K. P. BASU AND K. P.
MUKHERJEE
237
experimental diets for three weeks. Table II gives
the composition of the experimental diets and of
the salt mixture. The diets, were so planned that
they contained almost the same percentage of cal-
cium, phosphorus and proteins. The calcium : phos-
phorus ratio was always maintained at the same
value. The phosphorus of the diets was derived
entirely from cow, goat or buffalo milk under
investigation. Reliable results regarding the avail-
ability of phosphorus from a particular source are
obtained by employing a diet the phosphorus of
which is derived entirely from the foodstuff
under investigation and in this respect the diets
employed in this investigation are to be preferred
to those employed by William, MacLeod and
Morrell [1940]. The diets were preserved in
suoppered glass jars and stored in a refrigerator.
Vitamins A, D and also B complex were given
twice a week to the experimental rats.
The animals were so chosen that the average
initial weights of the group of rats to be compared
were approximately the same. In all cases litter
mates of the same sex were compared. Food and
distilled water were supplied to the rats ad libitum
and records were kept for the food supplied, any
food spilled was carefully separated from the
faeces and collected. In each case the total
amount of food supplied was taken into consi-
deration while calculating the total food intake.
Records were kept of the growth of the animals
during the experiments and are shown in Table
III. It was observed that all the animals con-
sumed less amount of food and consequently
showed less growth than in the case of usual
optimal intake of food. But all the animals
consumed nearly the same amount of food and
the average growth rates of rats on the milk diets
was the same.
At seven weeks of age the rats were weighed,
killed with chloroform, brushed to remove any
adhering food particles from the fur. The gastro-
intestinal tract was dissected out and the contents
removed. The weight of the contents substracted
from the final live weight gave the net weight
which was used as a basis in calculating the per-
centage of body phosphorus of seven weeks old
rats. The alimentary tract was discarded though
the phosphorus content of the intestinal tract was
not negligible but was low in comparison with that
of the food remnants. The animals were ashed
in ica basin first over a low flame and finally
in an electric muffle furnace adjusted so that it
maintained a temperature between 550º—575ºC.
After ashing for 12 hours the ashes were taken
out and stirred thoroughly with a rod and finally
it was washed with distilled water and the wet
ash was allowed to dry on the water-bath and was
again put into muffle furnace for another 12 hours ;
unless this is done, ashing would not be complete
at such controlled temperatures. The ashes were
dissolved in 6 c.c. concentrated HCl with 25 c.c.
of distilled water with boiling, filtered and diluted
to 250 c.c. Aliquots of the solution were analyzed
for phosphorus by the method already stated.
The results are summarized in Table IV. The
bodies of female rats on the buffalo-milk, goat-
milk and cow-milk diet contained respectively
0.506±.005, 0.517±.004 and 0.512±.005 per
cent of phosphorus. It will be noticed that rats
on the different milk diets had approximately
the same percentage of body phosphorus. The
difference is insignificant. This is to be expected
since the rats on the different milk diets grew at
the same rate as is evident from Table III.
To obtain the storage of phosphorus it was
necessary to know the initial phosphorus content
of the body of the animals just before the beginning
of the experiment. This was obtained by determin-
ing the percentage of body phosphorus with
litter mates weighing 37 gm. The method adopted
to determine the total body phosphorus of these
animals was exactly the same as described previ-
ously for the experimental animals. The results
are tabulated in Table V. It will be observed
that the prercentage of body phosphorus of 37
gm. weight (four weeks old) rats of different
litters on the same laboratory stock diet before
the experimental period was practically the same.
For an exact basis of comparison a phosphorus
utilization factor was calculated for each of the
diets. This was obtained by dividing the phospho-
rus retention by the intake and the utilization
factor has been expressed in percentage by multi-
plying this value by 100. The average phosphorus
utilization factors expressed in percentage for
each of the diets are given in Table VI. The
values for the female rats were 81.7 for the buffalo-
milk diet, 83.7 for the goat-milk diet and 82.1
for the cow-milk diet. The difference in the values
found is very small. These differences are not
significant and it appears that the phosphorus of
the milks of the above-mentioned animals is
utilized to the same extent.
TABLE II
Composition of the diets in percentage
Egg albumin .
Butter fat . .
Starch . .
Salt mixture .
Whole dried milk .
Phosphorus . .
Calcium . .
Protein (N × 6.25)
Cow milk diet.
12
8
49
5
26
100
. 18 per cent
. 25 per cent
20.32 per cent
Goat milk diet.
12
8
45
5
30
100
. 18 per cent
. 25 per cent
20.22 per cent
Buffalo milk
diet.
12
8
45
5
30
100
.18 per cent
.27 per cent
20.14 per cent