By FREDK. JAS. LLOYD, F.C.S., Lecturer on Agriculture, King's College.

The recently published number of the Royal Agricultural Society's Journal contains some information upon the subject of silage which appears to me of considerable interest to those chemists who are at present investigating the changes which take place in the conversion of grass into silage. The data1 are, so far as I know, unique, and though the analytical work is not my own, yet it is that of an agricultural chemist, Mr. A. Smetham, of Liverpool, whose work I know from personal experience to be thoroughly careful and reliable. I have therefore no hesitation in basing my remarks upon it.

We have here for the first time an accurate account of the quantity of grass put into a silo, of the quantity of silage taken out, and of the exact composition both of the grass and resulting silage. I desire merely to place myself in the position of, so to speak, a "chemical accountant."

The ensilage has been analyzed at three depths, or rather in three layers, the first being 1 foot, the second 1 ft. to 1 ft. 6 in., and the third 1 ft. 6 in. to 2 ft. from the bottom of the silo. By doubling the figures of the bottom layer analysis, adding these to the second and third layer analysis, and dividing by 4, we obtain a fair representation of the average composition of the silage taken throughout the silo, for by so doing we obtain the average of the analyses of each 6-inch layer of silage. The results of the analyses are as follows, calculated on the dry matter. The moisture was practically the same, being 70.48 per cent, in the grass and 72.97 in the silage.

Composition of Grass and Silage (dried at 100°C.).

The striking difference in the mineral matter of the grass and silage I will merely draw attention to; it is not due to the salt added to the silage. I may say, however, that other analysts and I myself have found similar striking differences. For instance, Prof. Kinch 2 found in grass 8.50 per cent. mineral matter, in silage 10.10 per cent., which, as be points out, is equivalent, to a "loss of about 18 per cent. of combustible constituents" - a loss which we have no proof of having taken place. In Mr. Smetham's sample the loss would have to be 50 per cent., which did not occur, and in fact is not possible. What is the explanation?

I am, however, considering now the organic constituents. Calculating the percentages of these in the grass and silage, we obtain the following figures:

Percentage Composition of Organic Compounds.

The difference in the total nitrogen in the grass and silage is equal to 0.68 per cent. of albuminoids. Practically it is a matter of impossibility that the nitrogen could have increased in the silo, and it will be a very safe premise upon which to base any further calculations that the total amount of nitrogen in the silage was identical with that in the grass. There may have been a loss, but that is not yet proved. Arguing then upon the first hypothesis, it is evident that 100 parts of the organic matters of silage represent more than 100 parts of the organic matter of grass, and by the equation we obtain 10.75:11.43 :: 100:106 approximately. If now we calculate the composition of 106 parts organic matter of grass, it will represent exactly the organic matter which has gone to form 100 parts of that present in silage.

The following table gives these results, and also the loss or gain in the various constitutents arising from the conversion into silage:

Organic Matter.

These calculations show, provided my reasoning be correct, that the chief changes which take place are in the albuminous compounds, which has already been pointed out by Professors Voelcker, Kinch, and others; and in the starch, gum, mucilage, sugar, and those numerous bodies termed extractives, which was to be expected. But they show most conclusively that the "decrease in the amount of indigestible fiber and increase in digestible" so much spoken of is, so far as our present very imperfect methods of analyzing these compounds permit us to judge, a myth; and I have not yet found any sufficient evidence to support this statement. A loss, then, of 6 parts of organic matter out of every 106 parts put into the silo has in this instance taken place, due chiefly to the decomposition of starch, sugar, and mucilage, etc. And as the grass contained 70 parts of water when put into the silo, the total loss would only be 1.7 per cent. of the total weight. This theoretical deduction was found by practical experience correct, for Mr. Smith, agent to Lord Egerton, upon whose estate this silage was made, in his report to Mr. Jenkins says the "actual weight out of the silo corresponds exactly with the weight we put into the same."

In my judgment these figures are of interest to the agricultural chemist for many reasons. First, they will clear the ground for future workers and eliminate from their researches what would have greatly complicated them - changes in the cellulose bodies.

Secondly, they are of interest because our present methods of distinguishing between and estimating digestible and indigestible fiber is most rough, and probably inaccurate, and may not in the least represent the power of an animal - say a cow - to digest these various substances; and most of us know that when a new method of analysis becomes a necessity, a new method is generally discovered. Lastly, they are of interest to the agriculturist, for they point out, I believe for the first time, the exact amount of loss which grass - or at least one sample - has undergone in conversion into silage, and also that much of the nitrogenous matter is changed, and so far as we know at present, lost its nutritive value. This, however, is only comparing silage with grass. What is wanted is to compare silage with hay - both made out of the same grass. Then, and then only, will it be possible to sum up the relative advantages or disadvantages of the two methods of preserving grass as food for cattle. - Chem. News.

[1]

Royal Agricultural Society's Journal, vol. xx., part i., pp. 175 and 380.

[2]

Journ. Chem. Society, March, 1884, p. 124.