A morbid activity of the kidneys, resulting in an excessive secretion of urine.
Diabetes assumes two forms, distinguished as diabetes mellitus and diabetes insipidus. The former is characterized by the presence of sugar in the urine, and an increase in the specific gravity. In the latter there is an absence of sugar, and the specific gravity is usually below the normal standard. Diabetes mellitus is rarely seen in the horse.
Profuse staling, or polyuria, is sometimes associated with indigestion and suppressed skin function. Hay that has been badly harvested, and by excessive fermentation become heated and " mowburnt", is one of the most frequent causes of the disorder, while in other cases the drinking water may be at fault. Foreign oats and hay are more frequently found to affect the urinary organs of horses in these islands than those grown at home. Debility and exposure to great vicissitudes of climate are also considered as a probable cause. The disorder is usually found to exist without any organic disease of the kidneys themselves.
In addition to the excessive quantity and the frequency with which the urine is passed, marked thirst is a prominent and lasting symptom. The pulse is weak, the skin loses its gloss, becomes dirty and closely "bound" to the parts beneath. The membranes of the eyes and nose are pale in colour, the appetite capricious, and the breath sour-smelling. The affected animal rapidly loses condition, and sweats under comparatively slight exertion. Moreover, the capacity for work is largely curtailed. The urine, besides being light in colour, has a low specific gravity.
In the early stage, and before excessive debility is present, a mild aloetic aperient may be given as a preliminary measure, and this should be followed by a demulcent diet, consisting largely of linseed tea, with scalded oats of the best description, and good sound bran. The so-called diuretic remedies should in no case be prescribed. Gallic acid or powdered nutgalls, with nux vomica and quinine, may be recommended. This failing, a course of iodide of iron should next be tried, and upon an abatement of the symptoms may be advantageously replaced by a mixture of nitro-hydrochloric acid and infusion of calumba. Belladonna, in the form of extract or tincture, is recommended in cases of some standing. The food should be of the best, and an unlimited quantity of drinking water allowed. The patient will be benefited by a short period of walking exercise in the middle of the day. On no account should he be exposed to wet, or to cold easterly or north-easterly winds. A warm but well-ventilated stable should be provided, and the surface circulation maintained by ample clothing. With proper treatment a few weeks suffice to bring about complete convalescence.