86 SCIENTIFIC FEEDING OF ANIMALS 



be used as a basis upon which to calculate rations. 

 The productive value of the nutrients has to be 

 considered, and this can vary a great deal, as is 

 shown from the comparison of the oil-cake meals 

 and the coarse fodders. 



Attention has already been called (p. 20) to the 

 fact that the work of mastication and of digestion 

 is not by any means small in the case of coarse foods. 

 To obtain definite information on this point, straw 

 was fed in one case as coarse chaff and in the other 

 in a finely ground form. It was found that the 

 finely ground straw which did not require to be 

 chewed was considerably better utilised than the 

 chaff. The decrease in productive value was, in 

 fact, on an average 50% greater in the case of the 

 chopped straw than in the case of the finely ground 

 straw. The improvement due to grinding was 

 greater with the wheat straw than with the barley 

 or oat straw, and experiments with wheat chaff 

 showed that the limit of improvement is reached 

 when the particles of ground straw are about as 

 large as in the chaff. As the grinding of the straw 

 only partly reduced the bad results noticed in the 

 case where it was chopped, there must be some 

 other cause in addition to the difficulty of mastica- 

 tion. Experiments where sawdust was added 

 to the ration have indeed shown that this slightly 

 digestible material depresses the digestibility of 

 the other food'. 



