inc. by the breeding farm or horse owner.
Photo credit has been provided where applicable. If at anytime you see something that needs to be addressed please feel free to contact us directly.
The sperm mitochondrion (pictured left) is one of the most damaged organelles during cryopreservation and is likely responsible for the majority of loss in motility and fertility after a freeze-thaw cycle. Our laboratory at UC Davis has focused on developing an increased understanding of mitochondrial bioenergetics in sperm that could provide strong rationale for marked improvement in preservation and assisted reproduction techniques.
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: ‘
I have always been fascinated by the exquisite design of biological systems. The more we humans understand about biology, the more we realize we don’t know. The process of mammalian fertilization is one of these complex biological systems that in nature requires the proper coordination of so many factors ranging from the behavior of male and female to biochemical changes at the cellular and molecular level. Defined as: “A process in sexual reproduction that involves the union of male (sperm) and female (ovum) gametes (each with a single, haploid set of chromosomes) to produce a diploid zygote”, fertilization requires that functionally viable sperm, at the right stage of maturity, are present in the oviduct of the mare during a brief window of time when a functionally viable oocyte is present.
One concern some mare owners and veterinarians have with using equine frozen semen is the MYTH that it is difficult to thaw and breed a mare with it...this is not true. The process of thawing frozen semen is fairly simple if you have the right tools. Also, inseminating a mare with frozen semen isn’t any different than inseminating her with cooled or fresh semen, unless you are using a 
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 
Many stallion owners have the foresight to have frozen semen processed from their stallions while they are young, during their prime reproductive years. It may be too late if one waits until after his show career is complete, he is older or for any other reason because there is no guarantee of tomorrow. Waiting may turn into a situation of “I wish I would have…”. When semen is frozen earlier in a stallion’s life, it becomes a tool for the stallion owner to not only perpetuate the genetic line of their stallion but also allows for continued income after the stallion has passed away. Also, some owners have looked at frozen semen as an insurance policy for their valuable stallions. Regardless of why or when the semen is frozen, the management of it will likely change once he passes away.
For veterinarians and technicians accustomed to inseminating fresh or cooled semen in large (20-60 ml) volumes, the idea of inseminating 0.5 to 4 ml of thawed frozen semen can be intimidating. During processing, frozen semen is concentrated by centrifugation and is typically packaged in small 0.5 ml straws at a sperm concentration that is often as much as 5 to 10 times greater than cooled semen. Therefore, a full insemination dose of frozen semen may be contained in just a few milliliters of volume whereas the same number of sperm extended for cooling may require 30-40 ml of volume.
Select Breeders Services (SBS) can assist stallion owners with their equine frozen semen needs whether the semen required is for domestic use, to be qualified for export, needed to breed a handful of mares or hundreds of doses for storage. As the world’s largest provider of equine frozen semen services, we are continuously adding new stallions to the list of more than 3,500 stallions already frozen within the SBS Affiliate Network. Discussed in this article will be questions we ask about stallions prior to their arrival, disease testing required prior to entry, what happens after he arrives, our storage and distribution program as well as how our customer service extends well beyond the stallion’s departure from our facility. 
The test freeze is the first freeze performed on a stallion when he comes to a Select Breeders Services (SBS) Affiliate Lab to have semen frozen. We primarily have four different semen freezing protocols that we test on each stallion. The differences between each protocol being in either the extender formulation or the rate of cooling. For subsequent freezes we choose the protocol which gives the best results as determined by post-thaw motility. Regardless of the protocol, once the straws of semen reach -120 degrees Celsius in the programmable cell freezer they are then plunged into a bath of liquid nitrogen at -196 degrees Celsius.
The SBS network of affiliates is the acknowledged leader in the field of cryopreservation of equine semen. Each year we freeze thousands of ejaculates equating to tens of thousands of doses. When SBS was founded the company leadership made a commitment to quality of the finished product above all else. We wanted to put technology to use to help grow the equine frozen semen AI industry in the most responsible manner possible. It was clear early on that one of the major factors limiting the application of frozen semen in the horse industry was inconsistent quality of the product being put on the market. Breeders and veterinarians experienced frustration with attempts to use expensive semen that in many cases was of very poor quality. We knew that in order for breeders to realize the full potential of frozen semen technology they would have to be convinced that by applying strict standards for quality, frozen semen could be produced to achieve results similar to cooled semen. We also knew that these results would have to be produced in an efficient and economical way. Quality became the cornerstone upon which we would build our business.
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.
What happens when you breed a 22 year old maiden mare with frozen semen processed in 1989? It is no secret the first commercial client stallion whose semen was frozen by SBS was the 1984 Olympic medalist, Abdullah (Donauwind x Abiza). He was a beautiful grey Trakehner stallion owned by Terry and Sue Williams of New York. He passed away in January 2000 at the age of 29 years old. Recently, Sue contacted Paul Loomis to tell him a story about an Abdullah colt (photo left) born this year…fourteen years after the stallions death. Yet, that wasn’t the only interesting part of the story she had to tell. 
You have made the decision to breed your mare using frozen semen, now what? The choice of breeding your mare with frozen semen over cooled or fresh semen has a few notable benefits. Aside from the expanded availability of stallions available to you with frozen semen, e.g. those that are located in another country, are limited by their competition schedule or are deceased, another big advantage of frozen semen is that the shipment can be sent out ahead of time so it is ready and waiting on your mare to ovulate; as opposed to your mare waiting on the semen to be collected from the stallion, processed and cooled, and finally shipped out to you. Nonetheless, despite this added convenience, it is important to be prepared and plan ahead for your frozen semen shipment. That way you are fully prepared when the time comes to request and receive your shipment in order to optimize your chance of a successful breeding. 
Every shipment that we send from Select Breeders Services includes an envelope of materials, zip tied to the top of the frozen semen shipper, that provides information about the semen we are sending to you. Included in the envelope are the following items:
In recent issues of the SBS monthly newsletter we presented a couple of blog articles about reproductive efficiency, titled 
There is no expiration date on frozen semen. As long as the semen is properly maintained at the correct temperature in a liquid nitrogen storage tank, the working life of frozen semen is believed to be nearly unlimited. At SBS we have produced pregnancies with semen stored for more than 20 years. By utilizing the highest quality freezing extenders available, computer controlled rate cell freezers and maintaining rigidly controlled storage conditions, SBS maximizes the duration of sperm survival.
It’s always exciting for us at SBS to hear about the success of
breeding with frozen semen and the horses that have been produced via
this method. We were particularly intrigued by an article published
last summer at the beginning of the prestigious Aachen jumper show in
Germany. On July 16, 2010 a then 12 year old Oldenburg gelding named
Ferrari won the RWE Prize of North-Rhine Westphalia at the opening of
Aachen. What makes this horse special, other than his ability, is that
he was conceived via frozen semen. His influential sire, Furioso II,
passed away 24 years ago, 11 years prior to the breeding of Ferrari and
because of frozen semen these valuable genetics are still present today.
To read the full article that caught our eye click 
Julie Skaife at SBS-MD recently responded to FAQ presented by the American Connemara Magazine in the article, 
