234 Agricultural Chemistry. 



rates, as potatoes and mangels, cannot be given in greater pro- 

 portion than 15 per cent of the fodder (both calculated as dry 

 food) without diminishing the digestibility of the latter. 



Lindsey of the Massachusetts Station has, in part, confirmed 

 the work of Dietrich and Koenig. He found that when Porto 

 Rico molasses fed together with hay, constituted from 10 to 15 

 per cent of the total dry matter of the ration, little if any de- 

 pression occurred. But with molasses constituting 20 per cent 

 of the dry matter of the ration, a depression of 4.5 per cent was 

 noted in the digestibility of the hay. He concluded that molasses 

 and hay would not make a satisfactory combination for farm 

 stock. A more suitable ration would consist of hay, together 

 with one or more protein concentrates and molasses. Even in a 

 ration of hay and gluten feed and in which molasses composed 

 20 per cent of the dry matter, there was a depression of 8 per 

 cent in the digestibility of the hay and gluten. 



The nutritive ratio. We have seen that the formulation of 

 feeding standards must be based on a knowledge of the relative 

 digestibility of the several nutrients contained in the feeding 

 material. Such knowledge has been secured by many experi- 

 menters, working with various classes of farm animals, and has 

 given us our tables of co-efficients of digestibility available in 

 books on animal feeding. (See table in Appendix.) 



It has been found in practice that the feed of an animal may 

 be varied within fairly wide limits, provided the ratio of digest- 

 ible protein to all other digestible organic matter is kept within 

 certain limits. Protein has special and peculiar functions and 

 less than a certain minimum would limit production by just the 

 amount of the deficiency. In order to get this ratio it is neces- 

 sary that some carbohydrate be taken as a standard for express- 

 ing the non-protein portion of the ration. Starch is the sub- 

 stance always chosen, and it becomes necessary, in order to ex- 

 press the fats and other carbohydrates in terms of starch, to ob- 

 tain the equivalent in heat producing power of the other food 

 constituents. This has been secured (1) by burning a weigher! 



