54° PRINCIPLES OF ANIMAL NUTRITION. 
at 4.1 Cals. per gram. As we have seen, however (Chapter X), 
this figure is probably too high for herbivora, although exact figures 
for the horse are not yet fully available. Approximately, however, 
we may estimate the metabolizable energy of the several digested 
nutrients as follows (p. 332): 
Pr6tells: 2p.s sia ek wee ee 3.228 Cals per gram 
Crude fiber. ............00 00 B6b2a Mes 
Nitrogen-free extract.......... AN85- SE SE oe 
Ether extract..............005 Bvol2) Se FE 
Zuntz * estimates the metabolizable energy of the total nutri- 
ents (including fat X 2.4) at 3.96 Cals. per gram. This figure is 
probably somewhat high, especially for rations containing much 
crude fiber or ether extract, but may serve the purpose of approxi- 
mate calculations. 
EXPERIMENTS ON SINGLE FrEpING-sTuFFs.—Comparatively few 
of the experiments admit of a direct computation of the utiliza- 
tion for a single feeding-stuff, since in most cases the amounts of 
two or more feeding-stuffs were varied simultaneously. As an 
example of the former class we may take Periods I and II of the 
experiments of 1892-93. In Period I the ration consisted of 7.5 kgs. 
of hay and 4 kgs. of oats per day, while in Period II the oats were 
increased to 5.5 kgs. The quantities of nutrients digested and the 
metabolizable energy of the difference between the two rations 
(computed by the use of the factors just given) were— 
i Crude Nitrogen= Ether Total 
Protein, : fi Ue 
Gems, | Ger | Megtenet, | gtzets | Nutrients, 
Period II....... 1022.4 849.6 4152.8 175.8 6446.6 
a > Nea toad Jasenieas 847.8 819.9 3598 .4 137.1 5595.3 
Difference .... 174.6 29.7 554.4 38.7 851.3 
. Cals. Cals. Cals. Cals. Cals. 
Equiv. energy... 564 105 2320 332 3321 
In Period I (20 days) the daily work consisted of 300 revolutions 
of the dynamometer. With this amount of work the live weight 
of the horse underwent very little change, but there was a material 
* Landw. Jahrb., 27, Supp. III, 418. 
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