38 SCIENTIFIC FEEDING OF ANIMALS 



quence of this, more of the nutrients of the hay 

 would pass into the faeces, that is, less would be 

 digested than when hay alone was fed. Be that as 

 it may, the fact remains that the digestibility of a 

 food poor in protein is diminished when large 

 quantities of easily digestible nitrogen-free sub- 

 stances of the kind already mentioned are mixed 

 with it. 



4. The addition of fat or oil does not alter the 

 digestibility of a food, provided the added material 

 is in a finely divided form, and moderate quantities 

 (not more than 1 lb. per 1000 lbs. body weight) only 

 are given. If, however, large quantities of oil or 

 melted fat are poured over the food, its digestibility 

 is diminished. This is due to the difficulty with 

 which the digestive juices penetrate the particles of 

 food which are coated with oil. In the natural 

 food-stuffs the oils and fats are always present in 

 the form of microscopically small globules. 



5. The increase of crude protein in a food causes 

 not only no depression of digestibility of the other 

 components, but, on the contrary, minimises the 

 depressing effect of large quantities of nitrogen- 

 free substances. If, for example, ruminants are 

 being fed with a mixture of hay or straw and a lot 

 of potatoes, then, as has been shown (p. 36), the 

 nitrogen-free substances are not completely digested, 

 in fact, part of the easily digestible starch passes 

 into the faeces. When a food rich in protein — 



