RELATIVE VALUES OF FEEDING STUFFS 603 



number of single trials were made. No connection could be traced 

 between the variations in digestibility and the condition of the animals. 



The writer 1 observed a similar difference in two experiments upon 

 one sheep with clover hay while the other sheep of the pair showed 

 no significant difference. In later experiments 2 in which the feces 

 of three steers were quantitatively collected daily for periods of 56 

 and 27 days on identical rations, it was shown that the digestibility 

 of the air dry matter 3 and nitrogen computed from overlapping ten- 

 day periods, varied at times from the average for the whole experi- 

 ment by amounts greater than the estimated experimental error. 

 Mumford, Grindley, Hall and Emmett 4 likewise observed distinct 

 fluctuations in the digestion coefficients obtained with cattle in suc- 

 cessive weekly periods following preliminary periods of from two to 

 four weeks. 



All the foregoing experiments were upon dry feed and the writer 

 is inclined to attribute them, to a considerable degree at least, to irreg- 

 ular voiding of the feces. 



713. Species. The differences in the anatomy of the di- 

 gestive organs of different species might naturally be expected 

 to result in differences in the extent to which the feed of these 

 species is digested. This is true especially of those ingredients 

 of the feed whose so-called digestibility is due to the action of 

 organized ferments and which, therefore, will be more or less 

 dependent upon the opportunities which the digestive tract 

 affords for the stagnation of the feed and so for the activity 

 of these organisms. 



714. Species of ruminants. Few direct comparisons of 

 the digestibility of the same feeding stuff by different species 

 of ruminants are on record. In view of the similarity of the 

 alimentary canal in these species, one would naturally expect 

 to find comparatively small differences in the extent to which 

 identical feeding stuffs are digested. In a general way this 

 expectation is borne out by the average results of a large number 

 of recorded digestion experiments upon feeds bearing the same 

 name, although not of identical composition. Thus Wolff, 5 

 in 1874, compared the results of about 40 German experiments 



1 Amer. Jour, of Science, 28 (1885), 368. 

 2 Penna. Expt. Sta., Bui. 42 (1898), pp. 129-141. 



3 The daily excretion of dry matter was not determined and there is a possi- 

 bility of a small error due to lack of exact uniformity in the air drying. 



4 Ills. Expt. Sta., Bui. 172 (1914)- 6 Landw. Futterungslehre. 



