Principles and practice of agricultural analysis. Volume 3 (of 3), Agricultural products

by Harvey Washington Wiley

532. General Principles.—The analyst, in examining the fibrous foods of cattle, is expected to determine moisture, ash, fiber and other carbohydrates, ether extract and albuminoid and amid nitrogen. If a more exhaustive study be required, the sugar and starch are separated from the other non-nitrogenous matters, the carbohydrate bodies yielding furfuraldehyd separately determined and the ash subjected to a quantitive analysis. The processes are conducted in harmony with the principles and methods of procedure fully set forth in the preceding pages.

Green fodders and grasses are easily dried and sampled by comminution in the shredder described on [page 9], and roots by that shown on [page 10]. The moisture is determined by drying a small sample of the shredded mass, while the rest of it is dried, first at about 60° and finally at 100°, or a little above, ground to a fine powder and subjected to analysis by methods already described. The food values as obtained by analysis should be compared, when possible, with those secured by natural and artificial digestion.

Ensilage is shredded and analyzed in precisely the same way, but in drying, the content of volatile acids formed during fermentation must be considered. In other words, the loss on drying ensilage at 100°, or slightly above, is due not only to the escape of water but also to the volatilization of the acetic acid, which is one of the final products of fermentation which the mass undergoes in the silo.

533. Organic Acids in Ensilage.—In the examination of ensilage, the organic acids which are present may be determined by the processes described in following paragraphs. The acetic acid, formed chiefly by fermentation, is conveniently determined by the method given for tobacco further on. Lactic acid is detected and estimated by expressing the juice from a sample of ensilage, removing the acetic acid by distillation, repeated once or twice, and treating the filtered residue with zinc carbonate in excess, filtering and determining the zinc lactate in the filtrate. The zinc is determined by the method described for evaporated apples and the lactic acid calculated from the weight of zinc found. Crystallized zinc lactate contains 18.18 per cent of water and 27.27 per cent of zinc oxid.[540]

534. Changes due to Fermentation in the Silo.—Silage differs from green fodder in having less starch and sugar, more acetic and lactic acids and alcohol and a higher proportion of amid to albuminoid nitrogen.[541] There is also a considerable loss of nitrogenous substances in ensilage, due probably to their conversion into ammonium acetate, which is lost on drying.

535. Alcohol in Ensilage.—The fermentation which takes place in the silo is not wholly of an alcoholic nature, as the development of lactic acid, noted above, clearly indicates. The alcohol which is formed may escape and but small quantities can be detected in the ripened product. So small is this quantity of alcohol that it appears to be useless to try to secure a quantitive estimation of it. Qualitively, it may be detected by collecting it in a distillate, which is neutralized or made slightly alkaline with soda or potash lye and redistilled. The greater part of the alcohol will be found in the first few cubic centimeters, which are made alkaline with potash lye and as much iodin added as can be without giving a red tint to the solution. Any alcohol which is present will soon separate as iodoform.

536. Comparative Values of Fodder and Ensilage.—In judging of the comparative values of green and dry fodders for feeding purposes, it is necessary to secure representative samples in the green, quickly dried and ensilaged condition. It is quite certain that the greater part of the sugar contained in green fodders is lost both by natural curing and by placing in a silo. When well cured by the usual processes there is but little loss of nitrogenous matters, but in the silo this loss is of considerable magnitude, amounting in some instances to as much as thirty per cent.

The ideal way of preparing green fodders in order to preserve the maximum food value efficiently, is to shred them and dry rapidly by artificial heat, or in the sunlight, until they are in a condition which insures freedom from fermentation. In this condition, when placed in bales, under heavy pressure, the food constituents are preserved in the highest available form. The immense sugar content of the stalks of maize and sorghum could be preserved in this way almost indefinitely.

FLESH PRODUCTS.

537. Names Of Meats.—The parts of the animal from which the meats are taken have received distinctive names, which serve to designate the parts of the carcass offered for sale. These names are not invariable and naturally are quite different in many markets. In this country there is some degree of uniformity among butchers in naming the meats from different parts. The names in scientific use for the parts of mutton, beef and pork are found in the accompanying illustrations.[542]