366 VETERINARY PHYSIOLOGY 



The loss in the pig is comparatively small. In the horse 

 fermentation occurs in the caecum and colon after the food 

 has passed through the small intestine. Consequently, it is 

 chiefly the crude fibre, the constituent that has resisted the 

 digestive processes that is affected. 



Factors affecting Availability — ( 1 ) Species.— Concentrates are 

 equally well digested by all farm animals. Differences occur 

 in the availabilitv to digest fodders, or other food-stuffs 

 containing much crude fibre. These are utilised more com- 

 pletely by the ruminant than by the horse. The following 

 table shows the average percentages of the constituents of oats 

 and hay digested by the horse and the sheep : — 



The pig digests pure cellulose well, but owing to the lack 

 of a macerating compartment like the rumen of the ox or 

 the Cfecum and colon of the horse, fibre with encrusting 

 material in it is very incompletely digested. Of the crude 

 fibre of ordinary feeding-stuffs it digests little more than 

 50 per cent, of the amount digested by the ruminant. 



(2) Amount of Food. — -The availability of the food is 

 little affected by the amount eaten unless on heavy mixed 

 feeding with fodder and concentrates, in which case the 

 percentage digested is decreased. The decrease is due to the 

 too rapid passage of the food through the alimentary tract. 

 On feeding with fodder alone, however, the results of 

 experiments show that the amount eaten makes no appre- 

 ciable difference on the percentage digested. 



(3) Cooking and Grinding. — Starchy foods like potatoes 

 are more completely digested after cooking. With this 

 exception cooking usually decreases the percentage digested, 

 proteins being especially affected. 



For horses and swine the digestibility of grain is 

 increased by crushing, and still more by grinding. In 



