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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18 TheHorse.com THE HORSE September 2015 soft tissue health is another story. Hansen says older horses tend to lose strength and tone in their muscles and tendons. Today we're riding and competing horses further into their golden years, so keeping their musculoskeletal systems fit for athletic ac- tivity is an important study area. Recently researchers have focused on an unusual tendon rupture that's more common in se- nior horses and a joint supplement that's trendy among senior horse owners. 1 Senior horses are at greater risk of superficial digital flexor tendon rupture Scientists at the University of Califor- nia, Davis, examined ultrasound images from 1,317 horses for evidence of damage to the superficial digital flexor tendon (SDFT), which runs down the back of the cannon bone over the deep digital flexor. They compared their findings to the horses' ages and activity levels. What they found There were only 14 actual SDFT ruptures, but all occurred in horses that were 15 to 30 years of age. Ten of the animals were retired or used for light riding, one was used as a breed- ing stallion, and three were still actively used in sport. About half the ruptures occurred during turnout. Injury caused acute severe pain and lameness, requiring strict stall rest for 14 to 90 days and lead- ing to pasture soundness at best. Why this study is important The mean age of the animals with SDFT rupture was 21.4 years, so this appears to be an age-specific injury. Owners of older horses need to be aware of the risk and observant for telltale signs, including "acute severe pain and lameness with swelling of the palmar carpus (on the back of the forelimb, near the knee) and/ or metacarpus (cannon bone)," says study author and associate professor Betsy Vaughan, DVM. 2 One joint supplement doesn't seem to help older horses Researchers at Utrecht University's De- partment of Equine Sciences, in the Neth- erlands, studied the ability of a combined glucosamine, chondroitin sulfate, and methylsulfonylmethane (MSM) supple- ment manufactured in Europe to improve gait stiffness in 24 horses, ages 25 to 34. They used kinematic gait analysis to evaluate each horse's walk and trot on a treadmill before and after treatment with the supplement or a placebo, looking at stride length, carpal flexion, forelimb fetlock extension, and tarsal (lower hock) range of motion. What they found Supplemented horses showed no improvement in any of the studied parameters. Surprisingly, though, carpal flexion and forelimb fetlock exten- sion in placebo-treated horses actually improved, possibly related to habituation to exercise, the researchers say. Why this study is important Owners continue to look for "natural" ways to improve their horses' health, and there are many product options marketed and purchased for this purpose. But add- ing supplements can upset the horse's dietary balance, Elzinga says. We know senior horses are at a greater risk of developing arthritis and other joint is- sues, Hansen adds, but that's no reason to add supplements to their diets that aren't proven to be effective. Future stud- ies would test other products' efficacy. The fact that this study's control group showed joint improvement is a good reminder that light exercise alone might help loosen up those old joints. Inflamm-aging Studies Perhaps the hottest area in senior equine research today is the field of "inflamm-aging." Horses and humans develop low-grade chronic inflamma- tion as they age, says Hansen. And that inflammation escalates with increasing body condition score—the older and more obese the horse, the more pro- inflammatory markers scientists find in the blood and in lung fluids (detected 6 Senior Horse Studies to Know Healthy senior horses can digest nutrients just as easily as younger horses. These results provide important evidence that age-related immune changes or 'dysfunctions' are organ- specific." DR. SANNI HANSEN