Feeding Standards. 235 



portion of the various materials in a calorimeter (an instrument 

 for measuring heat production), and (2) by direct experiments 

 upon animals placed in a respiration calorimeter (an apparatus 

 for measuring both gas and heat production) , and fed with known 

 weights of the various feeding-stuffs. As an average of several 

 experiments it may be taken that one part of fat evolves as much 

 heat as 2.4 parts of starch, sugar, cellulose or of protein. To 

 express the non-protein, other than carbohydrates, in terms of 

 starch, it is therefore necessary to multiply the quantity of di- 

 gestible fat by 2.4 and add this product to the quantity of digest- 

 ible carbohydrates present. The nutritive ratio thus becomes : 



digestible protein 



digestible carb. + (dig. fat X 2.4) 

 The nutritive ratio of corn meal is obtained as follows: 



100 Ibs. contain 7.9 Ibs. digestible protein 



66.7 Ibs. digestible carbohydrates 

 4.3 Ibs. digestible ether extract (fat) 



7.9 7.9 7.9 1 



66.7 + (4.3 X 2.4) 66.7 + 9.32 76.02 9.6 



The nutritive ratio for corn meal is therefore 1 :9.6. This 

 means that for every pound of digestible protein in corn meal 

 there are 9.6 pounds of digestible carbohydrates and ether ex- 

 tract (fat) equivalent. The term "wide" ratio is used when 

 there is a very large proportion of carbohydrates contained in a 

 feed in proportion to the protein. Oat straw, with a nutritive 

 ratio of 1:33.7, is an example of a very "wide" nutritive ratio. 

 With corn the ratio is "medium," while with oil meal, with a 

 ratio of 1:1.7 the expression "narrow" is used. 



The Wolff-Lehman feeding standards. In 1864 Wolff pro- 

 posed certain feeding standards, which have been largely used in 

 framing rations. In order to eliminate the size of the animal, 

 'the proportion of the various feed constituents, to be supplied 

 daily for 1000 pounds of body weight, are given. For illustra- 

 tion, a few standards are given here. (See full table in Ap- 

 pendix.) 



