1. Age

With age, the percentage of nitrogenous matter in plants decreases, and that of woody fibre increases. We cannot, however, assume that the nitrogenous matter in young plants is always as valuable as that in older ones. Dr. Voelcker points out that unripe roots are poorer in sugar than mature roots, and that they contain hurtful organic acids (notably oxalic acid), and imperfectly elaborated nitrogenous matter, which are the cause of their being unwholesome. Therefore, in choosing the period of growth for economically utilising those plants which our horses consume as a whole (eg., grass and clover), we should try to select the happy medium between a maximum of nutriment and a minimum of woody fibre, which as a rule will be obtained in the making of hay from the plants in question, by cutting them during the period of flowering and not later than the first appearance of seed. Further maturity will undoubtedly entail loss in the nutritive constituents of the stalk and leaves, and an excess of woody fibre in them. When plants, like oats, in the ordinary way, are grown for their grain, the nutritive value of their other parts is not considered.

2. Conditions Of Growth (Climate, Soil, Manure, Moisture, Etc.)

The respective percentages of the constituents of plants vary greatly according to their conditions of growth. For instance, hay made from grass grown on rich land, highly manured, and well supplied with moisture, will contain a larger percentage of nitrogenous matter than that made from similar grass produced under less stimulating influences. The nitrogenous matter of the former will, however, be less nutritive as a rule than that of the latter; for the more time is allowed for development, the more complete will be the changes that are necessary to make the constituents of the plant digestible, and to develop those vegetable principles which give flavour to the fodder. It appears that the percentage of fibre is proportionate to the luxuriance of growth. It is a fact of every-day knowledge that fruit which has become ripe in the open air, is more wholesome and better flavoured than similar fruit which has been forced. In the growth of tea we have an admirable instance of the good influence of time in the production of agreeable flavour and in reducing the amount of deleterious constituents. Thus we find in the case of Indian tea, that the slowly growing hill leaves of Kangra Valley, Kooloo and Darjeeling are Tar superior in aroma to the luxuriant low-country leaves of Assam, and that they possess a smaller percentage of compounds which, like tannin, have a hurtful effect on the digestive organs.

The necessity of a full supply of solar heat in the production of fodder for horses, is well shown by the fact that doob grass (creeping dog's-tooth grass; cynodon dactylori), which is the best Indian grass, is grown on dry and poor sandy soil, over which it usually spreads more or less as a creeper. When, on the contrary, it is well watered, it springs up luxuriantly like other grasses, but is not as nutritious as when its growth has been retarded by lack of moisture. The foregoing observations and the knowledge that the digestive organs of the horse are not fitted for the reception of large quantities of coarse fodder, point to the conclusion that grass grown in the shade, or under the influence of stimulating manures, is not a good food for horses. The presence of lime in grass lands, whether naturally or by the addition of bone manure or lime, is an advantage, especially in the rearing of young stock; for the proportion of lime in grass grown on such land is much higher than that in grass produced on soil poor in lime. Soil, climate and manure are such important factors in the production of fodder, that inferior varieties of grass, which are well nourished without being coarse, are superior as a food for horses to the best varieties that are starved or luxuriant.

Harvesting

The mere drying of grass which is necessary to render the resulting hay capable of being stored, in no way affects the digestibility of the hay; but the carrying out of this process may be accompanied by changes which give rise to more or less nutritive loss, and which should consequently be kept in check as much as possible during harvesting.

The action of wet on grass and straw which have been cut, is to more or less dissolve out the soluble nutritive constituents, and to render the nitrogenous matter less digestible. "The amount of depreciation which hay undergoes in a rainy harvest is proved by the fact that 20 per cent. by weight of its dry substance is lost by simply soaking in cold water. Stockhardt examined two kinds of hay, both taken from the same meadow and mown at the same time. One sample had been dried in three days and was housed in its best condition; the other had been left lying in the fields in alternately wet and dry weather for thirteen days before it could be gathered in. Analysis proved that the hay which had been left in the rain had lost 12.5 per cent. by weight of the total dry substance, representing at least a quarter of its original nutritive value, since the loss consisted entirely of the more easily soluble, and therefore especially valuable nutrients (2.1 parts of albuminoids and 10.4 of non-nitrogenous nutrients and mineral salts). After chemical examination in two instances, Marcker calculated the loss of meadow hay through prolonged and heavy rain at 18.4 and 17.6 per cent. of the dry substance. The preparation of clover hay in unfavourable weather is a frequent source of deterioration, for this fodder suffers from rain even more than meadow hay, as from 25 to 40 per cent. of its dry substance can be dissolved in cold water" (Farm Foods).

Growing plants possess a waxy varnish which acts as a protective covering against damp. When the plant dies on being cut, the varnish, if exposed to the action of moisture, soon becomes dissolved, and then washed away. The bruising and rough handling of hay in making and storing is a cause of nutrient loss: for such treatment exposes the softer and more porous inner structure of the plant to the hurtful action of fermentative germs aided by moisture; and inflicts further damage by breaking off a more or less considerable portion of the leaves and other soft parts, which, as we have seen, are far richer in nitrogenous matter than the stalks. Any "heating" (fermentation) which cut fodder may undergo is accompanied by loss of nutritive material. Some of the starch becomes turned into sugar, then into alcohol, if the fermentation is continued, and finally into water and carbonic acid, which escape into the atmosphere in the respective forms of vapour and gas. By this loss, the percentage of fibre in the hay becomes increased. In all cases, any musty smell from either hay or corn will show that the fodder, having become attacked by hurtful bacteria, is more or less unfit for consumption.

As a rule, the more hay is heated in the rick, the browner will it become. Also, before being stacked, it is liable to lose its original green colour from the action of wet on it after it has been cut. Owing to the increase of sugar and possibly to the formation of certain fragrant principles which improve the taste of the hay, we find that horses sometimes prefer brown hay to well-saved green hay, although the former is manifestly of inferior feeding value to the latter; supposing, of course, that the two samples of hay have been made from similar grass. As we have already seen (p. 96 et seq.), the increase in the percentage of fibre in hay, owing to the loss of nutritive constituents, may be no disadvantage to the horse, supposing that this loss is fully-made up by corn. Although, when economy has to be studied, all nutritive loss should be guarded against, I am inclined to think that horses managed on a liberal scale might with advantage have their appetites humoured in this respect, especially when they are hard worked. The change from green to slightly brown hay should of course be made only in the event of the horse preferring the latter to the former. It is probable that with even the best saved hay a certain amount of fermentation, which may be so slight as to cause hardly any appreciable change in the colour of the hay, occurs in all cases when hay has been stacked for some time, and that without it the hay would be wanting in aroma. The conversion of new hay into old hay, appears, therefore, to consist of the further drying of the hay and of the development of flavour; and in ordinary circumstances it may be considered to be complete by the end of January. Hay, even when stored in the most careful manner, suffers continued nutritive loss from slow chemical changes going on in it, and from the breaking off of its leaves; and as its fragrant principles are volatile, it becomes less sapid after they have become fully developed. My experience leads me to believe that "new" hay, even in February, is superior to that which is a year older, other conditions being equal.

Deprivation of water is a well marked advantage gained by corn from keeping. It is evident that the dryer the grain, the more readily will the digestive juices penetrate it, and consequently the more easy of digestion it will be. The fact that properly stored corn has been known to retain its vitality for many years, is a proof that it suffers little or no deterioration from careful keeping. Corn which has been stored, even under the most favourable conditions, appears to undergo a certain amount of fermentation, if we may judge by its change of smell, and by the increase of dust in it. Hurtful fermentation injuriously affects the feeding value of the grain, and may be recognised by the musty smell it imparts to the corn and to the great increase of dust, owing to its action on the surface of the husks. To prevent such fermentation taking place, the corn should be kept dry and well ventilated. A year and a half will generally be sufficient for the thorough drying of corn. There are various forms of fermentation which are respectively produced by special bacteria. As moisture favours the growth and development of these minute forms of vegetable life; the dryer hay and corn are kept, the less chance will they have of being injuriously affected by fermentation.