G.
WILLIAMSON
65
sodium hydroxide solution, a volume of fresh water
is run on to it until the basin is brimful. The
heavy caustic solution lies practically undiluted at
the bottom of the basin and is now by a simple but
ingenious system of piping syphoned off to the
neighbouring basin for use on the next consign-
ment of straw, while the head of water which has
permitted the syphoning of the soda is diverted to
an outside channel as is the water with which the
straw continues to bo washed until it has lost all
feeling of soapiness. That process may take from
one to three hours, depending upon the rate at
which the water is being passed through. The
straw is then fit for immediate feeding, but is
usually allowed to drain for an hour or two in order
to get rid of surplus fluid. The caustic solution
which has been syphoned into the second basin
is made up to the original strength and volume and
the process is repeated.
The other type of plant is yet more simple, but
involves a somewhat greater amount of work. It
consists of two tanks separated by a drainage
platform. After the chopped straw has been
soaked in one tank it is ladled on to the platform
from where the surplus lye runs back to the tank
from where it was lifted. The straw is then shovel-
led into the second tank, where it is washed by
successive steepings in water or by a continuous
stream of water. Again, it is generally found to
be advisable to drain the surplus liquid from the
straw before feeding. In either plant there is some
difficulty experienced in the initial soaking, but
that is overcome by means of sectional wooden
frames over which half-inch wire netting is spread.
These are placed on the straw, and with the help
of heavy concrete weights they press the straw
down into the solution.
The action of the caustic solution on the straw
is most intensive for a comparatively short period
during the first hour or two. Beckmann himself
considered that three hours was the optimum time
for soaking, but the process of digestion actually
continues after the first three hours, although pro-
gress then is very slow. In practice it often proves
convenient to soak the straw overnight and wash
it first thing in the morning. The process will
certainly have gone as far as desirable by twenty
hours with the temperature at 45°F., but if the
weather is cold and the temperature at, say, freez-
ing-point, the straw must be exposed to the action
of the salt for very much longer if the same degree
of digestion is to be attained. As indicated,
however, something considerably short of twenty
hours is sufficient for practical purposes.
The amount of water required for washing is
about four gallons for each pound of straw. The
time required to handle 200 lb. of straw by one
man is three-quarters of an hour. The all-in cost
of the treatment at present prices in Britain is in
the region of £3 per ton.
The straw is generally fed in the wet state and
when stock have once become used to it they eat
it readily. Some animals take to it at once, but
other individuals come to it more slowly. We
have, however, seen cattle, coming straight from
good grazing, accept the pulped straw almost
immediately, and we have seen horses accustomed
to good rye-grass hay readily accept the treated
straw in its place. There is, however, no reason
on the score of palatability why the straw should
not be dried and stored. During the drying pro-
cess, however, when the material is damp rather
than wet, it is liable to ferment and become
musty, but once that stage, so favourable to the
growth of moulds, has passed the treated straw will
keep as well as it did before treatment.
As already indicated, the treatment more or less
doubles the starch equivalent value of the straw
for ruminants—that is, it brings the energy-produc-
ing value of oat straw up to level of that of the
cereals, and of wheat straw to that of really good
hay. It is probable that for horses the value of
the straw is raised relatively more than it is for
ruminants ; in fact, a digestibility experiment with
these animals showed that a poor barley straw
with a starch equivalent as low as 5.5 per cent
was raised to an equivalent of 20.2 per cent which
brings it to the comparative value of poor hay.
As a food, however, its almost complete lack of
protein must be remembered and that deficiency
must be made good by a supplement. In Germany
in [Fingerling 1917] horses fed solely on such a
mixture maintained good condition while being
subjected to hard work, while in 1919 hydrolized
wood meal with a protein supplement was
substituted for hay and even for oats with
satisfactory results. [Ellenberger 1919] We
have found that resting horses maintained
their condition over a period of four months during
which caustic-treated straw took the place of hay.
So far as we know, progress in the methods of
treating straw on a farm scale so as to overcome its
natural indigestibility rests at the stage to which
Beckmann brought it. Some refinements have
been added, but the principles remain substantially
unaltered. In practice, there are many difficulties
connected with it, but most of them have been
exaggerated in prospect and have disappeared on
acquaintance. One unaccustomed to the work
would immediately question the advisability of
allowing the free use of such potentially dangerous
material as caustic soda, both to humans and to
stock, but a few simple precautions overcome the
difficulty and no real objection to it is ever offered
by those using the material. More serious objec-
tions are those made on economic grounds—the
cost of soda, the necessity of washing and the