NARAIN DAS KEHAR, R. MUKHERJEE & K. C. SEN 261
It will be observed that the average endogenous
nitrogen values per kg. body weight of bullocks,
1, 5 and 6, during the low-nitrogen period were
0.023, 0.020 and 0.025 and during the nitrogen-
free period 0.018, 0.019 and 0.022 gm. res-
pectively. The average endogenous nitrogen value
of the three animals for the nitrogen-free period
was 0.020 gm. per kg. body weight. The nitrogen
excretion during the nitrogen-free period was al-
most constant from day to day. During the entire
course of this experimental period the animals took
an adequate amount of food and remained in good
condition.
Second experiment
The urinary nitrogen data of Hariana bullocks
are given in Table II. These values represent the
average of the duplicate determinations carried out
independently by two workers. The daily varia-
tion in urinary volume and nitrogen excretion of
these bullocks are shown in Table III. It will be
observed that the average values of endogenous
nitrogen excretion for the last eight days of the
low-nitrogen period and for the eight days of nitro-
gen-free periods of bullocks, 10, 11 and 13, are
0.020, 0.021 and 0.020 and 0.018, 0.022 and 0.018
respectively. The average for all the three ani-
mals during the low-nitrogen period is 0.020 gm.
per kg. body weight and 0.019 gm. during the
nitrogen-free period. These values for the nitro-
gen-free period appear strikingly similar to those
obtained in the case of the hybrid bullocks, not-
withstanding the possible error resulting from vary-
ing quantities of urine excreted by the bullocks,
since it is not possible to empty their bladders by
catheter. It was also observed that, when the
low-nitrogen period is sufficiently extended, the
approximate minimum level of endogenous nitro-
gen excretion is reached. This seems to be borne
out by the results given in Table III.
The above observations suggest that, in the case
of adult bullocks when the urinary nitrogen is
calculated per unit of body weight, the breed
characteristics seem to have little influence on the
endogenous nitrogen catabolism.
Urinary partition products
In order to check any onset of body catabolism
of the animals on the protein-free diet, the non-
protein nitrogen and sulphur fractions in the urine
were estimated, and the results of Hariana and
country bullocks are given in Table IV.
It will be seen that in none of the six animals was
there any increase of urea in the nitrogen-free
period as compared with that in the low-nitrogen
period. This indicates the absence of tissue cata-
bolism during the nitrogen deprivation period and
that the caloric requirements of the animals were
met with from carbohydrates and fats. This fact
is also supported by the presence of only small
traces of creatine, which in large quantities would
indicate tissue catabolism. The values obtained
for sulphur for both the groups of bullocks also
tend to support the same hypothesis.
In comparing the endogenous nitrogen values in
bullocks with those of previous workers on cattle
it will be seen from Table V that our values are the
lowest so far recorded.
The variable results obtained by different work-
ers may be mainly due to the varying amounts of
absorbable nitrogen of unknown biological value
in the rations or their inadequate consumption.
Apparently the ' deposit protein ' is only eliminat-
ed after a considerable period of nitrogen-low feed-
ing. A reasonably long feeding period on low-
nitrogen diet is of extreme importance in eliminat-
ing subsequent errors caused by such deposits, the
extent of which depends on the level and duration
of protein feeding prior to the commencement of
feeding nitrogen-free rations. In the case of pigs,
McColum and Steenbock [1912] have pointed out
that often two or three weeks are required before a
minimal excretion of urinary nitrogen is establish-
ed. In our experiments it took three to four weeks
to attain the endogenous urinary nitrogen level.
These observations may explain the high figures
obtained by Hutchinson and Morris [1936], as they
allowed only six days of preliminary feeding before
collection and six to nine days for the actual experi-
mental period. In addition, it may be remarked
that their diet contained fairly high amounts of
nitrogen.
Attention is drawn to another important aspect
of the question. Terroine and Sorg-Matter [1927]
and Smuts [1935] have shown that endogenous
protein catabolism is related to the basal meta-
bolism. It is now known that the basal metabolism
of Indians is lower than that of Europeans and
Americans, and it is therefore likely that Indian
animals have a lower basal metabolic rate than
those of temperate regions. A lower endogenous
nitrogen level than that found by foreign workers
is, therefore, to be expected in Indian animals.
Further work will, however, throw more light on
this point.
SUMMARY AND CONCLUSIONS
A ' nitrogen-free ' diet for cattle containing as
low as 0.02 per cent nitrogen on dry basis has
been devised, and the nitrogen and sulphur meta-
bolism of bullocks fed on this ration was studied.
The endogenous urinary nitrogen excretion of
bullocks was found to be about 0.020 gm. per kg.
body weight.