Dr. Charlie Scoggin was raised in Boulder, Colorado, but went to college at Colgate University in upstate New York to achieve his bachelor’s degree. He traveled back home to pursue his postgraduate and professional studies at Colorado State University, receiving a master’s degree in equine reproductive physiology in 2001 and his veterinary degree in 2005. Dr. Scoggin joined the team at Rood and Riddle Equine Hospital in 2015 as a fertility clinician following a 7-year stint as a resident veterinarian at a large Thoroughbred Farm in Central Kentucky. He is a Diplomate of the American College of Theriogenologists (animal reproduction).
Q - What is Theriogenology and what are the latest challenges seen in the stallion reproductive physiology in the 21st century?
A - Theriognology is the study of animal reproduction. In North America, theriogenologists are specialists that have undergone several years of formal and intensive post-graduate training in reproductive anatomy, physiology, pathology and endocrinology of a multitude of species, including mammals, avians and reptiles. As a theriogenologist, there are two great challenges that I commonly encounter with respect to stallion reproductive physiology: reliably predicting fertility; and maintaining adequate libido throughout the course of a breeding season.
Q - How would you define assisted reproductive technologies? And what are the processes/ procedures called into use?
A - Equine assisted reproductive technologies (eART) encompass those techniques that involve manipulative procedures of gametes (e.g., spermatozoa and oocytes) and embryos. These procedures are often employed to generate offspring from mares and stallions that are incapable of either creating or maintaining viable pregnancies. Some procedures, such as semen collection and artificial insemination, have been utilized for decades. Others, such as intracytoplasmic sperm injection (ICSI), are in their relative infancy yet gaining significant momentum in commercial breeding operations. The future of eART is also very bright. On the horizon are commercial embryo biopsying (to diagnose the sex, coat color, susceptibility to disease, performance traits, etc.) and a true in vitro fertilization.
It is important to note that the use of eART is not permissible under the current rules of the North American Jockey Club, which is the sole registry of Thoroughbreds in the USA. All Thoroughbred foals must be conceived via live-cover mating and the mare must carry that pregnancy to term.
Q - Is it much more common for Thoroughbred horses to be bred either ‘in-hand’ (that is, the stallion is led by a human), or using ARTs. Could you please tell us more about the process and challenges?
A - As mentioned above, Thoroughbred foals can only be registered if they were conceived via a live-cover (i.e., in-hand) mating and the dam carried the pregnancy to term. The use of eART is prohibited by the North American Jockey Club and, if I am not mistaken, all Thoroughbred registries throughout the world. Reinforcement matings—which entails collecting the drippings from a stallion as he dismounts a mare and depositing it back into that same mare’s uterus—is permissible, but it is not considered a true eART.
Q - What are your thoughts/professional opinion about the possibility of experienced frustration caused by preventing the animals from fulfilling behavioral needs through natural cover?
A - In my opinion and in general, the form of breeding contributes minimally to a stallion or mare becoming frustrated. However, what can lead to frustration—especially with respect to stallion behavior—is the frequency with which a stallion is bred. If he breeds too little, then he may become overly aggressive or anxious; if he breeds too much, he may become disinterested and shun the breeding process altogether. Fortunately, these issues can be mitigated by proper management and selection of an appropriate mare book size.
Q - Given the artificially limited season (by the studbooks) and the practice of ‘shuttling’ Thoroughbred stallions between Northern and Southern Hemispheres which has the potential to compromise their welfare by subjecting them to the stress of long flights, novel surroundings and unfamiliar pathogens, do stallions have infertility issues early in their stud career?
A - First and foremost, each stallion is an individual and should be treated as such. In other words, there is no “recipe” for how to manage a young stallion. For this reason, stallion managers and veterinarians need to take the time to get to know each stallion so that they can tailor their management strategies to best fit that particular stallion’s needs. Doing so often requires more than one examination or even more than one breeding season to really understand the personality and behavior of a stallion.With respect to shuttling stallions, all of the current scientific literature indicates that the shuttling of stallions between the two hemispheres has little to no effect on their fertility. A very recent study tracked the reproductive performance of stallions that shuttled over a 10-year period, and no significant differences were seen in first- and per-cycle pregnancy rates and live-foal rates. Unfortunately, there have been some publicized mishaps of shuttle stallions becoming sick or even dying, but those cases appear to be the exception and not the rule. The primary factor that can limit a stallion’s ability to shuttle successfully is libido. More studies are necessary to determine how shuttling effects libido both in the short- and long-term.
Q - How does use of a ‘dummy mare’ improve the welfare and extend the fertility of a stallion?
A - The use of a ‘dummy mare’ or ‘phantom’ mount is commonly used in breeds other than Thoroughbreds to collect semen for artificial insemination. The advantage to this method is that it can reduce the risk of injury to both the mare and stallion. Whether it be a kick, untimely move, or savage bite, the potential for injury during live-cover matings most certainly exists. The mare is a potential source of injury, whether it be from a kick, untimely move or falling over. However, frequency and severity of injuries in breeding stallions is not well documented and thus subject to some speculation. In my experience, injuries to stallions as a result of direct trauma from the mare are relatively uncommon. This is due in no small part to the intensity with which both broodmares and stallions are managed, which greatly reduces the risk of serious harm to a stallion during the breeding process.Regarding how the use of a phantom may extend the breeding career and fertility of a stallion: that is likely a secondary consequence of the ability to collect, process and inseminate mares in a variety of different ways than what live-cover affords. The use of frozen-thawed semen is an excellent example. Cryopreserved spermatozoa can essentially be kept in storage indefinitely. Indeed, there are some stallions that have been subfertile (or even dead) for years, yet the availability and use of their semen remains in circulation because of our ability to preserve and/or manipulate it in a variety of different ways.
Q - Please explain equine ART procedures in greater detail?
A - Artificial insemination (AI) entails the collection and processing of semen that allows for manual deposition of all or a portion of the stallion’s ejaculate into a mare(s) uterus. Embryo transfer (ET) involves the collection of an embryo from a donor mare’s uterus 6-8 days after ovulation and subsequent transfer of that embryo into a recipient (i.e., surrogate) mare’s uterus. The recipient will then carry the pregnancy to term and raise the foal as if it was her own. In horses, all steps of ET utilize non-surgical methods of collection and transfer. These particular procedures are used regularly in our practice.
Intracytoplasmic sperm injection (ICSI) involves collection of one or multiple oocytes (i.e., eggs) from a donor mare, followed by injection of a single spermatozoa under microscopic guidance into one of the oocytes. These “fertilized” eggs will be cultured for 6-8 days, after which they will be transferred in a similar manner as described for ET. The commercial use of ICSI has been available for ~10 years in the US and is considered a highly advanced form of ART. Currently, success rates of ICSI are relatively low and operate with poor efficiency. The current literature indicates that the odds of generating a live-foal from ICSI at around 10-25%, which is strikingly low compared to ET, which carries a live-foal rate of ~70-75%. In addition, ICSI is currently the only form of in vitro fertilization (IVF) that researchers have been able to generate pregnancies from. True IVF actually entails co-culture of sperm with an egg. Unlike humans or cattle in which IVF is capable of generating viable pregnancies, IVF has proven frustratingly difficult in horses. However, equine researchers are still actively pursuing the use of IVF in horses, and persistence usually pays off.
Q - What are the areas to be kept in-mind when an owner decides to breed his racehorse for the first time?
A - First and foremost, owners need to realize that mares and stallions are biologic entities and not machines. Despite intensive and proper management, per cycle pregnancy rates in horses average 60-70% on most well-managed Thoroughbred farms. So, while the odds are in favor of a mare becoming pregnant after her first breeding, there is also a chance that she may not. Fortunately, the odds are increasingly in their favor by the second mating, and seasonal pregnancy rates on most well-managed farms usually approach 90%. Along these same lines, it is important for owners to realize that just because a mare becomes pregnant doesn’t necessarily mean she will remain pregnant and produce a live and viable foal. The relatively long-gestational length of broodmares naturally increases the chances of an unfortunate event occurring, and—no matter how well cared for mares are—pregnancy wastage (i.e., fetal loss, abortions, stillbirths) will occur in a band of broodmares at a frequency rate of 10% per year. Bottom line: breeding horses is not an “automatic” process that guarantees the birth of a live and healthy foal.
Q - What challenges can a first time stallion face?
A - One of the biggest challenges is adjusting to a very different life than what they were accustomed to while in training and active competition. However, stud duty has its own demands, both physically and mentally. As such, new stallions should be given plenty of opportunity to “let down” following retirement from racing. This adjustment period can also be used by the stud grooms to also familiarize themselves with the stallion, allowing them to tailor management strategies to their new addition.Another challenge is offering reassurance via positive reinforcement for new stallions to express themselves in a natural yet respectful manner. Sometimes this takes a few days of training; other times, it can take weeks if not a whole breeding season to instill in a young stallion to breed with confidence. Young colts and even mature horses are often discouraged from displaying stallion-like behavior while in training for fear that it can distract them from reaching their full potential. Suppression of this behavior, while certainly understandable from both a performance and even safety standpoint, can have lasting effects once a stallion transitions into his second career as a breeding animal.
Q - How can breeders increase positive, welfare-maximizing factors?
A - The easiest way is to always try and put the horse first. Working for the Hancock Family’s Claiborne Farm instilled in me this principle. Remembering this dictum can make hard decisions a lot easier to make, and it symbolizes a commitment to the preserving the welfare of horse. Another means is for breeders to maintain an active role in the breeding process and educate themselves on current breeding techniques.
Rood & Riddle is a worldwide leader in equine healthcare offering innovative and highly skilled treatment of horses. Established in Lexington in 1982 as an ambulatory practice, Rood & Riddle became a full service equine hospital in 1986, serving as a referral center for horses requiring specialized medical and surgical care and providing ambulatory care for all breeds and disciplines. Rood & Riddle has recently expanded its Lexington, Ky location with the addition of a 208 acre reproduction facility. This addition, as well as satellite hospitals in Saratoga, NY and Wellington, FL, allows Rood & Riddle to uphold an unwavering commitment to quality, both in the care of horses and in relationships with clients and the community.