The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.
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SPONSORED BY A13 TheHorse.com/AAEP2017 March 2018 THE HORSE AAEP Wrap-Up artery with one lever, then makes the final cut for testis removal. The Serra crushes the artery and removes the testis at once. The researchers tested the methods on two groups of 40 equine cadavers—one group using an open technique (incising the parietal tunic, or the sac surrounding the testis) and the other using a closed technique (removing the parietal tunic with the testis). Then they further split the groups, castrating half using the Serra and half using the Reimer emasculators. The team found few differences be- tween the groups. Leaking pressure was higher (less likely to bleed after castration) in the open group with the Reimer, she said, and within the Reimer group, it was higher for open than closed castration. But ultimately, Santschi said, "either emasculator works fine." Navicular Bursotomy Outcomes Horses with septic or contaminated navicular bursae typically face a long and uncertain road to recovery. Even with sur- gical intervention, prognosis is typically guarded. To try to improve outcomes, a research team added regional limb perfusion (RLP) to the equation. Santschi shared the results of their study of 19 horses that were at least lame at the walk. Horses underwent a navicular bur- sotomy, in which the surgeon opened the bursa through the bottom of the hoof and lavaged the affected area with sterile fluid, in combination with RLP, which delivers high levels of drugs to leg tissues below a tourniquet, and systemic antimicrobials. Santschi said horses underwent two to three more RLP treatments and therapeu- tic shoeing at the surgeon's discretion. All horses survived. Sixteen returned to their previous use, and three became pasture-sound. The team reported that all 19 horse owners were satisfied with the outcomes and deduced that bursotomy in combination with systemic and local an- timicrobials is an effective treatment for septic or contaminated navicular bursas. Mepivacaine vs. Lidocaine in Blocks Vets perform palmar digital nerve blocks (PDNBs) to numb the hoof's rear portion for diagnostic and treatment purposes. PDNBs must last long enough for them to gather the information they're seeking. Santschi shared the results of a study in which researchers tested the du- ration of action of two local anesthetics— mepivacaine and lidocaine—on eight horses with induced forelimb lameness. They found that: ■ Mepivacaine resolved lameness in eight; ■ Lidocaine resolved lameness in three; ■ Both resulted in skin desensitization in all horses, but it happened sooner than lameness resolution after mepivacaine administration; and ■ Lameness resolution and skin sensitiv- ity lasted longer with mepivacaine. The researchers concluded that "mepi- vacaine is superior, with a reliable onset and longer duration of action." Joint Lesion Heritability, Prevalence When potential buyers are perusing survey radiographs of yearlings they're interested in purchasing at a sale, osteo- chondral lesions aren't an uncommon finding. But just how common are they in Thoroughbreds, and are they hereditary? In a retrospective study scientists re- viewed 34 radiographs from each of 1,962 Thoroughbred yearlings in Australia. They identified osteochondral lesions and analyzed the horses' pedigrees to estimate heritability. Their key findings included: ■ 23% of yearlings had at least one lesion; ■ Lesions were found in 10% of stifle, 8% of fetlock, and 6% of hock joints; ■ Overall heritability ranged from 0% to about 20%, with an average of 8%; and ■ Heritability was 16% for stifle lesions, 2% for fetlock, and 0% for hock. Santschi cautioned that while this study revealed a "modest" genetic component, prior studies have shown a higher degree of hock lesion heritability. Because there is a tendency to label all orthopedic inju- ries in young horses as osteochondrosis, and some are likely caused by trauma, she believes the veterinary community needs a better definition of osteochondral lesions. Subchondral Bone Cysts & Stresses Santschi et al. examined how subchon- dral bone cysts (subchondral lucencies, or SCLs, a common finding in radiographs at public auction) in the stifle's medial femo- ral condyle impact local bone stresses. They ran a CT scan on a yearling, then designed a 3-D model in which they could "create" cysts and "load" the joint to see how it reacts to different degrees of stress. The team found significant differences in tension and shear stress (in which the structure's shape deforms) throughout cyst development, which could lead to fur- ther bone damage and cyst enlargement. "These data provide a first step in un- derstanding the altered mechanics of sub- chondral bone surrounding a SCL," they said. "Additional studies may provide the basis for improved treatment strategies for SCL in young horses and may improve the understanding of SCL in humans." PRP to Treat Endometritis A group in Brazil studied the effects of administering intrauterine platelet-rich plasma (PRP, which has anti-inflamma- tory properties) on uterine inflammation (endometritis) and conception rates in mares with persistent-mating induced endometritis (PMIE). Mares with PMIE have lowered chances of conception. The team evaluated 13 mares with his- tories of PMIE bred via artificial insemina- tion (AI) once over each of three estrous cycles. During the control cycle mares received no treatment. In the second cycle they infused mares with PRP 24 hours prior to AI, and in the third, they infused with PRP four hours after AI. "There was a significant decrease in markers of inflammation in both treated cycles compared to the control cycles," said Turner. "Similarly, on histology (microscopic evaluation) and biopsy there was a significant decrease in evidence of endometritis in PRP-treated mares." To see if this meant improved fertility, the team determined pregnancy rates 14 days post-ovulation on each cycle. Control COURTESY DR. ERIC MUELLER Both the Serra (pictured) and the Reimer emas- culators are effective for equine castration. (Continued on page A16)