Horses and the Drinking Issue

Another condition common among horses, humans and dogs is Cushing’s disease. It is usually caused by a tumor on the pituitary gland and is also referred to as pituitary dependent hypoadrenocorticism. In horses the signs of this condition include long, shaggy, wavy coats that do not shed during the summer; excessive thirst along with excessive urination; high blood-sugar levels; bulging eyes and a pot bellied appearance while having muscle loss in the back. Older horses and mares are most likely to get this disease.

In horses there are currently two treatment options. One is bromocriptine which is a dopamine-like drug and the other is cyproheptadine which is a seratonin-suppressing drug. On treatment, horses can survive up to several years although neither drug fights the tumor; rather they just control the symptoms. The horses condition will worsen gradually as the tumor inevitably continue to grow so euthanasia will eventually have to be considered.

Another condition that can result from a tumor in the pituitary gland is diabetes mellitus. This is not a common condition and the high blood-sugar levels are often mistake for Cushing’s disease. In fat ponies and miniature horses diabetes is more common. The condition is usually treated with insulin injections.

Another cause of excessive drinking can be renal failure. A urine sample will help your veterinarian determine if your horse has impaired renal tubule function which is the most common cause if the kidneys are involved. A preceding illness can cause renal failure if it affects the blood supply to the kidneys. Certain antibiotics or anti-inflammatory drugs can also be the cause if they are toxic to the kidneys.

Psychogenic polydipsia is another common cause of excessive urination. Some horses drink a lot of water for some unknown reason before being passed through healthy kidneys and resulting in an excessive amount of urine. These horses do not show signs of other diseases and are in good health. They will also have a good appetite while being capable of strenuous exercise. Only after you have eliminated all possible causes of excessive thirst should you start rationing their water. A horse can sometimes develop a urinary problem if they are treated for unrelated illnesses.

A course of fluid therapy to correct a problem or for supportive therapy for an acute disease can also lead to polyuria or the excessive passing of urine. Horses will often exhibit polyuria if they are on a corticosteroid therapy such as dexamethasone. As an after effect to tranquilization with sedatives such as xylazine or detomidine horses may have polyuria. Damage to the tubules of the kidneys can be inadvertently caused by certain antibiotics and polyuria can result, especially with the overuse of non-steroidal anti-inflammatory drugs of NSAIDs as painkillers.

It is rare for horses to get diabetes incipidus. It is characterized by the production of dilute urine and is caused by a hormone imbalance. After having water withheld horses with this condition fail to concentrate their urine. A hormone replacement can be used to treat this condition. The amount of urine a horse produces is affected by their diet. Horses will pass twice as much urine on a pelleted feed or legume hay compared to those on regular grass hay. Foals will also produce the same amount of urine as an adult horse.

Even though disease may not be the cause of polyuria/polydipsia it is still important to have a veterinarian check a horse before you apply any remedy. Several preliminary urine samples will be taken by your vet along with an examine of the horse, then they will likely ask you to give the horse measured amounts of water. A horse is probably experiencing polydipsia if they are drinking in excess of ten gallons of water a day.