Dec. 15, 1924 
Composition o f Diet , Blood, and Milk 
611 
Table V.— Experiment III, cow 422 . Change in the quantity of protein in the 
ration; no change in its quality 
Period 
No. 
Date 
Milk (daily) 
Amino N® 
Yield 
Fat 
Nitrogen 
Blood 
(mg. per 
100 c. c.) 
Plasma 
(mg. per 
100 c. c.) 
1921 
Kg. 
P. ct. 
Gm. 
P. ct. 
Gm. 
1_ 
Sept. 16-21_ 
8. 65 
5. 01 
433 
0.643 
55.6 
b 4. 22 
b 2.45 
2_ 
Sept. 22 «_ 
2_ 
Sept. 25___ 
7.12 
4.80 
342 
.613 
43. 7 
2.. 
Sept. 26. .. 
6.99 
4.98 
348 
.613 
42.2 
2. 
Sept. 27_ 
6. 76 
4.81 
325 
.625 
42.2 
2_ 
Sept. 28_ 
6.12 
4. 74 
290 
.643 
39.3 
3. 76 
2.17 
2_ 
Sept. 29. 
6.31 
4.65 
293 
.620 
39.1 
2__ 
Sept. 30_ _ 
6.49 
4. 55 
295 
.623 
40.4 
2.. 
Oct. 1.. 
5. 85 
5.38 
315 
.628 
36.7 
2_ 
Oct. 2.. 
5. 72 
4. 78 
273 
.600 
34.3 
2_ 
Oct. 3_ 
5. 67 
5.03 
285 
.660 
37.4 
2 ... 
Oct. 4 e .. 
3.76 
2.36 
2 . 
Oct. 6__ 
5. 53 
5. 77 
320 
.636 
35.2 
2 _ 
Oct. 7__ 
5.31 
5. 57 
296 
.640 
34.0 
2 .. 
Oct. 8_ 
5.44 
5. 30 
288 
.644 
35.0 
2 _ 
Oct. 10 c_ 
3.. 
Oct. 11 *_ 
5. 67 
4.96 
281 
.644 
36.5 
■3_ 
Oct. 12.. 
6. 40 
5.03 
322 
.606 
38.8 
3_ 
Oct. 13_ 
6. 80 
6.14 
418 
.643 
43.7 
3_ 
Oct. 14_ 
6. 89 
4.83 
333 
.679 
46.8 
4.73 
3.. 
Oct. 15..... 
6.58 
5. 83 
383 
.705 
46.4 
3_ 
Oct. 16_ 
6. 99 
5.94 
415 
.712 
49.8 
3_ 
Oct. 17.. 
6. 89 
5.94 
410 
.722 
49.8 
4.36 
2.33 
3 .. 
Oct. 18. 
6. 99 
5. 90 
412 
.710 
49.6 
3_ 
Oct. 19_ 
7.21 
5.77 
416 
.676 
48.8 
3_ 
Oct. 20.. 
7. 22 
5. 92 
427 
.682 
49.2 
3.... 
Oct. 21__.. 
7.26 
5.74 
417 
.732 
53.2 
3___ 
Oct. 22... 
7.08 
6.45 
456 
3.. 
Oct. 25. 
7.54 
6.35 
478 
.722 
54.4 
3_ 
Oct. 26_ 
7.12 
6.25 
445 
.750 
53.4 
4.63 
2.36 
3_ 
Oct. 27. 
6. 85 
6. 33 
433 
.748 
51.2 
3.. 
Oct. 28. 
7.44 
3. 94 
2.20 
3.... 
Oct. 29. 
7.12 
6.24 
444 
.729 
51.9 
“Average difference in duplicate amino-N determinations in blood 4.9 per cent, and in plasma 3.1 per 
cent. 
b Sample taken Sept. 19. 
c Feed refused or withheld: Sept. 22, grain 2.01 kg.; Oct. 4, silage 1.97 kg. and grain 1.38 kg.; Oct. 10, grain 
1.1 kg.; Oct. 11, grain 3.43 kg. 
In Experiment III, in which the 
quantity of dietary protein in the ration 
was reduced without change in its 
quality 4 or in the energy content of the 
ration, there was initially a slight drop 
in plasma amino N. In period 1 it 
was 2.45 mg. Six days after the change 
of ration it was 2.17 mg., or 11.4 
per cent lower. This is hardly con¬ 
siderable. 
A comparison of the curves in Ex¬ 
periments I and III shows plainly that 
the cut in the energy along with the 
protein in Experiment I increased 
decidedly the abruptness and magni¬ 
tude of the drop in plasma amino N. 
4 By quality here we mean the amino acid com¬ 
position of the mixture of dietary proteins. Wher¬ 
ever used with reference to proteins in this paper, 
it is used in this sense. By a protein of good quality 
we mean one that because of its amino acid compo¬ 
sition can be used efficiently in the synthesis of 
milk and tissue proteins. 
From this and from Experiment II it 
is evident that a sharp cut {23 per cent) 
in the energy content of the ration of a 
milking cow brings about a decided reduc¬ 
tion in plasma amino N. The energy 
content of the ration is an important fac¬ 
tor in determining the level of plasma 
amino N. 
The curve in Experiment V shows 
that no change in plasma amino N 
occurred when the quality as well as the 
quantity of the dietary protein was 
reduced. In period 1 the plasma 
amino N was 2.43 and 2.55 mg., and in 
period 2 it was 2.47 and 2.53 mg. This 
result, compared with that in Experi¬ 
ment III, suggests that the quality of 
the dietary protein may affect the level 
of plasma amino N. (See later.) Ex¬ 
periments III and V indicate that a 
sharp cut of 50 per cent in the dietary 
protein with a milking cow often does not 
