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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11 October 2015 THE HORSE TheHorse.com For additional news items, see TheHorse.com/News Social Communication and Equine Reproduction Domestic horses' reproductive effi- ciency is often lower than that of horses living in feral herds. In the latter case, stallions typically live with mares in harem bands, with other stallions in bachelor bands, or occasionally in mixed-sex transitional bands. Modern husbandry, breeding practices, and social structures of domesticated horses differ greatly from natural conditions. For instance, we tend to keep domestic stallions isolated from mares and other horses, with live matings taking place "in-hand" and semen collection carried out using a phantom (breeding mount) and artificial vagina. This modern management has resulted in a wide disparity between domestic horses' sexual behavior and that of their feral counterparts, for whom mate-choice systems have evolved in natural conditions. Find out what researchers recently learned about social communication's impact on reproductive success at TheHorse. com/36364. —Vincent Gerber, DVM, PhD, Dipl. ACVIM, ECEIM, WEVA Treasurer ? "Contrary to popular belief, the fact that there's greater contact surface with a Western saddle compared to an English saddle does not mean there's more uniform pressure distribution," said researcher Katja Geser-von Peinen, DVM, Even though pressure values in the Western saddles in Geser-von Peinen's recent study were particularly high, the horses showed no signs of saddle-related soreness or discomfort. So more research is necessary to understand what effect Western saddles actually have on the horse's back, she said. In the meantime, riders should realize that this kind of saddle isn't necessarily providing the even pressure distribution they might have expected, she added. WESTERN SADDLES DON'T DISTRIBUTE PRESSURE EVENLY ? W E S T E R N S A D D L E S D O N ' T DID YOU KNOW COURTESY PAINT HORSE JOURNAL Sedation and Lameness Exams It might be easy to tell when a horse is noticeably lame, but finding the source of his pain isn't always so simple. Veterinarians can use carefully placed diagnostic analgesia (commonly known as nerve blocks) to help localize a lameness to a certain area. However, administering the analgesia can be challenging, espe- cially in uncooperative horses. "To desensitize the nerves, a local an- esthetic is injected through a small needle around the nerve," explained Matthias Ret- tig, DVM, of the Free University of Berlin, in Germany. "Some horses … kick, which can be very dangerous for the veterinarian performing the block." A low dose of a sedative could help quiet a fractious horse, but previous research results suggest sedatives can have an analgesic effect and interfere with the lameness. So Rettig and colleagues set out to test the influence of a sedative (xylazine administered at 0.3 mg/kg of the animal's body weight) on 44 horses. "This was a small study, but gives us something we can work with," he said. The team used an objective body- mounted inertial sensor system to deter- mine whether the sedative impacted each horse's lameness, and they ultimately determined that the drug administered at 0.3 mg/kg had no significant effects on how the horses moved. Rettig cautioned, however, that doses should be chosen carefully, as too high a dose could skew results. "(A higher dose's) effect may not be as worrisome in a horse that is really lame (Grade 3 or 4 out of 5), but if you have a low-grade lameness (Grade 1 or 2), the xylazine might cause a change in the lameness pattern and influence the veterinarian's evaluation," he warned. Additionally, Rettig encouraged practi- tioners to use caution when working with difficult horses: "The veterinarian has to use common sense," he said. "If the horse is too dangerous and the veterinarian is putting him/herself or anybody involved at risk, I suggest other diagnostic modalities to evaluate the cause of lameness." —Katie Navarra Movement Asymmetry in Working Polo Ponies Evaluated Researchers have determined that polo ponies display a high degree of movement asymmetry, as compared to horses in other disciplines. Thilo Pfau, PhD, of the Royal Veterinary College, in England, and colleagues found that 60% to 67% of the 60 polo ponies they studied fell outside threshold limits for symmetrical movement. Pfau stressed, however, that, "very importantly, asymmetry in movement is not always caused by pain, which would then be clearly a lameness." Conformational issues could be a contributing factor to movement asymmetry, which, Pfau said, is a bit of a chicken-and-egg scenario: "Do differences in con- formation cause movement asymmetry, or do changes in movement and, hence, force between limbs lead to long-term changes in conformation?" Further, long-term studies are needed to find out how many of the horses that move asymmetrically are suffering from pain-related lameness, he said. Learn more at TheHorse.com/36201.—Katie Navarra Learn more at TheHorse.com/36238 ANNE M. EBERHARDT/THE HORSE ISTOCK.COM