The next step in advance, which quite naturally followed, was, to substitute a movable cover of boards, with weights to give the required pressure, for the cover of earth which had been used in the less perfect form of the silo. As an air-tight inclosure was found to be the essential condition in the construction of a silo, lighter walls were made as a matter of economy, with good results, and even frames of timber, lined with boards or planks, were substituted for the more expensive structures, with complete success.
A balloon-frame of scantling, of suitable size, covered on the outside with matched boards, and lined on the inside with two thicknesses of one-inch matched boards, with a layer of tarred paper between them, thus securing a practically air-tight inclosure surrounded by a dead-air space as a protection against frost, is, in the opinion of the writer, the best and cheapest form of construction. If the boards and timbers are saturated with hot coal-tar, which can readily be done with trifling expense, the durability of the silo will be very much increased. From the fact that wood is not so good a conductor of heat as walls of masonry, it will be seen, from what follows, that wooden silos may have an important advantage over any others in preserving the ensilage, which, in connection with the saving of expense in their construction, must have an influence in bringing them into general use.
There are many conflicting statements in regard to the value of ensilage as a cattle-food, and it may be that the failure to realize the exaggerated claims that were made for it when, first introduced has resulted in a reaction which naturally leads to a low estimate of its value. It must, however, be admitted that a large proportion of the farmers who have used it are fully satisfied that it is a desirable and valuable form of cattle-food, and many would not limit its use to the winter months. Others speak with less confidence of the results of their experience, and are inclined to admit, with those who are not convinced of the utility of the process, that the acidity which is developed to a greater or less extent, in most cases, is decidedly objectionable. Experience at the condensed-milk factories is claimed to be unfavorable to ensilage as food for cows, and some of them refuse to receive milk from farms where it is fed.
That there are great differences in the quality of the ensilage made on different farms, or even in that made on the same farm in different seasons, there can be no doubt, and these differences must be attributed to variations in the conditions under which the ensilage is made, which must result in corresponding modifications of the process of fermentation. When the influence of these varying conditions, which include the peculiarities of the crop, as well as the method of filling the silo, is so well understood that ensilage of a uniform and desired quality can be produced with certainty, the most important objections that are now made to it will be obviated, and it will readily take its place on the farm as a staple article of cattle-food.
