This section is from the book "The Stable Book: Being A Treatise On The Management Of Horses", by John Stewart. Also available from Amazon: The Stable Book.
When the horse is at home, he is watered either in the stable from a pail, or in the yard from a trough, which, in racing establishments, is provided with a stout lockfast cover as security against poisoning. In general the horse seems to care little how he gets the water; but some will drink only from the trough, except when very thirsty. I know of no objection to the trough, provided it be kept clean, and that the horse do not tremble after drinking from it. The water, however, is often very cold, and the man is often so very lazy that he is unwilling to bring the horse to the door, and he makes two services stand for three. When the horse happens to be in the yard, he may get his water before going in; but at other times it is as well to make it a rule that the water be carried to the stable. Coming from a warm stable to the open air, and drinking cold water, the horse is apt to take a shivering fit. Each stable should be provided with water-pails always full, and standing in the stable.
In watering with a pail, the bucket is either placed on the ground, or raised manger-high to the horse's head. Old short-necked horses drink from the ground with difficulty, yet they always manage it. When the throat is sore, and when the horse is stiff after a day of severe exertion, his water should be held up to him. Some horses rarely drink well, and the less they drink the less they eat. They often require a little coaxing, and always a little patience. It is not enough to offer water and run away with it immediately. Hold the pail manger-high, and keep it before the horse for a little; after washing his mouth and muzzle he may take sufficient to create an appetite.
Post-horses are often watered on the road. They usually receive a little at the end of the stage, and also in the middle of it, if exceeding 9 or 10 miles. On the way home the postboy permits the horse to drink once or twice at watering troughs by the road-side. He has, or should endeavor to have, his horse fully watered and cool by the time they arrive at stables. They are then ready for dressing and feeding without delay.
Horses are often taken to water at a pond or river some distance from the stables. If they need exercise or are passing the water, there is no objection to this practice. But it it is not proper to send working horses out of the stable for the mere purpose of watering them. The weather, the state of the ground, and the laziness of stablemen, render this mode of watering extremely irregular. Boys, too, are often employed in this service, and they are never out of mischief.
With many grooms it is a common custom to give the horse some exercise after drinking. Some give him a gallop, while others are content with a trot or canter for a few hundred yards. Exercise after a copious draught of cold water; is very useful. It does not warm the water in the horse's belly, as the groom says; but it prevents the evil effects which I have adverted to, in connexion with the temperature of water. Motion generates heat, and that which unites with the cold water can be better spared than if the horse were motionless. But the exercise need not be work, It is sufficient if it produce the least perceptible increase of warmth on the skin in 8 or 10 minutes. The man sometimes starts from the water at a gallop, but no good groom is guilty of this folly. Let the horse walk away for a few yards; from a walk he may proceed to a trot, and from that to a canter. In warm weather a walk is sufficient, and the pace need very seldom exceed a slow trot. The object is, not to heat the horse, but to keep him warm, to prevent shivering.
Water is not often given more than three times a day. But in hot weather, when the horse sweats much, he often needs more water than it is safe to give at only three services. He should have it four or five times, and the oftener he gets it, the less he will take at once. Under ordinary circumstances two rules will guide the groom. The first is, never to let the horse get very thirsty; the second, to give him water so often, and in such quantity, that he will not care to take any within an hour of going to fast work. Water should always be given before rather than after grain.
Broken-winded horses are usually much restricted in their water. I know that in stage-coaching they are not the worse of having as much as they please at night, provided it be given at twice or thrice, and not too cold.
 
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