332 PRINCIPLES OF ANIMAL NUTRITION. 
implied in this that the metabolizable energy of the digested nitro- 
gen-free extract is the same as its gross energy. 
Summary.—The results recorded in the preceding paragraphs 
regarding the metabolizable energy of the several classes of digesti- 
ble nutrients are summarized in the following table: 
METABOLIZABLE ENERGY OF DIGESTIBLE NUTRIENTS. 
Cattle, Horse, |' Swine, 
Cals. per Cals. per Cals. per 
Grm. Grm. Grm. 
Protein (N X6.25) : 
From wheat gluten .................00- 4.894 
“ AN KSe7) cccaccesawss 4.958 
“beet molasses...............0005- 3.984 
«mixed grain ..............000- Se cetlill a (vane ater ats [incre Ae ool 4.083 
ef “ration of oats, hay, and straw 3.228 
«meadow hay ...........00eceeeee 1.272 
“ timothy hay .................05. 3.057(?) 
FESS GR AW) Sunder x cer piete tos was Mie ord we tues (?) 
Fat: 
From peanut oil..............00 0c ee eee 8.821 
«hay (ether extract)............005 8.322 
Carbohydrates : : 
Starch, Kellner’s experiments Seng euaeer gia Ses 3.763 
« ~ Kithn’s he | ee adanete aa 3.648 
pee extract (assumed) .........]......... 4.185 
Crude fi ber, of extracted straw .......... 3.606 
“ hay fed alone............. 3.311 
s «« «added to basal ration . 3.606 
se “© oat straw ........0 0c eee 3.437 
ar « “ wheat straw ............. 3.001 
af «© mixed ration ............/...00000, 3.523 
Perhaps the most striking thing about these figures is the wide 
range of the results upon the same class of nutrients. For reasons 
already stated, this is most noticeable with the protein, but it is 
sufficiently marked also with the other two groups. Moreover, 
such meager data as we possess regarding other animals than the ox 
indicate that the results vary with the species of animal, a fact 
which should not surprise us, but which, nevertheless, adds mate- 
rially to the complexity of the subject and greatly widens the range 
of necessary investigation. It is obvious, therefore, that at present 
our knowledge is too imperfect to allow of the assignment of average 
values for the metabolizable energy of the different classes of 
