Dec. 15, 1924 
Composition of Diet , Blood, and Milk 
609 
DISCUSSION 
It will be convenient to consider the 
data in these experiments in the fol¬ 
lowing order: 
1. Changes in the composition of the 
blood produced by the changes in the 
rations. 
2 . Changes in the yield and compo¬ 
sition of the milk produced by the 
changes in the rations. 
3. Physiological relations between 
the composition of the blood and the 
secretion of milk, 
CHANGES IN THE COMPOSITION 
OF THE BLOOD 
An inspection of Tables III to X 
will readily give some idea of the con¬ 
centrations of plasma amino N that 
may occur under normal conditions. 
There are 11 determinations in these 
experiments made with cows that had 
been fed ordinary feeding materials, 
containing approximately the quantity 
of protein, and from 85 to 102 per cent 
of the energy, which would be required 
according to the Savage standard, the 
feeding being continued for a sufficient 
length of time to give an idea of the 
normal plasma amino N under these 
conditions. The figures varied from 
2.20 to 2.64 mg. per 100 c. c. of blood 
plasma. 
Figure 1 shows the changes in plasma 
amino N that occurred as a result of 
Fig. 1— Effect on plasma amino N of reducing the 
protein (50 per cent) or energy content (33 per 
cent), or both, in the ration of a milking cow after 
a period on an adequate ration. Except in Ex¬ 
periment IV, the initial determinations give the 
level of plasma amino N in the first periods just 
before the rations were changed 
Experiment I—Energy and protein content 
of ration reduced 
Experiment II.—Energy content of ration 
reduced 
Experiment III.—Amount of protein reduced; 
no change in quality 
Experiment IV.—Amount of protein reduced; 
no change in quality. No amino N deter¬ 
minations were made before the change of 
ration. This curve, like the others, shows 
a tendency for concentration of amino N to 
return to normal even while ration is still 
inadequate 
Experiment V—Quantity and quality of 
protein reduced 
Table III.— Experiment 7, cow 17. Results of changing the energy content and the 
quantity of protein in the ration 
Period No. 
Date 
Milk (daily) 
Blood 
Yield 
Nitrogen 
Fat 
Amino N * 
Plasma 
lipoid 
phos¬ 
phorus 
(mg. 
per 100 
c. c.) 
Blood 
(mg. 
per 100 
c. c.) 
Plasma 
(mg. 
per 100 
c. c.) 
1 . 
1920 
May 1-10.. 
Kg. 
12.85 
12. 93 
12. 25 
10.71 
9. 89 
9. 89 
9.89 
10.30 
8.84 
9.21 
8 . 47 
7.94 
8.16 
7. 76 
7.80 
8.26 
10.84 
9.43 
9. 30 
9. 25 
9.03 
P. ct. 
Gm. 
P. ct. 
Gm. 
1 _ 
May 11_ 
0. 5045 
.4922 
.5211 
.4964 
.4911 
65.23 
60.28 
55. 78 
49.08 
48.56 
3.43 
443.9 
4.10 
2.30 
7.8 
2 . 
May 12_ 
2 __. 
May 13.. 
4.04 
3.88 
3.93 
432.8 
384.1 
388.7 
3.74 
1.77 
2 . 
May 14____ 
2 _ 
May 15. 
3.23 
1.25 
7.0 
2 . 
May 16-18_ 
2 .. 
May 19 . 
.4676 
48.15 
3.48 
358.7 
2 ... 
May 20-27__.. 
2 .. 
May 28... 
.4738 
43.63 
3.32 
304.1 
2 _ _ . 
May 29-June 1_ 
2 _. 
June 2_ 
.4600 
36. 30 
3. 62 
284.3 
2 _ 
June 3.. 
3.03 
1.63 
2 __. 
June 4-6_ 
2 . 
June 7__. 
.4848 
37.83 
3.61 
. 281.4 
3.05 
1.66 
6.3 
3__. 
June 8_ 
3.. 
June 9 _ 
.5292 
57.13 
3. 81 
423.3 
3_. 
June 10_ 
2. 75 
1.57 
3_ ... 
June 11 __ 
3.94 
366.4 
3_.. 
June 12-23.... 
3_ 
June 24__ 
3.63 
2.64 
° Average difference in duplicate amino-N determinations, in blood 9.2 per cent, and in plasma 9.8 per 
cent. 
