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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19 March 2018 THE HORSE TheHorse.com with his topline diving down in the middle. It's not unusual for these animals to appear this way in old age because they lose their topline very easily, says McLean. At the same time, they're getting a bigger belly that's pulling down on that topline, with gravity that "takes over with age." Then they've got a longer back and loin area compared to the underline, put- ting them at a greater risk than horses for weakness, she says. "Good exercise can help keep that topline from falling too much in seniors," McLean says. "We do side-to-side and under-the-leg exercises with carrots, and even lateral exercises like for a riding horse. Carrot exercises are so easy with donkeys because they respond very well to food." Eat Like a Donkey A donkey's metabolism just isn't made for the kinds of diets we feed horses and ponies. "Donkeys evolved from animals that survived on very little, in Africa and Asia, browsing a poor-quality, high-fiber diet more than grazing grass," Thiemann says. "And they've adapted well to that. Donkeys need one-third less calorie in- take than a pony of the same size. So they often need restricted grazing." They've also got a much longer gas- trointestinal transit time, McLean adds. "They can eat on Monday, and the food's still with them on Thursday or Friday." And because they have slightly differ- ent gut bacteria than horses, Thiemann says, their colons absorb more water from a very fibrous diet. To meet the particular needs of its aging donkeys and mules, The Donkey Sanctuary keeps them on a predominantly straw-based diet with mineral/vitamin supplements, rather than a hay-based diet. If their teeth are deteriorating, how- ever, they're at risk of impaction colic. "In that case, we move them onto a bedding of shavings and a diet that's pre-chopped but still low-calorie," Thiemann says. Warning: PPID and Laminitis An overfed donkey or mule is at high risk for developing metabolic issues—and that risk increases as they become older and more sedentary. "Laminitis is very common in donkeys, but by the time they show signs of it, it's often too late for management," McLean says. Unlike laminitic horses that shift their weight and have performance issues, affected donkeys simply lie down and remain fairly stoic, says Thiemann. "We'll often see quite advanced laminitis changes in our donkeys, with laminitic rings on the external hoof wall and with rotations and sinking of the pedal (coffin) bones," she says. Regular checkups by a professional farrier can help detect these issues, our sources say. So can a familiarity with the classic signs of pain in a donkey. Pituitary pars intermedia dysfunction (PPID, or equine Cushing's disease) is as common in mules and donkeys as it is in horses. But again, the warnings are far more difficult to detect. "The biggest signs are not shedding the hair coat and the fat deposits," McLean says. "But fat deposits are common even in healthy donkeys. In mules the fat deposits are go- ing to be more specific to PPID." The current PPID treatment for these animals is the same as for horses: pergolide. Unfortunately, however, the medication isn't perfectly adapted to long- eared equids. Donkeys and mules "don't like it," and it can make them go off their feed, Thiemann says, putting them at risk of secondary disease. "If a donkey goes off his feed, he's more likely to get hyperlipidemia (high fat levels in the blood) than a big horse," she says, which can cause lethargy, weakness, decreased water intake, and diarrhea. Exercise and Maintenance The last thing an old donkey or mule needs is solitude in a bare paddock. "An older donkey needs enrichment activities (that encourage movement) in the field or be taken on walks or continued to be exercised, even longed," McLean says. "It's important for their physical and their mental health." As they age, though, consider turning them out in flatter fields that are easier on old bones and joints, says Thiemann. As their sight deteriorates, make sure their environment stays the same and that they have a regular buddy. Finally, choose shavings over straw as bedding, which can allow mules and donkeys to rest more comfortably, reducing the number of times they have to lie down and get up. Aging donkeys and mules require plenty of TLC from their caretakers. "They need careful grooming, which is a time when owners can check for tumors, lice, and discharge from the eyes—all of which they're susceptible to as their immune systems start to run down," Thiemann says. While donkeys aren't very Old Stone Face The recently developed horse grimace scale (HGS) provides us with information about detecting signs of discomfort in our horses' faces. But subsequent research revealed that information doesn't apply to donkeys and mules. They're far more stoic, researchers agree. And they've also got thicker facial hair that hides expressions you'd see more easily on a Thoroughbred, for instance. "And it's not just the face; it's the whole-body posture," says Amy McLean, PhD, equine lecturer at the University of California, Davis. "I once saw a donkey suffering from peritonitis (inflammation of the abdominal lining)—which is really painful. I have three days of video of her face, but it never really changed aside from a little more blinking and opening of the nostrils." Donkeys are also unlikely to stop eating or drinking until they're in the worst stages of an illness, she says. Research teams at Utrecht University, in the Netherlands, are currently working on a grimace scale for donkeys, which will help owners and professionals avoid missing a health condition simply because the donkey didn't "act sick or painful," says Alex Thiemann, MA, VetMB, Cert EP, MRCVS, veterinary surgeon at The Donkey Sanctuary. As for mules, the fact that they're more closely related to horses doesn't give them an advantage. "They're very robust and probably even worse at showing pain behavior than donkeys," says Thiemann.—Christa Lesté-Lasserre, MA An older donkey needs enrichment activ- ities … It's important for their physical and their mental health." DR. AMY MCLEAN