There are several varieties which need not be described.

Good Oats are about one year old, plump, short, hard, rattling when poured into the manger, sweet, clean, free from chaff and dust, and weighing about forty pounds per bushel.

New Oats

New Oats are slightly purgative, indigestible, and unprofitable. They seem to resist the action of the stomach, and to retain their nutriment. They make the horse soft; he sweats soon and much at work. [Oats, and indeed all kinds of grain, are less watery, and therefore more nutritious and sweeter, grown in America than in Great Britain; so that these observations will not hold good entirely, applied to this country.] If they must be used when under three or four months old, they may be improved by kiln-drying. They are not good, however, till they are about a year old. They may be kept till too old, when they become musty and full of insects. The period at which oats begin to degenerate depends so much upon the manner in which they are harvested and preserved, that the age alone affords no rule for rejecting them. They can be kept in good condition for several years.

Fumigated Oats

Fumigated Oats are those which have been exposed to the vapor of ignited sulphur. They are put through this process to improve their color. A good deal of the sulphur adheres to the husk of the oat, which is of a pretty color. A little sulphur can not do the horse any harm, but light small oats absorb a considerable quantity. The sulphur is easily detected by rubbing the oats between the hands a little warmed. When the sulphur is in large quantity, the horses refuse the oats, or they do not feed heartily. I do not perceive that fumigated oats are objectionable in other respects.

Kiln-Dried Oats

Kiln-Dried Oats are those which have been dried by the application of fire. They are generally blamed for producing diabetes; but though this disease is common enough, it does not appear wherever kiln-dried oats are used. In many parts of Russia, oats and all other kinds of grain are kiln-dried in the straw before they are stored. It is not likely that this would be the case if it were so prejudicial to the oats as many people imagine. Most of the kiln-dried oats which are given to horses have been damaged before they were dried, and I suspect that the injury received in harvesting or in storing has more to do with diabetes than kiln-drying has.

Bad Oats

Some oats are light, containing little nutriment in proportion to their bulk; some contain much dust and chaff, small stones, and earth; these can hardly be called good oats, yet there are others which are much worse. Light, husky, and ill-cleaned oats may be sweet and wholesome; if they do little good they do no harm, but some oats are positively injurious to the horse. They may please the eye tolerably well, but they have a bad smell and a bitter disagreeable taste. Horses do not like them. After the first day or two they begin to refuse them. That which they eat produces diabetes, a disease which goes under various names, the most common are staling evil and jaw-piss. I do not know how the oats obtain this diuretic property: many, as I have said, attribute it to kiln-drying, many to the oats having been heated, undergone a little fermentation in the stack or in the granary, and a few ascribe it to the oats being ill-harvested, musty, or half-rotten, before they are got off the field. Oats may be frost-bitten, damaged by insects, or injured in various other ways, but it seems yet uncertain what condition they are in when they produce diabetes: or what makes them so strongly diuretic.

There is no doubt but heated oats will produce diabetes; but whether any other alteration in the oat will have the same effect I do not know. Whatever be the cause, the oats must be changed as soon as it is discovered that they produce.