STUDIES ON PROTEIN METABOLISM
II. THE EFFECT OF MUSCULAR WORK ON ENDOGENOUS PROTEIN CATABOLISM IN
CATTLE
By NARAIN DAS KEHAR, R. MUKHERJEE, V. V. S. MURTY and K. C. SEN, Animal Nutrition Section,
Imperial Veterinary Research Institute, Izatnagar
(Received for publication on 12 December 1942)
FROM the available literature it appears that no
work on the effect of muscular exercise on the endo-
genous protein catabolism of cattle has been
attempted. Kellner [1926], however, found that
protein catabolism was uninfluenced by work pro-
vided the diet was adequate in energy. On the
other hand, Morrison [1937] suggested that about
double the supply of digestible protein is required
for a horse at hard work as compared with an idle
one. Ramiah et al. [1939] in their investigation on
bullocks found that muscular work was followed by
an increase in the metabolism of protein.
In view of the discordant results obtained by
different observers on the effect of work on protein
catabolism and the great scientific and practical
importance of this problem, it was considered
expedient to study the effect of muscular work on
the endogenous protein metabolism of bullocks,
the chief draft animals in India.
Our plan of work is very similar to that of
Mitchell and Kruger [1928] on rats who state that
the only known method of investigating the extent
of destruction of tissue protein under any experi-
mental conditions is the determination of the
nitrogen content of the urine on a nitrogen-free, but
otherwise adequate, diet so that the exogenous
catabolism is entirely eliminated or is reduced to
an insignificant minimum. Moreover, the pre-work
feeding period on the nitrogen-free diet should be of
sufficient length to remove the ' deposit protein '
from the tissues, since this stored nitrogen would
otherwise render the interpretation of results as
difficult as would dietary nitrogen.
EXPERIMENTAL METHODS
Adult working bullocks of the Hariana breed
weighing 800 to 1,200 lb. were used in this in-
vestigation. Before putting them to this
experiment the animals were fed on low-N
and N-free rations for 45 to 50 days, so that
their urinary nitrogen excretion had already
reached the endogenous level. The details of pre-
paration and feeding of these rations have been
described in Part I of this series. The rations were
designed to supply about 6.0 lb. and 12.8 lb.
starch equivalent during the rest and work periods
respectively per 1,000 lb. body weight according
to the Kellner[1926] standard.
The animals were given the work ration 24 hours
previous to the work period and they continued to
get this ration on the work days. The extra energy
in the work ration was supplied in the form of sago
and sugar.
During the work period, the animals were made
to draw loaded country carts with iron rims for six
hours a day (9 a.m. to 12 noon and 1 p.m. to 4 p.m.)
over a distance of 57,100 ft. The total weight of
the cart and the load thereon was 2,127 lb.
The methods of collection and analysis of urine
adopted in this experiment are the same as those
given in Part I of this series. Twenty-four hours'
samples of urine were analysed for nitrogenous
constituents, except during the work periods of
bullocks 1 and 2, when 12 hours' samples were
analysed separately.
RESULTS AND DISCUSSION
It will be seen from Tables I, II and III that
urinary volume as well as urinary nitrogen and
creatinine fluctuated from day to day. This may
be partly due to the fact that catheter could not
be used and the bladder was not emptied comple-
tely at intervals of 12 or 24 hours. Taking these
daily variations into consideration, it will be observ-
ed from Table I that the daily total nitrogen excre-
tion of bullock 1 during the pre-work period
was approximately of the same quantity as that
during the work and post-work periods. The
nitrogen excretions in the case of other bullocks
are also similar, except for an increase in the nitro-
gen excretion in the post-work period in the case of
bullocks 2, 3 and 5, which may have been due to
fasting catabolism, as the animals during this period
showed acute symptoms of tympanites and refused
their food. The results of 12 hours' samples of
urine (Table I) collected during the two periods,
viz. (i) from 8 a.m. to 8 p.m. covering six hours of
work and (ii) from 8 p.m. to 8 a.m. showed that there
was no increased excretion of urinary nitrogen dur-
ing the course of 72 hours after the animals were
first put to work or 40 hours after the last hour of
work.
The urea, creatine and creatinine figures also
support the above conclusions. The ratio of
creatinine N to total urinary N did not decrease
markedly from the pre-work level (except in the
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