6 N. H. EXPERIMENT STATION [Bulletin 205 



animal must have a certain amount of protein, fat, carbohy- 

 drates, water and mineral constituents. In addition there 

 are other things, known as "vitamines", "growth promoting 

 substances", or "food accessories", the chemical nature of 

 which is not well understood, which are necessary. The 

 latter substances, however, are usually present in sufficient 

 quantities in our regular feeding-stuffs if we feed a suffic- 

 ient variety and we need not consider them. Our feeding- 

 stuffs contain mineral matter sufficient for the needs of an 

 animal with a few exceptions, such as calcium carbonate 

 which we furnish as oyster shells for hens, salt, and phos- 

 phorous and calcium which is sometimes fed to dairy cattle 

 in bone meal so we need not consider the mineral matter 

 further. 



The Protein, fat and carbohydrates must he furnished in 

 the feed and it is their content ivhich largely determines the 

 value of the feed. 



DIGESTIBILITY IMPORTANT IN DETERMINING 

 THE VALUE OF FEED. 



When fed not all of the protein, carbohydrates and fat in 

 the different feeding-stuffs are digested. In comparing the 

 value of the different feeding-stuffs, especially when they 

 are of different types, we must take into consideration the 

 digestibility of these food nutrients. The coefficient 

 of digestibility is a term which expresses the percentage 

 amount of the food nutrients which are digested and 

 absorbed by the animal. Table Number 3 gives a summary 

 of the average results for some of our common feeding- 

 stuffs. 



