134 PRINCIPLES OF ANIMAL NUTRITION. 
which case we might expect a proteid supply equal to the fasting 
proteid metabolism to be sufficient to produce nitrogen equilibrium. 
Seen in this light, the apparently insignificant effect of the non- 
nitrogenous nutrients becomes a very important factor in nutrition. 
The effect of the non-nitrogenous nutrients in largely diminish- 
ing the necessary proteid supply was pointed out by C. Voit * and 
appears clearly in many of his experimental results. Thus from the 
summary on p. 95 it appears that from 1200 to 1500 grams of lean 
meat per day was required to maintain the animal experimented 
upon in nitrogen equilibrium. When fat or carbohydrates were 
added to the ration, however, strikingly different results were 
reached, as appears from the following comparative statement, 
the results being expressed as “ flesh” with 3.4 per cent. of nitrogen: 
Food. 
ies. Gain vot 
Fat | bolized. een 
a ae eo 
SOO |v eecinieuss 416 —116 
600 | ....... 674 — 74 
Meat only (average of both series). GOO) | ewivede eens 943 — 43 
1200 | ....... 1207 — 7 
1500 | ....... 1478 + 22 
500 250 444 + 56 
Meat and fat .................. 800 200 720 + 80 
1000 250 875 +125 
500 300-100 502 -—- 2 
Meat oc (compare 800 100-400 763 4 37 
Ps L1G)-.ccde sehen ca weal 1000 100-400 902 + 88 
In the presence of non-nitrogenous nutrients, nitrogen equi- 
librium was reached with quantities of proteids from one third to 
one half as great as the amount required when fed alone. In other 
words, the non-nitrogenous nutrients materially reduced the mini- 
mum of food proteids required to maintain the proteid tissues of 
the body. 
In view of the peculiar importance of the proteids in nutri- 
tion, as well as of their relative scarcity and high cost, particu- 
larly in the food of our domestic animals, great interest attaches 
to a determination of the least amount required to sustain a mature 
* Zeit. f. Biol., 5. 
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