Managing Director, Hilltop Farm
The big topic of discussion this spring and summer for many sport horse breeders in both North America and Europe has been Warmblood Fragile Foal Syndrome (WFFS). The news first broke in March when we released the carrier status of one of the Hilltop Farm stallions. For a syndrome with a very low occurance rate, has the response been overblown or are we not doing enough? In the four months that have passed, there have been many developments that I feel are important for breeders to know and understand. It is the voices of breeders that will direct how this and future genetic testing is or is not utilized within sport horse breeding.
The initial responses from the North American sport horse registries was quite positive. They acknowledged member concerns and encouraged mare owners to test. An especially significant development out of this support from the registries was that UC Davis started offering the WFFS test as well. As you probably are aware, UC Davis handles the DNA parentage verification for almost all the registries in North America. The ability to cross-check on identity verification, the opportunity for a large-scale population study to better evaluate the carrier rate, and UC Davis's excellent reputation all are important components in the significance of this development. Many of the breed registries have negotiated discounted rates on testing and you can often use DNA that is already on-file at UC Davis if your registry requires hair samples for proof of parentage at time of registration.
The Dutch (effectively immediately) and Swedish Warmblood (have begun testing but not mandatory until 2019) registries in both Europe and North America are going to require testing of all approved stallions and are openly publishing testing results. The American Hanoverian Society (although notably not the Hanoverian Verband) are encouraging stallion owners to test and will include testing status in their yearly directory. ISR/OldenburgNA has requested stallions to be tested, but hasn't yet announced if/how those results will be published. Other registries are taking a more cautious approach, recommending testing but not going so far as to require it and a few registries are completely silent on the WFFS question. WFFS and genetic health in general will be a major topic of the World Breeding Federation for Sport Horses annual meeting this year and it's likely we'll see some registries waiting to make an official decision until after that meeting.
Notice none of the registries are requiring testing for mares at this time, although those that have made statements have encouraged mare owners to test. I feel this has been an underemphasized step to-date. WFFS is an autosomal recessive trait, meaning a foal can only be affected if the foal inherits the disease from both parents. When the Friesian breeders were facing similiar sorts of recessive traits they have taken the approach of testing the mares as the top priority. That way a breeder was guaranteed knowledge for at least one side of the breeding equation. While a stallion is likely to have a much larger impact on the population as a whole, it is our mares that have the largest impact within our own breeding results and as such we need to know everything we can about them. A breeder that tests their own mares will know either that their mare is clear of the mutation and regardless of the stallion’s status a foal would not inherit the actual expression of the disease OR that the mare is a carrier and while she herself won’t have any health risks, it will be important to know the status of potential stallion combinations for her and choose only to breed to a stallion who is himself clear of the recessive allele.
I can understand the breeders taking the position of not wanting to test, but I do not agree with them. Yes, there are many far larger issues confronting breeders that we need to be concerned with in our breeding choices and yes, the incidence rate of affected foals is very low. But with all we spend on our horses, why would we not reduce the risks of something going wrong when we can? This test is easy and inexpensive. If we test breeding stock in this generation, we'll have a lot of offspring for subsequent generations that won't need tested as it automatically applies that if both parents are free of the gene mutation than the offspring are as well.
For those of us with carrier horses, we now have important information we didn't have a few months ago. While there is a 50% chance a carrier horse will pass along carrier status to their offspring, as long as we avoid carrier-to-carrier breedings we can prevent any potential foal losses due to WFFS. There are strong opinions on both sides for allowing or not allowing carrier stock to be bred but the cautious, longview approach that has been adopted by all other registries in dealing with similiar situations has been to require testing, avoid potentially risking combinations, and focus on education of breeders and the general riding public.
For those of you who have tested, been active in the online discussions, or contacted your registry with your thoughts - thank you! Please continue to do so as we are a long ways from all the registries having full plans in place for handling the question of WFFS testing. I fully expect we'll be having similiar discussions in coming years regarding other genetic traits as testing becomes more available and how we respond to WFFS will shape how future tests are integrated as well.
Report by Alice Knox
The inaugural Adequan West Coast Dressage Festival was warmly welcomed to the Southern California dressage scene in January, and already many are looking forward to the event’s return next year. WCDF president Scott Hayes described the festival as “Not only competitions, but a gathering place for the dressage community to socialize, learn, and grow brands and businesses in this spectacular part of the horse world.” Designed primarily as a means to provide multi-week, winter-time FEI competition without having to fly horses, clients and supplies to southern Florida, the San Diego tournament handily accomplished the mission.
The location was the beloved Del Mar Fairgrounds, fondly referred to as “Where the turf meets the surf”. The showgrounds are regarded as the best on the West Coast, with permanent shed row stabling and roomy stalls. Arena footing is maintained by the same equipment used on the adjoining race track, site of the 2018 Breeders Cup Championships. The sparkling Pacific Ocean is directly to the west, and the charming village of Del Mar to the south. To the east are equestrian communities where San Diego’s resident dressage Olympians, namely Peters, Seidel and Traurig, have their training barns. The weather was typical for southern California at this time of year - warm, dry, sunny days with crispy cool nights. Wear short sleeves during the day, and put on a puffy jacket when the sun goes down.
Show management’s attention to detail included dressing up the indoor arena with classy black linens and glowing table lamps on the VIP box seat tables. The ringside Hospitality Lounge didn’t disappoint and provided a lively meeting place for riders, trainers, owners and friends. The comfy couches, full bar and view of both the competition ring and golden Pacific sunsets were quite inviting. Hungry? A café just outside the lounge prepared fresh, made-to-order breakfast, lunch and dinner items.
The four weeks of top competition, along with Master Class exhibitions, attracted exhibitors throughout the West Coast and British Columbia. Those who wanted to experience the event but couldn’t attend were treated to free livestreaming on the horse show’s Facebook page, with expert commentary provided by retired FEI 5* star judge (and San Diegan) Axel Steiner. Master Class clinics featured equestrian celebrities Monty Roberts, Boyd Martin, Laura Graves, Helen Langenhanenberg, and Charlotte Dujardin. General admission to the presentations was simply a suggested donation to the international animal welfare organization Brooke USA. By making the show easily accessible to so many, the West Coast Dressage Festival created an instant fan base that will happily support the event next year.
The USSHBA was well represented at the festival. Congratulations to breeder and USSHBA board member Maggie Neider of North Hill Farm in New York. During the show’s final weekend, Maggie’s home bred Rosalut NHF (Rosenthal x Legacy x Salut) continued his success in the dressage ring by winning the CDI 1* Intermediate 1 class with 70.41%, out of 14 entries. The 8 year old Oldenburg was ridden by Carly Taylor-Smith of Malibu, California for owner Nikki Taylor-Smith. USSHBA was also an event sponsor, and our full page, color advertisement in the show program introduced the West Coast dressage community to our organization.
More information on the Adequan West Coast Dressage Festival info can be found here.
There is no one-stop, comprehensive database at this time that crosses all sporthorse breeds, disciplines, countries, etc. With the crossing of bloodlines across registries, you’ll need to be very resourceful and explore multiple research options to gain a more complete representation. The following resources are listed as some suggestions to get you started along with some notes as to why/how we use various sites. There are pros and cons to users being able to edit data so remember to use caution when evaluating/relying on data on sites that do allow that option.
Depending on the information you are looking for, the bloodlines, and the discipline, you'll find your favorite sites to utilize. We'd love to keep adding to this list, so send in your recommendations or helpful hints to firstname.lastname@example.org.
Courtesy of Paul Loomis, Select Breeders Services
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.
Spermatogenesis (the process of sperm formation in the testes) is an ongoing process with newly formed sperm being produced constantly during the sexually mature lifespan of the male. In the stallion, spermatogenesis takes approximately 57 days from start to finish. Further sperm maturation occurs during transit of the sperm through the epididymis where motility and fertilizing capacity is acquired. Mature sperm are then stored in the tail of the epididymis and the ampulla until ejaculation. At ejaculation, the sperm are exposed to factors in fluid from the accessory sex glands that are important in protecting the sperm from the immune system of the mare. Once ejaculated into the mare’s uterus the sperm undergo further changes in response to specific signals from the female reproductive tract. These physical and biochemical changes (capacitation and the acrosome reaction) are required for the sperm to bind to and penetrate the oocyte and initiate fertilization. Once the changes associated with capacitation and the acrosome reaction occur, the sperm have a finite period to encounter a mature oocyte after which they rapidly die and are no longer able to participate in fertilization. So, successful fertilization requires that there are sufficient “functionally viable sperm” that have survived the transit through the female reproductive system, that are at the right stage of maturation at the right time and in the right place (oviduct) when a mature oocyte is present.
Prolonging the Lifespan of Sperm
The use of artificial insemination (AI) with cooled and frozen semen is our attempt to remove some of the natural barriers to successful fertilization such as geographical distance between sire and dam or asynchrony of optimum time for mating. AI is also used to improve efficiency of breeding by allowing for multiple mares to be inseminated from a single ejaculate. AI with frozen semen allows for International distribution of superior genetics and the possibility to access sperm from exceptional sires that are no longer fertile or even deceased.
To prolong the lifespan of sperm after ejaculation and interrupt the normal timing of sperm maturation and death, semen processing laboratories will slow down or completely halt metabolism by cooling or freezing the sperm. Without proper processing, cooling and/or freezing of sperm causes lethal damage to the cells. In this article, we will discuss the major causes of sperm damage during cryopreservation and what steps are taken to minimize that damage.
A solution consists of a solute and a solvent. The solute is the substance that is dissolved in the solvent. For example, in a saline solution, salt is the solute dissolved in water as the solvent. Ejaculated semen consists of spermatozoa in a suspension of seminal fluids. In an isosmotic (or isotonic) physiological state, the concentration of solutes dissolved in the seminal fluid is equal to the concentration of solutes within the cell. The membranes that surround the spermatozoa can allow for the movement of water and ions across the cell membrane to maintain this equilibrium and keep the osmotic pressure equal across the cell membrane.
In a suspension of cells, a solution that contains a concentration of solutes higher than that inside of the cell is hypertonic and one that has a lower concentration of solutes is hypotonic. The membranes that surround compartments of the sperm are comprised of a bilayer of various lipids and proteins (diagram above left) that are arranged to serve certain functions including transport of molecules, ions and water between the inside and outside of the cells. At body temperature, these lipid membranes are fluid and the proteins can move laterally within the membrane. At reduced temperatures, the lipids undergo phase changes from liquid to gel to solid states and the arrangement of membrane components can be altered, leading to changes in permeability, premature capacitation and eventual cell death.
Sperm Damage During Cryopreservation
The traditional theory of sperm damage during cryopreservation is the two-factor hypothesis. In this theory, the two major factors contributing to damage are:
Conversely, if the cooling is too rapid then the water doesn’t have time to move outside the cell and large intracellular ice crystals form which can physically damage the cells.
The ideal cooling curve (right) to minimize cell damage is one which is slow enough to allow for partial dehydration of the cell and avoid large intracellular ice crystal formation but fast enough to minimize damage from solution effects.
To minimize damage, sperm are suspended in extenders that contain a number of components designed to protect the sperm during cooling and freezing. In addition to salts, buffers, water and antibiotics both non-penetrating (sugars) and penetrating (glycerol, DMSO, ethylene glycol, amides) cryoprotective agents (CPA’s) are included. Freezing extenders also typically include sources of lipid and lipoprotein from egg yolk and milk. The low-density lipoproteins in egg yolk and the casein in milk are thought to protect the sperm from cooling damage and may play a role in membrane repair. Penetrating CPA’s like glycerol, ethylene glycol or the amides protect sperm by lowering the temperature at which the cells are exposed to critically high salt concentrations while non-penetrating CPA’s like lactose protect the cells through osmotic properties that promote rapid dehydration of cells.
However, evidence from recent studies with human and horse sperm indicate that with the cooling rates typically used for cryopreservation of sperm there is little or no formation of intracellular ice. Therefore, the major source of damage may be primarily due to osmotic stress caused by extracellular ice formation and the resulting changes in relative cell volume during freezing and thawing.
Let’s consider the changes in cell volume (see graph below) that likely occur during a typical freeze-thaw cycle. For horse semen cryopreservation protocols:
If the volume change exceeds the osmotic tolerance limits of the membranes then they will be irreversibly damaged and cause cell death. Species differ in the susceptibility of their sperm to damage due to cold shock and cryopreservation. These species-specific differences are thought to be related to the biochemical structure of the plasma membranes, specifically the cholesterol:phospholipid ratios, fatty acid content and membrane fluidity. It is believed that these differences are likely responsible for the differences in osmotic stress tolerance seen between species whose sperm survive cryopreservation well versus those that do not.
Male to Male Variation Within a Species
In addition to this species-specific variability, a well-documented inherent variation exists between individual males of many species in the ability of their sperm to withstand the stresses associated with freezing and thawing (cryotolerance). This male to male variation is especially evident in stallions. In dairy cattle, bulls have been selected by the AI industry for more than 50 years based on the ability of their sperm to withstand the stresses of standard cryopreservation protocols. This selection has led to an increasingly uniform and positive response to cryopreservation. Studies on membrane fluidity and osmotic stress tolerance have demonstrated that bull sperm have a much greater tolerance for exposure to hypertonic conditions than stallion sperm and that there was a 3-fold greater variance in osmotic stress tolerance between individual stallions than between individual bulls. Studies with boar sperm and human sperm have also revealed significant male to male variation in plasma membrane composition and some correlations have been found between cholesterol to phospholipid ratios, membrane fluidity, fatty acid content and response to cryopreservation. Further evidence for the relationship between membrane composition and cryosurvival comes from experiments with 4 different strains of mouse sperm that vary significantly in their cholesterol:phospholipid ratio. The percentage of motile sperm after thawing was directly correlated with the cholesterol:phospholipid ratio. The researchers were also able to dramatically improve cryosurvival in the low cholesterol strain by increasing the cholesterol content of the sperm membranes with cholesterol loaded cyclodextrins.
The SBS Difference
To date there is no single universal cryopreservation protocol that is optimum for semen from all stallions and use of a single protocol (extender, cooling rate, etc.) has led to the belief that stallions can be grouped into “good” and “bad” freezers based on post-thaw evaluation of semen frozen using a single common protocol. The SBS System for freezing stallion semen is based on the belief that semen from a large percentage of stallions in the population can be frozen successfully if an effort is made to customize cryopreservation protocols to identify optimum conditions for each individual stallion.
Our goals are to:
Excluding a champion performance stallion from a commercial frozen semen breeding program based on results from a single cryopreservation protocol is not acceptable if frozen semen is to be a significant tool in modern horse breeding.
The SBS approach employs multiple protocols that are designed to determine the optimum procedure for maximum fertility of frozen semen from each individual stallion. Standard practice for all new stallions is to perform 1 or 2 split-ejaculate test freeze procedures using a variety of extenders that contain different sources and amounts of lipids, proteins, sugars and various penetrating and non-penetrating cryoprotectants designed to control damaging cell volume excursions during freezing and thawing.
A great deal of progress has been made in the fundamental understanding of how sperm from many species are compromised during cryopreservation and this information has led to development of new extenders and protocols that have improved the results of frozen semen inseminations. Today, with improved freezing protocols leading to better quality frozen semen and a greater understanding of how to manage mares for insemination with frozen semen, this technology is more widespread than ever in horse breeding. And given the stress that we humans have placed upon nature’s exquisitely developed system of reproduction, one can marvel at how successful this technology has been so far.
Courtesy of Select Breeders Services
Breeding mares on their foal heat is a strategy used to maximize reproductive efficiency. Since income is generated from selling offspring, yearly foal production is critical to offset maintenance and breeding expenses incurred by the mare owner. With an average gestational length of 333 to 345 days, mares must become pregnant within one month post partum to continue producing foals each year. Mating mares on the first postpartum estrus is one method used to improve the chance of maintaining yearly foal production. Reviewing this topic for us is guest writer, Dr. Margo Macpherson with an excerpt from the chapter Breeding Mares on Foal Heat co-authored by Dr. Margo Macpherson and Dr. Terry Blanchard in the 2nd Edition of Equine Reproduction.
The first post partum estrus generally begins 5-12 days after foaling; hence, the terminology foal-heat or “9 day heat.” In a large study involving Thoroughbred mares, ovulation during foal heat was reported on average at 10 days post partum, with most mares ovulating within 20 days post partum (Loy, 1980). Mares that foaled early in the year were less likely to ovulate by 10 days post partum than mares foaling later in the spring. Also, early foaling mares (January to March) were more likely to have a prolonged period of postpartum anestrus (> 30 days to first ovulation postpartum) than late foaling mares. While not proven, it is suspected that the postpartum anestrus seen in many foaling mares is thus related to length of days when parturition occurs. In this regard, supplementing artificial light to late pregnant mares has been shown to reduce the incidence of postpartum anestrus (Palmer and Driancourt 1983).
Advantages for mating on foal heat include:
In the normal foaling mare, several events occur to the uterus in the immediate post-foaling period. This is termed uterine involution. Inflammation helps rid the uterus of debris and contaminants that are present in the uterus for the week after foaling. This process results in the formation of fluid, called lochia, which is often seen coming from the mare’s vulva. This fluid is usually reddish-brown and does not have a foul odor. The uterus, which is a strong muscle, actively contracts after foaling to help evacuate the fluid and debris. Contractions are also important for returning the uterus to its pre-foaling size. Suckling by the foal and exercise are important stimulants for uterine contractions and evacuation. Tissue repair and uterine “clean up” are essential for re-establishing pregnancy. Involution occurs rapidly after a normal parturition. Within 30 days of foaling, the uterus should have returned to its’ pre-foaling state in both tissue health and size.
Major factors thought to be related to fertility achieved on foal heat breeding include an uncomplicated birth free from genital tract trauma, prompt passage of the placenta, rapid uterine repair/involution, and early return to regular estrous cycles. Selection of mares for foal heat breeding should be based on meeting these minimum criteria to optimize success.
Strategies For Breeding Mares on Foal Heat
Breeding mares on foal heat is not a recipe-driven event. Each mare must be treated as an individual and the conditions of her foaling considered. In general, young mares with uncomplicated foaling are better candidates for breeding on foal heat than older mares that have previously delivered several foals.
A general approach to breeding mares on foal heat starts in the week after foaling. First, all mares should be examined no later than 6-8 days after foaling. A visual examination of the mare’s reproductive tract will reveal the presence of urine pooling, pneumovagina or unresolved trauma to the vagina, vestibule or vulva. Although these conditions usually will improve over time, injured mares are not good candidates for breeding on the first postpartum estrus. Examination of the internal reproductive tract using an ultrasound should be performed to reveal the presence of intrauterine fluid accumulation and size of any developing follicle(s). These factors are monitored by repeating examinations at 1-2 day intervals. If fluid is present in the uterus at the time when foal heat breeding is anticipated, it is better to treat the mare to remove the fluid than to breed the mare. Mares judged to be involuting normally, with no significant intrauterine fluid accumulation, are good candidates for foal heat breeding. If the mare ovulates prior to day 10 post partum, breeding on foal heat can be bypassed and prostaglandin can be administered 5-6 days after ovulation to induce an earlier return to estrus for breeding. It is thought that this protocol allows the uterine environment more time for repair, as well as provides a shorter interval (1-2 weeks) to breeding than that achieved by waiting for the second postpartum estrus to spontaneously occur (typically around day 30).
Some mares will accumulate fluid after the foal heat breeding. Such mares should be treated to remove fluid and resolve any infection that may have been established. Performing uterine lavage (3-5L lactated ringers or saline solution) in these mares is important, and is thought to not interfere with fertility if the lavage is performed at least 4 hours after breeding (Brinsko et al 1991). Use of drugs to promote uterine contraction, such as oxytocin, can also be helpful when treating mares with uterine fluid. Often, oxytocin is combined with uterine lavage for fluid removal in the breeding period. While the inclusion of antibiotic infusions after breeding postpartum mares remains controversial, some individuals (Pycock, 1994) have reported that postpartum mares treated with antibiotics plus oxytocin had higher pregnancy rates than either mares treated only with oxytocin or mares that were left untreated.
In conclusion, not all mares are suitable candidates for breeding during the first postpartum estrus. However, using careful selection of mares, breeding during foal heat can result in favorable pregnancy rates in a highly efficient manner, and can reduce parturition to conception interval to help to maintain yearly foal production in mares.
Dr. Margo Macpherson received her DVM degree in 1990 from Michigan State University after which she completed a residency and Master’s Degree in Equine Theriogenology at Texas A&M University. After leaving Texas, Dr. Macpherson spent time at the University of Pennsylvania and in private practice in Central Kentucky. Currently an Associate Professor and Service Chief in the section of Reproduction at the University of Florida, Dr. Macpherson is primarily interested in conditions that affect pregnancy including twin pregnancy and placentitis.
Blanchard, T.L. and Macperson M.L. 2011. Breeding Mares on Foal heat. Equine Reproduction, 2nd Edition, Editors: A.O. McKinnon, E.L. Squires, W.E. Vaala and D.D. Varner, Wiley-Blackwell, West Sussex, UK.
Brinsko, S.P., Varner, D.D., Blanchard, T.L. 1991. The effect of uterine lavage performed four hours post insemination on pregnancy rates in mares. Theriogenology 35:1111-1119.
Loy, R.G. 1980. Characteristics of post partum reproduction in the mare. Vet Clin N Amer: Large Anim Prac 2:345-359.
Palmer, E., Driancourt, M.A. 1983. Some interactions of season of foaling, photoperiod and ovarian activity in the equine. Livest Prod Sci 110:197-210.
Pycock, J. 1994. Assessment of oxytocin and intrauterine antibiotics on intrauterine fluid and pregnancy rates in mares. Proc Amer Assoc Eq Pract 40:19-20.
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