The older horses get, the more likely they are to develop pituitary pars intermedia dysfunction (PPID). Not all will, of course. And good general management—proper nutrition, parasite control and other basic horse care—can help preserve a horse’s general health as the years pass. But when it comes to PPID, there’s one vitamin, in particular, that is crucial to decreasing risk: Vitamin E.
The reason? Vitamin E has antioxidant properties and PPID is the result of oxidative damage to the brain. “What starts it all is oxidative injury to the brain. Nerve cells from the hypothalamus send signals to the pars intermedia. Oxidative injury kills those nerve cells off, and when that happens the cells in the pars intermedia are no longer inhibited and they begin secreting too much hormone. If we can minimize oxidative injury, this would help,” explains Janice E. Kritchevsky, VMD, MS, is a professor at Purdue who has been studying PPID in horses for many years.
One of the world’s leading experts on PPID Nicholas Frank, DVM, PhD, DACVIM, of Tufts University, agrees that oxidative injury may be a key consideration in prevention of PPID. “Regarding why it develops in some animals—in addition to the genetics—since it is oxidative damage, we sometimes wonder if these animals have not received as many antioxidants through their life,” he says.
“Providing adequate vitamin E in the diet is a recommendation for all horses and may be particularly important if we want to try to decrease risk of PPID,” Frank says. “We recommend that all horses receive this vitamin in a multivitamin supplement, and in older horses we recommend providing additional vitamin E as a specific supplement. We always suggest vitamin E if we are trying to lower the risk of PPID. There are no studies saying it prevents PPID from occurring, but it may help, and certainly does no harm,” he says.
Sources of vitamin E
Horses naturally get vitamin E from grass and green forage. If they are on pasture for much of the year, this would supply all they need. “If they can’t be on pasture for various reasons, such as equine metabolic syndrome and an associated predisposition to grass founder, a vitamin E supplementation is definitely recommended. Those are factors we can do something about, but even keeping a horse on a vitamin E supplement his whole life does not stop PPID from happening. There are still the genetic influences that lead to some horses developing it,” he explains.
Good care, good feed and preventive care are best management practices, agrees Kritchevsky, but even with those in place a horse who lives long enough may still develop PPID. “In a way, PPID is a good problem to have because it means that your horse has lived to an old age,” she says.
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