Dec. 15, 1924 
Composition o f Diet, Blood, and Milk 
623 
Palmer (5), in which they found that 
when the protein and energy of the 
ration of milking cows were reduced 
as in Experiment I the composition of 
the milk fat approached that of body 
fab, and further, by the relatively small 
drop in plasma phosphatide as com¬ 
pared with that of the plasma amino- 
N in Experiment I. 
Another interesting indication which 
is given by the results of Experiments 
I, II, and III as shown in Figures 1 and 
3 is that reductions in dietary protein 
tend chiefly to reduce the efficiency for 
milk secretion of the plasma amino- 
acid mixture, while reductions in diet¬ 
ary energy tend to reduce the quantity 
of plasma amino N and perhaps, at the 
the same time, to increase the ineffi- 
S£/>r. 
Fig. 11.—Experiment VII. Change in the compo¬ 
sition of milk. Concentration in period 1 is taken 
as 100 per cent. In period 2 the quality of the 
protein fed was not so good as in period 1; its 
quantity was unchanged 
ciencv for milk secretion of the plasma 
amino-acid mixture. In Experiment I 
the dietary protein and energy were 
reduced together, there was a very 
large reduction in plasma amino N, and 
a large reduction in milk secretion. In 
Experiment III the dietary protein alone 
was reduced, there was a small reduc¬ 
tion in plasma amino N, but a reduc¬ 
tion in milk secretion even a little larger 
than in Experiment I. In Experiment 
II the dietary energy alone was re¬ 
duced, the plasma amino N fell far 
below the normal level, while the reduc¬ 
tion in milk secretion was quite small. 
It seems difficult to explain these rela¬ 
tions, except on the supposition that 
the efficiency for milk secretion of the 
plasma amino-acid mixture was much 
higher in Experiments I and II, where 
the dietary energy was reduced, than in 
Experiment III, where the protein was 
reduced while the energy was kept 
constant. 
SUMMARY 
In experiments on milking cows, 
changes have been made in the energy 
and protein of the rations both sepa¬ 
rately and simultaneously. The pro¬ 
tein has been changed in quantity or 
quality, or both. The effects of these 
changes on the composition and yield of 
milk, on the concentration of amino N 
of the blood and plasma, and, in some 
cases, on the concentration of free tryp¬ 
tophane and other constituents in the 
blood, have been determined. The re¬ 
sults obtained may be summarized as 
follows: 
1. A sharp cut in the energy content 
of the ration of a milking cow produces 
a decided reduction in the plasma amino 
N; with milking cows the energy con¬ 
tent of the ration is an important factor 
in determining the level of plasma 
amino N. 
2. A sharp cut in the quantity of pro¬ 
tein in the ration produced only a slight 
drop in plasma amino N when the 
quality of the protein was unchanged, 
and no drop at all when the quality of 
the dietary protein was reduced along 
with the quantity. 
MO 
/so 
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k 
ki //o 
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so 
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/S 23 23 3 3 /3 A3 
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Fig. 12—Experiment VIII. Change in the com¬ 
position of milk. Concentration in period 1 is taken 
as 100 per cent. In period 2 the quality of the pro¬ 
tein in the ration was decreased without change 
in its quantity: in period 3 the quality was in¬ 
creased above its original level 
3. When a milking cow has been for a 
time on a ration inadequate in protein, 
the quantity of protein may be in¬ 
creased 90 to 100 per cent without an 
increase in plasma amino N. If the 
quality of the dietary protein is im¬ 
proved simultaneously with the in¬ 
crease in its quantity, the plasma amino 
N drops decidedly. 
4. Under appropriate conditions the 
quality of the dietary protein affects 
decidedly the level of plasma amino N 
and the ration containing the more effi¬ 
cient protein mixture is associated with 
the lower level of plasma amino N. 
5. The nutritional condition of an 
animal, as brought about by its dietary 
history, has a very great effect upon the 
level of plasma amino N associated with 
a given ration. 
6. In the case of milking cows, where 
absorption is a fairly constant and con- 
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