Reproduction and Sports Medicine Update: AAEP 2007
Ahhh, the Caribbean life ... toes in the sand, margarita in hand, and ocean water warm as a bath and clear as an aquamarine. Throw in a bunch of veterinarians and researchers discussing equine reproduction and lameness and what do you get? An event that combines continuing education with more than a little relaxation.
More than 170 equine practitioners from Florida met Sept. 27-29, 2007, at the Atlantis resort on Paradise Island, the Bahamas, for the third annual Florida Association of Equine Practitioners (FAEP) Promoting Excellence Symposium.
Veterinarians who attended presentations at the event came away with 18 hours of continuing education credit and new knowledge of current topics in equine reproduction and lameness.
"They got excellent speakers--probably the best they've ever had--and there's something for everybody," said attendee Anne Moretta, VMD, of Maroche Equine Clinic, who splits her practice time between Florida and Pennsylvania.
Many of the presenters encouraged dialogue, with speakers questioning attendees on what steps they would take to diagnose and manage horses presented as case studies.
Here are some of the highlights.
NECK PAIN IN SPORT HORSES
Sue Dyson, VetMB, PhD, FRCVS, head of Clinical Orthopaedics at the Animal Health Trust in Newmarket, England, used videos and case studies to discuss neck pain in sport horses.
She noted that neck pain can manifest itself through a wide variety of clinical signs, which can make correct diagnosis difficult. This pain can result from a number of factors, including trauma, muscle injury, fracture or displacement of a vertebra, or osteoarthritis.
Clinical signs of neck problems can include stiffness, muscle atrophy, patchy sweating, shortened forelimb stride, forelimb lameness, and abnormal head carriage.
The causes of this pain can include remodeling in the vertebrae or facets, loss of joint space due to disk problems, trauma to nerve roots, or primary soreness of the brachiocephalicus muscles (muscles that run from the bicep to the back of the skull and provide lateral flexion of the neck).
To find the source of the pain, Dyson said she considers the posture of the horse's head and neck, reaction to palpation and manipulation, and sensitivity at acupuncture points. She also assesses neck flexibility and watches the horse eating from the ground, and she observes the horse moving naturally on the longe and when ridden.
To assess neck flexibility, Dyson uses passive manipulation (in which the horse flexes itself, as with "carrot stretches," rather than being physically moved into a position), watches the horse turn small circles to the left and right, and watches the horse moving freely on the longe. She prefers to promote and watch free, spontaneous movement, as horses will brace against forced stretching.
"There are some horses that are naturally stiffer than others, and that may not be associated with any particular pain," she cautioned.
There are many different clinical manifestations of neck pathology. Careful clinical evaluation, correlated with imaging, is important for getting to the bottom of these cases.
The equine carpal (knee) joint is a veritable puzzle of bones and sometimes a diagnostic enigma for veterinarians. Mike Ross, DVM, Dipl. ACVS, of the University of Pennsylvania's New Bolton Center, offered some insight to practitioners on working up horses with carpal pain.
Ross showed case study videos to illustrate the telltale gait displayed by horses with problems in this region and explained his exam process. Some of the culprits causing pain in this region include chip fractures and sclerotic, remodeled bone.
While the horse's way of moving and heat in the joint can tell a practitioner that the knee is where a horse might be hurting, things can get a little tricky beyond that. Palpating the multifaceted, but unyielding, surface of the knee isn't likely to elucidate what's happening inside this complex structure. Nerve blocks and scintigraphy can be useful, but each have their own problems.
Pinpointing the carpal pain might only be the beginning of the exam for the affected horse: "Compensatory lameness is a huge problem, I think," Ross said. "They get lame in one leg, overload another leg, and become lame in that one."
ARTHROSCOPY: THE BETTER TO SEE YOU WITH
Utilizing an arthroscope--a slender instrument for visualizing the environment inside joints--can be a good move when radiographs fail to reveal the bony cause of a horse's lameness. Dean Richardson, DVM, Dipl. ACVS, head of surgery at the George D. Widener Hospital for Large Animals at the University of Pennsylvania's New Bolton Center, presented several case examples comparing radiographs and arthroscopic findings. Richardson had been in the headlines as the lead veterinarian for Kentucky Derby-winning Thoroughbred Barbaro, who was injured in the Preakness and eventually succumbed to laminitis.
Richardson compared radiographs and arthroscopic findings on each of several joints in his presentation. He noted that two joints with radiographs that look identical can be remarkably different on the inside.
"Radiographs are a two-dimensional representation of a three-dimensional structure," Richardson said. "When you're looking at radiographs, recognize their limitations."
In several of the case studies presented, the radiographs of the affected joints looked normal. But via arthroscopy, some of the final diagnoses on these same joints included meniscal (intra- articular cartilage or membrane) tears, damaged cartilage, chunks of cartilage floating freely within the joint, and osteochondrosis dissecans (OCD) lesions.
"When it comes to joint diagnostics, arthroscopy is still the gold standard," Richardson concluded.
ARTIFICIAL INSEMINATION: SITE OF DEPOSITION MATTERS
When it comes to artificial insemination, it might not be how much you have, but where you put it. Deep-horn insemination, which involves placing semen directly into the uterine horn containing the follicle, could allow breeders to use far less ejaculate per mare, maximizing stallion fertility rates, and reducing the likelihood of endometritis, according to Juan Samper, DVM, PhD, Dipl. ACT, a reproductive specialist and private practitioner in Langley, British Columbia, Canada.
Samper said reducing the number of sperm cells required per dose could:
- Increase the number of mares that could be bred per ejaculate;
- Maximize the effectiveness of sperm per dose (which is especially important in the case of a limited supply of semen, such as with stallions that have died, have been gelded, or have fertility problems);
- Increase the efficiency of sex-sorted sperm (since sex-sorted doses contain less sperm due to the removal of sperm that bear genetics for the undesired sex);
- Allow breeders to better utilize stallions with suboptimal ejaculate; and
- Reduce the likelihood of endometritis (inflammation of the innermost lining of the uterus) by reducing the amount of sperm--which can contribute to this inflammation--in the uterine environment.
In one study of deep-horn insemination, the researchers used 25 to 300 million sperm. Of the mares in the study, 73% became pregnant, with no correlation to the volume of ejaculate used.
Samper walked practitioners through two variations of the deep-horn insemination procedure.
Samper said these methods can help a veterinarian and a breeding operation to make a little semen go a long way, without increasing the risk of inflammation in the delicate uterine environment.
ATYPICAL CAUSES OF STALLION INFERTILITY
Dickson Varner, DVM, MS, Dipl. ACT, professor in the Department of Large Animal Medicine and Surgery at Texas A&M University, presented several cases of stallion infertility. These scenarios shed some light on some of the typical and atypical reasons for this expensive problem.
Some of the cases Varner illustrated included issues with the quality and quantity of sperm and problems with the stallion's reproductive conformation, including congenital abnormalities (those present at birth). He also discussed the impact of case history in assessing these horses. Varner looked for feedback on the cases from the assembled practitioners, quizzing the attendees on what steps they would take to diagnose and manage these stallions.
Varner noted that stallions get to remain intact and become sires because of their pedigree, conformation, and performance--not necessarily their reproductive ability. So it might be up to veterinarians to close the gaps to get them performing at their optimal level.
Some of the issues discussed during Varner's presentation included:
- Ampullae (the thickened distal portions of the deferent ducts, which are the secretory ducts of the testicles) that become plugged with sperm during the off-season,
- Sperm that do not develop pores between the surface membrane and underlying acrosomal membrane, thereby disallowing release of enzymes that are critical to penetrating the layers surrounding the egg,
- Problems with spermatogenesis related to overheating, as in the case of a horse recovering from an illness that resulted in him spending long periods of time lying down; and,
- Congenital abnormalities in a stallion's reproductive conformation.
AND THE LADIES ...
When examining the chronically infertile mare, it's important to remember that the uterus is not an organ suspended in space--it must be viewed as one part in a complex system. Anything affecting the animal, no matter how remote, can have an effect on the reproductive system, according to Michelle LeBlanc, DVM, Dipl. ACT, a practitioner with Rood & Riddle Equine Hospital in Lexington, Ky.
Diagnosing these mares begins with a physical exam of the entire animal.
"Your physical exam and taking a good history will give you the answer about 60% of the time," LeBlanc said.
The veterinarian should consider factors such as the mare's age, condition, and whether she's sound. If that checks out, then scrutinize the reproductive system more closely.
If she notes anything abnormal during the vaginal exam of the infertile mare, LeBlanc advocates running both cytology (examination of the cells) and cultures. In a recent study, LeBlanc and Tom Riddle, DVM (founding partner of Rood & Riddle Equine Hospital), looked at the diagnostics used on 970 Thoroughbred mares in Central Kentucky. Of these mares, 55% of those with reduced fertility would have remained undiagnosed without cytology to catch inflammation, and 17% would have remained undiagnosed without culture to catch infections.
In another study, LeBlanc looked at the results of 401 small-volume uterine flushes performed on 308 mares, correlating the clarity of the flushed fluid to laboratory findings. She found that cloudy fluid is highly indicative of the presence of bacteria, with Escherichia coli or b-Streptococcus being isolated most frequently. LeBlanc noted that practitioners using this technique increase their likelihood of finding bacteria in the uteri of chronically infertile mares by about twofold as compared to culture swab.
LeBlanc also uses endoscopy to visually inspect the reproductive system. In one case she reviewed, a mare had no inflammatory cells on cytology and no bacteria isolated from a swab culture, but the endoscopic exam revealed that she had adhesions throughout her uterus. Without this diagnostic modality the cause of her infertility could have remained unanswered.
Use of an endoscope might be indicated when the practitioner suspects adhesions, focal infections, foreign bodies, persistent endometrial cups, or when the cause for the infertility is unclear.
The diagnosis and treatment of chronically infertile mares is a complex process. Practitioners should utilize the available diagnostics, including cultures and cytology, along with endoscopy, to root out the myriad causes of this problem and increase the chances of these mares having a fertile future.
Along with the sun, veterinarians attending the FAEP Symposium soaked up a great amount of information on the latest in equine reproduction and lameness. While they might have missed out on the beach, horse owners and vets who couldn't attend can get up to speed by reading full coverage of the presentations from this meeting. Do a keyword search for "FAEP" on TheHorse.com to find the full text of these selections and more.
About the Author
Erin Ryder is a former news editor of The Horse: Your Guide To Equine Health Care. She owns a portly gray gelding named Duncan and dabbles in several equestrian disciplines, with an emphasis on dressage.
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