New Yokk Agricultural Experiment Station. 667 



able to the animal in furnishing material for bone structure and in 

 the formation of the soft tissues of the body. 



Protein is the nitrogenous part of a feed ; and is of great importance 

 as it forms muscle, ligaments, hair, hide and bones in the animal 

 body. It is also a source of energy under all conditions of nutrition, 

 and in case a proper proportion of carbohydrates and fats is not main- 

 tained in the ration, its use as a source of energy may be greatly 

 increased. 



Fat (or Ether extract) is that portion of a feed which is soluble in 

 ether. It is composed chiefly of oils and fats, and may contain in 

 addition a large amount of resinous substances and coloring matter. 

 The oils and fats contained in this extract may be utilized by the 

 animal for the production of fat and energy. 



Fiber is the woody matter which forms the framework of plants. 

 It is considered the most indigestible part of a feed. 



Nitrogen-free extract consists of non-nitrogenous bodies such as 

 starches, sugars, gums, vegetable acids, etc., and is useful in supplying 

 fat and energy. It is not ordinarily determined by chemical anal- 

 ysis but is obtained by subtracting the sum of the percentages of 

 moisture, ash, protein, fat and fiber from 100. 



The nitrogen-free extract and crude fiber taken together are termed 

 " carbohydrates." 



DIGESTIBILITY AND NUTRITIVE RATIO. 



The groups just described constitute the nutrients of a feeding 

 stuff. Before any of these substances can be used by the animal, 

 it must be dissolved by the action of the digestive juices of the 

 mouth, stomach and intestines. This process of solution is called 

 digestion. It should be understood that the constituents of no cattle 

 food are entirely digested, and that owing to the composition of the 

 material, appreciable quantities are wasted. 



The percentage of a nutrient which is removed from a food by 

 digestion is called the "Digestion coefficient," or the ''Percentage 

 of digestibility. '' 



Digestion coefficients for many of the grains, grain by-products and 

 fodders have been determined by repeated experiments. 



In order to determine the quantities of " Digestible nutrients " in a 

 food it is necessary to multiply the percentage of protein, fat, fiber, 

 etc., by the digestion coefficient of each nutrient. For example, if a 

 gluten feed contains 24 per ct. of protein, which has a digestion 

 coefficient of 85.6, the material would contain (85.6 X 24) -r- 100 

 or 20.5 lbs. of digestible protein in 100 lbs. of feed. A similar 

 process is necessary for each of the other nutrients. 



The Nutritive ratio of a feeding stuff is the rt-lation in quantity 

 between the digestible nutrients which it contains. By this term 

 is meant the relation of the digestible protein to all the other diges- 



