290            The Nutritive Value of Alkali-treated Cereal Straws

be achieved when almost one-third of the calcium intake was supplied by the
calcium carbonate supplement. When the animals were, however, turned
on to the treated paddy straw in period 4, the calcium balance was entirely
satisfactory. This satisfactory balance was mainly due to the better absorp-
tion of calcium from the treated roughage. This was apparent from the fact
that, out of 23.80 gm.of ingested calcium, barely 6 per cent was absorbed
in period 3, whereas in period 4, out of 22.72 gm. of ingested calcium,
about 16 per cent was absorbed. The marked improvement in phosphorus
absorption during the treated-straw feeding regime was another remarkable
feature of the mineral metabolism of the animals. Out of 13.66 gm. of
ingested phosphorus in period 3, only 10 per cent was absorbed. On the other
hand, in period 4, out of 11.00 gm. of ingested phosphorus, the absorption
of the mineral was over 43 per cent.

Experiment 2

The outstanding nitrogen balance in period 4 suggested the possibility
that the animals can be kept in positive nitrogen balance with a smaller intake
of cake. To test this possibility, immediately after period 4, two animals
(H 45 and H 46) were put back on to a ration consisting of untreated paddy
straw fed ad libitum and the usual quantity of cake. In this case, the allowance
of common salt was withdrawn.

The idea underlying this course of action was to deplete the excess pro-
tein deposited in the body of the animals during period 4. The above feed
was given for about four weeks, towards the end of which time a nitrogen
balance was worked out to determine the exact nitrogen status (period 5)
The results of the nitrogen, calcium and phosphorus balance are shown in
Table XXIX.

                            TABLE XXIX

Nitrogen, calcium and phosphorus balance (period 5)