Ask Horse Journal: 04/99

Anhydrosis: Your Horse Can’t Sweat
Last summer, my mare stopped sweating for the first time in her life. We found that a product called One AC helped her significantly. I am wondering if other vitamin C supplements would have a similar effect in terms of helping her to sweat.

-Jan Robbins

Anhydrosis means “no sweat.” Without the ability to sweat, the horse can easily develop life-threatening heat stroke. Anhydrosis is typically a problem of horses that are suddenly shipped to hot, humid climates from cooler regions and asked to perform before they have had a chance to acclimate to the heat, but it can occur in horses that have lived in such climates all their lives.

One theory of cause you sometimes hear is “exhaustion” of the sweat glands. However, skin biopsies show the glands are normal. Severe electrolyte deficiencies have been suggested as a possible cause (especially potassium) but, while these could certainly contribute and may be a result, they are unlikely to be the primary cause. Anhydrosis is found in people with disease of this portion of the nervous system. The problem may be in the brain, or the peripheral parts of the body, or both.

Skin testing of horses with anhydrosis using the hormone epinephrine (adrenaline) shows these horses are not as sensitive to epinephrine as normal horses. There are also reports that circulating levels of epinephrine are above normal in these horses.

Stress plays a central role in causing anhydrosis — the stress of extreme heat with or without other stresses, such as shipping and performance. No single treatment will help all horses with anhydrosis. Correction of electrolyte abnormalities (based on blood test results) should be done with supplementation appropriate to the climate, but over supplementation is not likely to be helpful or necessary since the horse that is not sweating is not losing electrolytes.

As you noted, vitamin C has been helpful in some horses. This is not surprising since vitamin C plays a critical role in the function of the adrenal gland — the “stress gland.”

There are also reports of horses who have resumed sweating after having chiropractic manipulations of their cervical spines. This sounds farfetched until you realize that the central nerves of the autonomic nervous system, as well as a series of control centers, run in close proximity to the vertebrae. People with problems in the vertebrae of the neck may develop abnormal sweating patterns. Manipulations may either release pressure on these structures or stimulate them — in effect jump starting the sweating mechanism.

Choline (a B vitamin) deficiency has been suggested as a possible cause of anhydrosis in other species. Choline is needed to manufacture the important neurotransmitter acetylcholine, the chemical that is released at nerve endings and stimulates receptor sites on tissues such as muscle and sweat glands. Acetylcholine deficiency has been implicated in anhydrosis. The horse gets an abundant supply of choline from whole grains in the diet. However, given the extreme stress these horses are under it is not a bad idea to supplement with B vitamins, including choline.

Complete rest and keeping the horse cool using protective housing and fans are important parts of treatment. Some horses never recover their ability to sweat. Others regain sweating but in some cases are never “the same,” according to owners.


Spoiled, Aggressive Horse
The first time I rode my 12-year-old gelding, he struck me as a green off-the-track Thoroughbred. Once I got to know him I realized he had major problems. He is dominant and aggressive. I have seen him chase people in the pasture, rear and strike out, run up to and kick at people, not to mention the usual broken cross ties and halters, head butts, biting, etc. I have never seen him be aggressive toward other horses. His riding had consisted of harsher and harsher bits with more and more bolting and bucking. He is a talented jumper — he used to jump the 5 ??-foot pasture gate from an easy trot. But under saddle his jumping is dangerous at best. I bought him because I felt it would either be me or the auction. (I know, I need my head examined.)

Three years later he is showing at training-level dressage and has impeccable ground manners. Under saddle, he is hot but obedient and willing — 90% of the time. Once in a while he reverts to his old ways. I can’t pinpoint what sets him off except that usually I’m not around when he loses it.

I have been his main handler. He gets a lot of praise and attention, and when I have to discipline him I use the same tactics the dominant mare would use — hitting on the shoulder and staring him down until he looks away usually gets the point across. He is turned out on pasture for eight to 10 hours a day with my two younger geldings, I ride him in a loose-ring French snaffle every day weather permits with either a trail ride or a day off per week. He gets bermuda hay free choice and two pounds of grain (milled locally with almost no molasses) morning and night.

What is the prognosis for a horse like this’ Am I ever going to be able to leave him in the care of someone else without fearing for their lives’ I can send him to a professional’s barn if I’m gone, but he won’t eat away from home. Am I ever going to be able to take him to a show and not have nightmares about him possibly getting loose and trying to kill someone’ Selling him is out of the question, in part, because he’s so attached to me (and me to him) and in part because I couldn’t do that to someone and still have a clear conscience.

-M. Mason

By the time you purchased this horse, you had definitely bought someone else’s problem, despite the progress you’ve made. We’re glad you threw away the harsher bits idea. This horse needs discipline, not devices. Don’t give him an inch. He obviously wasn’t handled much, and he didn’t learned to respect his handler, and he’s definitely spoiled.

On the ground, we would handle him in a chain shank and use it properly. Rearing, biting and striking cannot be tolerated, and you must be consistent in your handling. He needs more than a stare-down or hit on the shoulder. If possible, take this horse to a knowledgeable professional. If the horse misbehaves, pay strict attention to the trainer’s suggestions.

Frankly, you need professional help, even if it means boarding him (I wouldn’t be concerned about him not eating; that’s another tantrum. He’s not going to starve himself).

I also suspect that trying another handler may be a good idea, if you can find someone experienced enough to work with him, to see if the horse tries the same tactics. Try to work this horse in the heat of the day to take some of the edge off, and be consistent in your ground discipline.

You’ve got a spoiled horse who can be dangerous, as you are aware. Yes, you may be able to make him into a show horse, but you’ve still got a long road ahead with lots of fundamentals and consistent, firm discipline.


Rogaine For Horses’
When I purchased my 12-year-old Arabian-Saddlebred mare six months ago, I was told she had dew fungus but that it would go away in the spring. It’s worse. She is a bay with a blaze and about halfway down the blaze she has lost all her hair, leaving bare pink skin. I have tried everything from bacon grease to vitamin E cream but nothing seems to help. If I put nothing on at all, the area becomes crusty and cracked.

-Kimberly Smith
Madison, TN

“Dew fungus” is a general term used to describe skin problems on the nose/muzzle that are believed to originate from a fungal infection but could be caused by some irritant. It is a relatively minor condition that can be treated by local skin care (medicate d shampoos and creams) and not turning the horse out to graze on wet grass. However, it sounds like you may have a more serious problem.

A persistent fungal infection could explain the problem, but obviously it is not going to respond to simple measures. Get your veterinarian to do a culture of the area, looking for pathogenic fungi. If present, you will likely need either a prescription fungal shampoo and/or cream, such as Nizoral, or could try over-the-counter athlete’s-foot creams to treat her.

The problem could also be photosensitization, which is an abnormal sensitivity to sunlight. This can be caused by an underlying liver disorder or may simply be a problem your particular horse has. If fungal infection is ruled out, ask your veterinarian to do a complete blood chemistry to rule out liver disease. Certain weeds/plants may be at the root of such a problem. If there is no underlying organ disease, you will need to use sun block with a high SPF (sun protection factor), like those sold for use on human babies and children. Some fly sprays and coat polishes also include a sun screen.

Problems like yours may also be caused by an “autoimmune” disease, but rarely. There have been several described in horses similar to this one. Basically, the horse has antibodies to its own skin, and the skin that is under attack becomes more sensitive to things such as sunlight. In some conditions, you may also find tiny ulcers or vesicles (fluid-filled skin lesions, like blisters) along the coronary bands.

This problem can be diagnosed by doing a small skin biopsy. If you rule out infection, and sun screens don’t solve the problem, we recommend you locate a veterinary dermatologist and have the skin biopsy done. Corticosteroid skin creams may help this problem.

Another rare cause of such problems is skin cancer. However, this wouldn’t respond to creams and is not likely in your case. In any event, the skin biopsy would confirm or rule out that possibility.

Once the problem has been diagnosed properly and controlled, you may be able to use EQyss Mega-Tek Cell Rebuilder (800/526-7469) to encourage hair regrowth (see April 1997 page 22). However, be certain to check this out with your dermatologist or treating veterinarian first to make sure it can be used with your other primary medications.


Sharing Boots And Brushes’ Sometimes Not
Boots, wraps and sheets that will be left on for any prolonged amount of time should be washed between horses. Each horse carries a slightly different bacteria and other organisms on his skin. An array of organisms that is harmless to one horse may prove disastrous to another when allowed to grow in the warm, moist environment under a wrap. This is particularly a problem with neoprene and synthetics that do not “breathe,” such as most water-resistant materials. Deep skin infections may develop even if there is no obvious break in the skin. This is sometimes blamed on a reaction to the material when the real cause was failure to wash wraps between horses.

Everyone knows “grunge” skin problems can spread from horse to horse. Be vigilant about not using equipment from affected horses on any other animal. This includes grooming tools, saddle pads, towels and blankets. Even your hands can spread infection, so wash your hands before moving on to the next horse.

An often overlooked source of spread is in the wash stall. Sponges harbor bacteria and fungi. Use new sponges and soft brushes to wash affected horses. Never leave water sitting in the bucket when you are finished. Almost all shampoos, including medicated ones, are less than 100% effective in killing organisms, and these will multiply in the dirty water.

An effective, inexpensive disinfectant is Clorox. Follow label directions for disinfecting brushes, sponges (not natural sponges, however, which need to be boiled) and other grooming equipment. Use a 1/4 to 1/2 cup full strength to disinfect buckets after use. Drying equipment in the sun gives added antimicrobial benefit.


NSAIDs and Joint Disease
Cortisone is avoided in many cases of joint disease because of its capacity to inhibit cartilage formation under certain circumstances (long-term use, high doses). However, the alternative, NSAIDs (nonsteroidal anti-inflammatory drugs), may do the same thing.

Aspirin, ibuprofen, indomethacin, naproxen and phenylbutazone have all been shown experimentally to inhibit synthesis of proteoglycans (the long chain sugars with amino acids attached that are the backbone of connective tissue and joint cartilage) under some circumstances. The steroid prednisolone and the NSAID flunixine (Banamine) have shown no effect on proteoglycans under laboratory conditions. The ideal NSAID for use in joint disease appears to be the experimental drug carprofen, which can actually stimulate proteoglycan synthesis. Carprofen has not yet been cleared for use in the United States, but it is widely used in other countries. Until we have access to such a safe NSAID, the best rule is still to limit use of steroids and anti-inflammatories to as little and as infrequently as possible. Regular use may make arthritis worse.


Simple Leg-Wound Bandage
Draining/infected wounds on the lower leg can be a challenge to bandage. Seepage to the outer protective layers requires frequent bandage changes, as it can serve as a culture medium for bacteria and a “wick” that directs them right to the wound. Gauze pads often do not have enough absorbency, so are no help. A good solution is to use a sanitary napkin directly against the draining area. Medications can be applied to the wound itself and/or the contact surface of the pad. The high absorbency of these materials and plastic outer surface will draw the wound drainage to the interior and keep it there, away from the rest of the wrap. Contact surfaces will not adhere to skin and wound, unless you leave the bandage on too long and the surface becomes completely dried out.

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