470 
Journal of Agricultural Research 
Vol. XXXI, No. 5 
error in the determination of the metabolizable energy 3 cause 
more or less variation in the values per unit of feed in the different 
periods. Such variations may seriously affect the net-energy values 
computed by this method. If, for example, one assumes a difference 
in the metabolizable energy per pound of dry matter of the hay of 
only 50 Calories between the two periods, witnout changing the aver¬ 
age metabolizable-energy value, the data of Table I, Part A, would 
be changed into those of Part B, or of Part C. 
EXAMPLE 1 
Table I .—Computation of net-energy value of timothy hay 
PART A 
Dry 
matter 
of hay 
eaten 
Metabolizable 
energy 
- 
! Gain of 
duced ! ener ey 
■' 
i 
| 
I 
Per 
pound 
dry 
matter 
Total 
Period 4_ 
Lbs. 
10.21 
6.17 
Cals. 
935 
935 
Cals. 
9,544 
5,768 
Cals. ! Cals. 
9,812 -268 
8,064 -2,296 
Period 3__ __ 
Difference_ 
4.04 
3,776 
935 
1,748 i 2,028 
433 1 502 
1 
Difffirfince ner nound drv matter of hav 
_ 
1 1 
PART B 
Period 4______ 
10.21 
6.17 
910 
960 
9,291 
5,923 
9,812 
8,064 
-521 
-2,141 
Period 3_____ 
Difference_ 
4.04 
! 3,368 
834 
1,748 
433 
1,620 
401 
Difference per pound dry matter of hay__ 
PART C 
Period 4. _ _ 
10.21 ! 960 
6.17 j 910 
9,802 
5,615 
9,812 
8,064 
-10 
-2,449 
Period 3_ 
Difference_.._ 
4.04 1 . 
4,187 
1,036 
1,748 
433 
2,439 
' 603 
Difference per pound dry matter of hay... 
In Table I, Part B, the metabolizable energy per pound of dry 
matter of the hay eaten is 910 Calories in period 4, ana 960 Calories 
in period 3; the average being 935 Calories as in Table I, Part A. 
The apparent net-energy value of the hay per pound of dry matter is 
1,620-^4.04 = 401 Calories, or 834 — 433 = 401 Calories, instead of 
502 calories—a difference of 101 Calories, or 20 per cent. This 
difference in net-energy value is the direct result of the assumed 
difference of 50 Calories in the metabolizable energy per pound of dry 
matter of hay of the two periods compared, although the average 
metabolizable-energy value of the hay, and heat increment, remained 
unaltered. The metabolizable energy per pound of dry matter of 
the added hay is 834 Calories, which is considerably less than the 
value of the hay eaten in either period 3 or period 4. 
* For some sources of error in the determination of metabolizable energy see (II). 
