A. J. MACDONALD AND S.
BOSE
113
During periods 1 and 2, the birds in Group 5
consumed slightly more food than those in the
other three groups. The birds in Group 5, how¬
ever, were heavier throughout and made better
utilization of their food as judged by the food
consumed per pound of live weight gain. During
the final period of four weeks the birds in all four
groups consumed somewhat similar amounts of
food. Group 5 made slightly better utilization
of the food consumed than Groups 6, 7 and
8. The food utilization figures were again very
similar for Groups 6, 7 and 8.
Protein consumption. Table VIII gives details
of the protein percentages in the foods consumed
during each of the four-weekly periods.
TABLE VIII
Percentage protein consumption
Period
1. 1-5 weeks . .
2. 5-9 weeks . .
3. 9-13weeks . .
Group 5
14.9
13.8
13.5
Group 6
14.6
14.5
13.4
Group 7
14.6
14.2
13.4
Group 8
14.6
14.3
13.7
The percentages of protein in the food consumed
by the four groups were very similar for each of
the respective periods. During period 1, Group 5
consumed a slightly higher percentage of protein
than Groups 6, 7 and 8 but in period 2 the
figures were reversed. During the final period of
four weeks on the standard diet, the percentages
of protein consumed were very similar for all four
groups.
Mortality. All the groups had a very good
health record throughout but, as in Experiment 1,
the birds on the milk ration behaved better and
had a more thriving appearance than those in the
other three groups. No apparent differences
in handling or in appearance were observed bet-
ween the birds in Groups 6, 7 and 8. The mor-
tality percentages from 1—13 weeks in Groups
5—8 were 1.2, 3.6, 8.4 and 8.4 respectively.
DISCUSSION OF RESULTS
Cereals in conjunction with adequate amounts
of green food and calcium supplemented with
separated milk only to drink during the early
stages of growth gave satisfactory growth results,
low mortality and economic food utilization in
both experiments. As reported earlier by Mac-
donald [1941], rations supplemented with separated
milk proved satisfactory at all stages, even though
the percentage protein consumed was very much
lower than that generally recommended (20 per
cent) by other workers, The satisfactory results
outlined with low protein levels with separated
milk in the ration may not be applicable in the
case of other cereal diets with proteins of a lower
biological value. In America where maize meal nor-
mally is fed in the ration at a level of 50 per cent or
over, it is probable that higher levels of protein
would be required to give similar results. It is not
suggested that higher rates of growth might not
have been obtained with higher levels of protein but
from the commercial aspect the results with even
less than 15 per cent protein, in the diet can be
considered satisfactory and it is very doubtful
whether feeding for a higher growth rate would
be justified on account of the high costs of
protein supplements.
As in former experiments by Macdonald [1941],
the soya bean meal and salt supplement proved
inferior to a supplement of separated milk. In
both of the experiments under report, extracted
soya bean meal or heated extracted soya bean
meal gave no better results than soya bean meal.
The results are contradictory to the findings of
various American workers that extracted soya bean
meal gave better results than soya bean meal and
that extracted soya bean meal heated at a high
temperature gave even better results than ex-
tracted soya bean meal. No satisfactory expla-
nation for the apparent contradictory results can
at present be formulated without further extensive
experimental work. The results of the two ex-
periments carried out do not, however, disprove
that heating extracted soya bean meal does not
improve its biological value but merely demons-
trate that the addition of the heated product did
not improve the biological value of the rations
used. Two possible hypotheses may be put for-
ward as an explanation for the difference in the
results obtained; (1) that the basal ration may
have been richer than those used in America in the
essential factors required and (2) that the soya bean
meal used may have contained more readily
available combinations of amino-acids.
The higher fat content of soya bean meal is
regarded as harmful, as chickens, especially during
the early stages of growth, make poor utilization
of rations rich in fat. In Experiments 1 and 2
the fat contents of the soya bean meal mash were
6.9 and 6.8 per cent respectively. The corres-
ponding figures for the extracted soya bean mashes
were 5.2 and 5.2. In actual practice with com-
bined mash and grain feeding the fat content in
the soya bean ration was only approximately 1
per cent greater than that in the extracted soya
bean ration. In the experiments under report, the
slightly higher fat content in the soya bean meal
ration did not appear to have any retarding in-
fluence on the rate of growth or the utilization of
the food consumed.