190
Methods of Yoking Bullocks
car. As the animal moves forward, the rope is
pulled off the roller, setting the brakes and increasing
the resistance to rotation of the roller. As the car
can only move forward as the rope is allowed to
unwind from the roller, increasing the resistance to
rotation of the roller also increases the resistance to
forward movement of the car. The animal or
animals continue to go forward till the resistance of
the car equals the effort they can or will exert under
the degree of urging applied. In this case the pull
rises continuously to a maximum and must be
measured by some indicating or recording device
interposed in the hitch from the animals to the car.
There is somewhat more literature on recording
apparatus for measuring draft. Most commercial
apparatus available is very expensive and not avail-
able in India and difficult to import in wartime.
Even if available, none of it seemed entirely satis-
factory in one or another respect. The greatest
drawbacks, however, were non-availability and
cost. Collins describes the Iowa traction integrating
dynamometer. This instrument is fairly suitable for
use with some types of apparatus but did not seem
suitable for our purpose, in addition to being un-
available in a reasonable time. The bibliography at
the end of this report gives references to various
articles on recording apparatus.
EXPERIMENTAL PROCEDURE
The decision as to which type of apparatus to
use was difficult. It was finally decided to use two
types of apparatus for the different parts of the ex-
periment. Sharp's simple dynamometer car for the
testing of yokes and a tread mill for the testing of
animals. This choice was partly dictated by the
fact that the dynamometer car could be cheaply
and quickly made available while the tread mill had
to be constructed and would take time. The tread
mill type of apparatus was chosen for the latter
study of effect of body conformation on draft ability
because it facilitated the use of certain auxiliary
apparatus which will be discussed in the report on
that part of the study and because it made standar-
dization of conditions easy.
The lack of any satisfactory recording type of
apparatus made it necessary to choose an indicating
method of measuring the draft. Not even an indicat-
ing dynamometer scale was available, so a large
Salter's spring balance was adapted to the purpose by
adding a second pointer which would record the
maximum pull exerted in any one test. While this
has worked reasonably well, it is hoped that a record-
ing unit will be available in the second part of the
study.
The choice of just what to measure was even more
difficult than how to measure it. It was recognised
that animals do not, when doing ordinary work,
continuously exert the maximum power of which they
are capable. A commonly accepted standard for
loading horses is that the ordinary draft should not
exceed one-tenth of the live weight. The Physiolo-
gical Chemist in the Scientific Reports of the Imperial
Institute of Agricultural Research, Pusa, 1933-34,
in reporting some tests carried out at Pusa, says,
'In these tests the draft has been one-fifth to one-
sixth (of the body weight) and yet the animals did
not show any suffering.'
What we wanted to know was the maximum load
which a given animal could pull in ordinary kinds of
work for ordinary work periods, day after day.
Theoretically, this meant a load which would result
in a state of fatigue at the end of the work period,
beyond which it would be undesirable or dangerous to
go. We found no method of testing the state of
fatigue and no standard maximum state of fatigue
which an animal could bear. It is known of course
that if an animal or a man works beyond his normal
capacity, he loses condition, becomes leaner and
eventually may develop other symptoms, or even
collapse entirely, if the overloading is carried to
great extremes. Such effects ordinarily only show
up after long periods, too long at least for us to use
them for purposes of this research. Various methods,
such as blood analyses, were suggested as 'possibly'
offering a means of determining fatigue. These did
not seem suitable because there was no standardized
procedure or any correlation known between the
results of the analysis and the degree of fatigue.
To have tried to work out such standards would
have taken more time than was available. Collins
and Caine say 'It is practically impossible at present
to determine the state of fatigue of an animal. Ex-
perienced horsemen may observe the general condition
of an individual but they cannot determine the
actual physical condition and know exactly if the
horse is approaching a state of fatigue. In two
years of experimental work where horses were pulling
loads equivalent to a horse power or more for eight
hours per day, day after day, they showed no out-
ward signs of a fatigued condition;....'. Si nce
we found no end point which could be definitely
determined, in tests using loads comparable to
ordinary working loads, it was necessary to choose
something for our tests which could be definitely
determined. We realized that we do not yet know
exactly the relation between the maximum load an
animal or pair of animals can pull and the load they
should be expected to pull day after day. Horse
pulling contests and other testing in America has
shown however that, in general, pulling contests
are generally won—that is maximum pulls are
made—by animals which are known to be good
workers. We therefore feel justified in assuming
that in bullocks also, there is a relation between
maximum load pulled and draft ability as generally
applied under ordinary working conditions.