122 THE FEEDING OP ANIMALS 



The foregoing statements make it plain that when the 

 general composition of a food is known, it is possible to 

 predict with a good degree of certainty whether its per- 

 centage of digestibihty is high or low. Feeding-stuils 

 with a high percentage of starch and sugar and a small 

 percentage of fiber have a relatively high digestibility, as, 

 for instance, com meal, while the coarse foods like timo- 

 thy hay and straw, with a high proportion of gums and 

 fiber, have a relatively low digestibility. 



FACTOHS WHICH MAY INFLUENCE DIGESTION 



Digestion has an important relation to the nutritive 

 efficiency of food because only that portion of the food 

 that is digested and absorbed can serve the purposes of 

 growth and the maintenance of the vital functions. 



180. Meaning of "digestibility." — ^In discussing the 

 factors that may influence the digestion of food, it is 

 essential to understand clearly what is involved in the 

 term digestion as it is used in science and in common 

 speech. This term includes at least two elements, com- 

 pleteness of solution of the food nutrients and rate of 

 digestion. The figures that are given for the digestibil- 

 ity of various cattle foods refer to the completeness or 

 extent to which the food is dissolved and transferred to 

 the circulation. But different foods from which come the 

 same proportion of imdigested dry matter may differ 

 materially in the rate at which they imdergo digestive 

 changes, and in this sense their digestibility is unlike. 

 The ultimate completeness of solution in the digestive 

 fluids may not be influenced by the rate at which the 

 process goes on. 



