=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.