io8 THE CHEMISTRY OF CATTLE FEEDING 



this, no difference has been observed as between the different 

 breeds of the same kind of animal. Within limits, the age of 

 the animal has no effect upon the digestibility of the food ; 

 and, contrary to what is often supposed, the coefficients are 

 practically the same when the animals are at work as when 

 they are at rest. 



Since the processes of digestion are caused by ferments, 

 anything which inhibits or interferes with their action must 

 tend to reduce the digestibility of the foods. Excess of common 

 salt is the only substance likely to produce such effects. No 

 other antiseptics are ever added to cattle foods. They are not 

 required. 



A certain amount of water is required to form the digestive 

 juices, to dissolve the products, and for other purposes ; but if 

 a large quantity is drunk immediately before or after a meal, 

 it may tend to interfere with gastric digestion by unduly 

 diluting the gastric juice and by temporarily lowering the 

 temperature of the stomach. 



Condiments and spices of various kinds are said to increase 

 digestibility. These substances are not, themselves, digestive 

 agents, but they may tend to increase the flow of digestive 

 juices in the mouth and stomach. They are probably 

 advantageous in fattening chiefly as a means of inducing the 

 animals to consume more food. For this purpose, sugar and salt 

 in moderate quantities are amongst the most useful condiments. 



The digestibility of green fodders is not affected by drying, 

 e.g. by making grass into hay, provided that no loss occurs in 

 the process. The dried products are, however, more difficult 

 to masticate than the fresh, juicy material, especially if the 

 plants are old and contain much fibre, and a certain loss of 

 energy is involved (p. 154). 



Metabolism. The constituents of the food which are 

 absorbed by the villi (p. 102) undergo further changes within 

 the walls of the intestines ; but these changes are of a reverse 

 kind. Substances of more complex character are regenerated 

 out of the comparatively simple products to which the original 

 constituents of the food are reduced by the processes of 

 digestion. Probably proteoses, peptones, and possibly also 



