Diarrhoea is the expression of an irritable condition of the alimentary canal, sometimes resulting from an excess, or deficiency or impaired quality of one or other of the digestive secretions. It is marked by an increase in the quantity and fluidity of the alvine discharges, and is accompanied by digestive disturbance, and occasionally by inflammatory changes involving the stomach and bowels.
The causes that give rise to diarrhoea are improper food, sudden changes from one kind to another, gluttony, eating too fast after long abstinence, imperfect mastication, bad water, chills, overwork, and exposure to vicissitudes of climate. It may also be induced by parasites, chemical irritants, and injudicious drugging, or perverted function of the liver and other organs. Besides these, excessive action of the bowels may be caused by an effort of nature to rid the system of some deleterious agent in the blood. This is not unfrequently seen in advanced lung disease, or where the function of skin or kidney is arrested and impurities which they should discharge are allowed to accumulate in the system. When associated with other diseases, and as a sequel to inflammatory and wasting disorders, it is a grave condition, and may be the prelude to dissolution; the conditions which bring about like results in the young have often a very different origin and more frequently fatal consequences. In some seasons and in particular situations a mucous catarrh, extending from the mouth to the anus, and especially involving the bowels in certain portions, is sometimes prevalent among foals. Its cause in the majority of instances is some alteration in the character of the milk, or functional derangement of the mare, consequent upon unsuitable food, or it may be a sequel of difficult labour, or parturition troubles. Anything interfering with the well-being of the dam is liable to be reflected in the health of the sucker. A very large proportion of the cases of diarrhoea met with in young foals are to be accounted for by long abstinence while the mares are at work, and the overheating and excessive exertion to which the latter are subjected at a time when nature is making a special demand on the system in the supply of milk. Maternal solicitude under certain circumstances renders mares restless and excitable, and takes more out of them than the work assigned would do at any other time. Without discussing here the propriety or otherwise of working mares while suckling, we may remind readers unacquainted with the details of farming, that foals arrive at a time of the year when the majority of agriculturists have much need of the mare's services, and economic considerations demand that notwithstanding her maternal duties she must contribute to the general work of the farm. The practice of hand-milking the dam on return from work while she is allowed to fondle her foal over a gate till their mutual excitement has subsided, would appear to reduce the liability to derangement of the foal to some extent, and no serious objection can be made to it; the foal will get a sufficient supply after the more objectionable portion has been drawn off, and possibly that portion which would have proved deleterious. Diarrhoea may be present in the first few days of the colt's life, the milk apparently disagreeing with him from the first - those sucking a foster-mother are sometimes upset by their first meal, especially if it happens that the orphan has been put to a mare whose foal was born some time prior to the birth of her adopted one. Here the lacteal secretion is altogether devoid of those aperient properties belonging to the milk of a mare which has recently given birth to a foal, and is consequently less suited to it at this early period of its life.
Diarrhoea is characterized by frequent fluid evacuations; where these are not actually seen the existence of the malady may be gathered from the dirt and stains on the thighs and lower portions of the limbs.
In the stabled horse the premonitory rumblings of the bowels and uneasiness usually escape attention, or they may only occur when the horse is called upon to exert himself. Some "washy" horses, whose faeces are pultaceous or normal in the stable, begin to unload the bowel as soon as the harness or saddle is taken down, and more or less diarrhoea is the result of every journey undertaken. This is unmistakably due to nervous excitability acting upon a susceptible digestive system; and a troublesome condition it is to deal with, since too much work may induce exhaustion and loss of condition, while too little will add to the excitement on each occasion of exercise. In all cases of diarrhoea the ejected material should be examined, when the active cause of the disease may be discovered. If it be woody fibre, it will be found in the liquid matter, or occasional agglomerations of hardened faecal masses of irregular shape will be observed. When a diet of potatoes has induced purging, a very offensive odour accompanies the evacuations, and the mouth is sour and saliva tenacious, while a tendency to abdominal pain may be noted in pawing and crouching as in colic, nausea, and an expression of lassitude and dejection, with a weakened pulse and inappetence, following upon the ordinary symptoms.
In diarrhoea arising from intrinsic causes, general inquiry into the previous health of the animal, or the presence of excessive quantities of biliary matter in the stools, or the discovery of parasites in great numbers, etc, may be of use in directing the prescriber. In the case of the sucking colt with the first fluid evacuations there will probably be no general signs of illness, but with its continuation he loses his appetite for play, and then for milk, stretches himself at full length on the ground and remains prone for a long time, and at intervals looks round at his flank, raising his head from the ground and allowing it to fall back again with an appearance of extreme languor. Abdominal pain of a more acute kind supervening, he will get up and strike at his abdomen with the hind feet, stand with all four feet close together, frequently evacuating offensive yellow faeces, which after a time escape almost involuntarily, staining the thighs, and if he is confined to a building, the atmosphere is soon rendered sour and unwholesome. If the mare and foal are at grass and in deep pasture, the character of the evacuations may escape the notice of the attendant, and not until the foal becomes tucked up in the flank, or dull and listless, does he discover anything amiss. Foals have not so great a power of resistance to diarrhoea as calves, but succumb often in a very few days, with or without inflammation supervening.
When affecting adults, or other than sucking colts, a consideration of the cause will determine the measures to be adopted, which in different cases may be of an almost opposite character, requiring in some the use of aperients or gentle laxatives, while astringents may be called for in others. The chilled animal, having suffered from exposure to inclement weather, will be removed to suitable environment, efforts being made to restore the general circulation with stimulants and friction, as hand-rubbing the limbs, pulling the ears, bandaging, clothing, and the provision of a dry bed; such improved circumstances may alone be found to have reduced the severity of the symptoms without the administration of drugs. The determination of blood to the central organs, which induced diarrhoea, having given place to its proper distribution, as evidenced by increased warmth of the surface and extremities, amelioration of the symptoms will follow in due course. Too early recourse to powerful astringents may lead to an opposite condition, diarrhoea being often a natural method of relieving the body of some deleterious material, and we should be content with astringent foods, as arrow-root and wheat en-Hour gruel, with the addition of a little brandy if the pulse continues weak and the extremities cold. Where diarrhoea is traceable to fermented food of a hard and indigestible nature, it may be advisable to assist its removal with oleaginous fluids, as a dose of castor-oil in warm milk, or linseed-tea, or the distinctly acid nature of the evacuations may point to the use of alkaline bicarbonates as a preparatory measure. Abdominal pain will need to be combated with opium, and cordial carminatives, as cassia, and cinnamon, and ginger, with such diffusible stimulants as nitrous ether, which may be given in gruel. The necessity for giving some fluid food consists in the irritable surface upon which it will have contact, and as soon as there is good reason to hope that the irritability has subsided a return to dry food is advised, as the majority of horses will continue to be loose in the bowels while confined to a diet of slops. As an intermediate diet between gruel and hard food we may use steeped barley and scalded oats, or oatmeal, with milk and eggs well whipped. A mixture of chalk and laudanum suspended in gum and peppermint-water is an old and efficacious remedy, much used for the young. In the treatment of sucking colts it will usually be advisable to give a moderate dose of castor-oil before administering any of the ordinary diarrhoea mixtures. Bismuth, either as a powder or added to the chalk-and-opium mixture, is much favoured in cases of some duration. Lime-water, or bicarbonate of soda in the drinking-water of the mare, will often materially affect the milk and allay intestinal irritation in the foal.