912 EXPERIMENT STATION RECORD. 



The urine contained 96.2 gin. of nitrogen; tlie milk contained 50.9 

 gin. of total nitrogen, 47 gm. of albuminoid nitrogen, 335 gm. of fat, 

 and 490 gm. of milk sugar. Deducting the nitrogen in the urine 

 and milk from the amount digested shows that there was a gain of 

 19.7 gm. of nitrogen. As noted above, the cow digested 1,040 gm. of 

 crude fiber, in addition to the protein, fat, and carbohydrates. Accord- 

 ing to previous statements, 924 gm. of crude fiber was required for 

 maintenance (0.44x2,100=924), therefore 110 gm. (1,040-924 = 110) of 

 crude fiber was digested in excess of the amount required, and had no 

 nutritive value because it was fermented, yielding carbon dioxid, water, 

 and heat, the latter only being of use to the body. This necessitated 

 an expenditure of 10 per cent of the total energy of digestion, on the 

 supposition ordinarily made, and leaving out of account the fact that 

 the energy derived from crude fiber merely covers the labor of chewing 

 and digesting it. 



On the basis of the nitrogen excreted in the urine, 577 gm. of protein 

 (96.2x6.25=577) was required for maintaining the animal. Deducting 

 this amount from the total ainouut consumed leaves 422 gm. for milk 

 produced and flesh gained. Some idea of the amount of nitrogen-free 

 extract which was required for maintenance may be obtained from the 

 following: The fuel value of digestible protein is 4.1 calories per gram, 

 of starch 4.1S calories per gram. The two substances have practi- 

 cally the same value. An animal weighing 1,000 kg. requires 5.2 kg. 

 (0.7 -f- G.0— 2.1 (crude fiber) =5.2) of protein and nitrogen-free extract 

 for maintenance. An animal weighing 440 kg. would therefore require 

 440x5.2=2,2S8 kg. As noted above, 577 gm. of protein was necessary 

 for maintenance; therefore the nitrogen-free extract must have been 

 equal to 1,711 gm. (2,288—577=1,711). The cow digested a total of 

 4,306 gm. of nitrogen-free extract. Deducting the 1,711 gm. necessary 

 for maintenance, there remains 2,595 gm. Of this amount 24.1 per cent, 

 or 025 gm., would be lost by the fermentation which takes place in 

 the intestines, leaving 1,970 gm. of nitrogen -free extract available 

 (2,595-025=1,970). 



The labor of digestion would require 10 per cent of the 442 gm. of 

 protein, 327 gm. of fat, 2,595 gm. of nitrogen-free extract, and 116 gm. of 

 crude fiber (the amount previously calculated to be in excess of that 

 required for maintenance). The amount of protein metabolized is 

 shown by the excretion of nitrogen in the urine. Furthermore, as 

 noted on p. 816, nitrogen-free extract can take the place of fat in the 

 ratio of 44: 107, i. c, 2.4. Hence, the value of a ration can be calcu- 

 lated in terms of nitrogen-free extract, or "nutrients" in the sense in 

 which Wolff used the term, giving 442 + (327x2.4) + 2,595+116=3,838 

 gm. of nutrients. Deducting 10 per cent of this amount, or 384 gm. 

 from the 1,970 gm. of nitrogen-free extract, there would remain 1,58G 

 gm., which may be assumed to be starch, sugar, or similar carbohy- 

 drates. Therefore the cow had at her disposal for milk production 



