RELATIVE VALUES OF FEEDING STUFFS 619 



age results for total organic matter and for nitrogen-free extract are 

 fairly uniform in each series of experiments, although there was some- 

 what more variation in the individual trials, and fail to give any 

 decided indication of a diminished digestibility with the increasing 

 amounts of roots consumed. The computed digestibility of the crude 

 protein is more or less variable, but on the whole a decreased diges- 

 tibility of this ingredient as the proportion of roots to hay increased 

 seems to be plainly shown. 



It is, of course, impossible to determine in a digestion experi- 

 ment in which roots are added to a basal ration what propor- 

 tion of the fecal matter is derived from the roots and what from 

 the remaining ingredients, and such results as those of Wolff 

 may be interpreted either as showing a fairly constant diges- 

 tibility of both the hay and the roots (aside from crude protein), 

 or, on the assumption of complete digestibility of the roots, as 

 showing a progressive depression in the digestibility of the 

 hay. To the writer, the former appears on the whole the more 

 reasonable course, although it should be added that in some of 

 the experiments the absolute amount of crude fiber in the feces 

 was increased by an amount greater than that contained in the 

 roots consumed, thus demonstrating a depression of the diges- 

 tibility of this constituent of the hay. Probably the truth 

 lies between the two views. It is unlikely that roots are en- 

 tirely digestible and, on the other hand, it is probable that a 

 large proportion of them may diminish to some extent the di- 

 gestibility of other feeding stuffs consumed with them. It is 

 to be remembered, however, that roots contain not altogether 

 inconsiderable quantities of crude protein which, as shown in a 

 following paragraph (727), tends to offset the effects of their 

 carbohydrates. 



725. Cause of diminished digestibility of protein. Atten- 

 tion has already been called (163-167) to the influence of the 

 excretory products contained in the feces on the apparent diges- 

 tibility of the nutrients and especially of protein. According 

 to Kellner's and Pfeiffer's results, the digestion of each 100 

 grams of dry matter, whether protein or nitrogen-free material, 

 results in the excretion in the feces of approximately 0.4 gram 

 of nitrogen in the form of these excretory products. If, then, 

 a kilogram of dry starch be added to a basal ration, the nitrog- 

 enous excretory products in the feces are increased by ap- 



