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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17 You're also likely eager for fresh infor- mation on how to care for your equids over 20, hoping they will live as long as possible but with a good quality of life. Researchers are responding to the call, focusing on aging equines' particularities—metabolic and hormonal issues, tendon and muscle weaknesses, feeding and exercise regimens, and lung and airway diseases, to name a few. So what's new and exciting in senior horse research? We turned to the individuals actively studying these horses to find out, and we've compiled a list of important senior horse studies conducted over the past year. The studies fall into three major categories: metabolic and endocrine dis- orders, soft tissue injuries, and probably the fastest-growing field of the relevent topics—"inflamm-aging." Amanda Ad- ams, PhD, of the University of Kentucky Gluck Equine Research Center, in Lex- ington, coined this term to describe the phenomenon of age-related inflammation throughout the body. Commenting on the studies are equine researchers Sarah Elzinga, a PhD can- didate at Gluck under Adams' direction, and Sanni Hansen, DVM, PhD, from the University of Copenhagen's Department of Large Animal Sciences, in Tåstrup, Denmark. Metabolic and Endocrine Disorder Studies Older horses are far more prone to developing metabolic conditions such as equine Cushing's disease (also known as pituitary pars intermedia dysfunction, or PPID) than their younger counterparts, says Elzinga. As many as 20% of senior horses suffer from PPID, which can set off a long chain of other health problems. These horses can also suffer from hyper- insulinemia (when blood insulin concen- trations rise above normal range), but whether it's a sign or side effect of PPID is still unknown. Because diet is the primary manage- ment tool for these diseases, researchers have been studying senior horse digestion and the role of a particular hormone in aging horses. 1 Senior horses digest just as well as younger adult horses Researchers at Michigan State Univer- sity, in East Lansing, and the WALTHAM Center for Pet Nutrition, in Leicester- shire, U.K., evaluated how healthy stock- breed mares of varying ages digested nutrients. Each horse consumed one of three different diets over a six-week period, and the scientists investigated a large range of digestion parameters. What they found Unlike humans, most horses maintain their ability to properly digest nutrients deep into their senior years. Why this study is important Many owners find feeding older horses chal- lenging, especially those that tend to lose or gain weight too easily. Understanding digestibility in senior equids can help us establish a proper diet for this population. "A lot of older horses have compound- ing problems that might mean they need some changes in diet," says Elzinga, who was the lead researcher on this study. "But if they're healthy, they can just keep eating whatever other adult horses are eating." 2 Serum insulinlike growth factor 1 does not decrease in old horses Scientists at the University of Co- penhagen, in Denmark, looked at how serum insulinlike growth factor 1 (IGF-1) evolves in aging horses. In humans and horses, previous studies have suggested that senior populations produce this growth-promoting hormone at lower rates than do younger populations. Re- searchers have considered the decrease a trigger for aging because older individu- als have stopped growing and certain soft and bony tissues aren't being renewed. To test the theory, Hansen and her colleagues compared IGF-1 values in 72 healthy horses, ages 5 to 27. What they found Their study results showed that IGF-1 levels don't drop in older horses. They stay essentially the same from age 9 on. Why this study is important This revo- lutionary finding reverses a previously held belief about what triggers aging in horses. By eliminating IGF-1 as a factor, researchers can now refocus their efforts on other triggers to try to slow aging's effects, says Hansen. If the results had indicated IGF-1 did trigger aging, they would have tried to find ways to either prevent it from dropping or boost it. Soft Tissue Injury Studies Horses seem to maintain bone strength and density even into old age, but their PAULA DA SILVA PHOTOS