VALUATION OF FEEDING-STUFFS 285 



of which would be about one cent, when we pay $30 a 

 ton for the cottonseed meal. On this basis it would be 

 necessary to assign to the protein a cost of two cents per 

 pound, and to the fats three cents. If our premise were 

 correct we could calculate the cost of the nutrients in any 

 one of the feeding-stuffs, and could either ascertain which 

 was the cheapest source of each ingredient, or by aver- 

 aging could establish a basis for a general valuation. 

 Unfortunately no such a premise can be correctly formu- 

 lated. We are not yet wise enough to establish fixed 

 relative physiological values for the three classes of 

 nutrients. 



381. Energy values as a basis of valuation. It may 

 be stated that the energy values of a unit of each of the 

 nutrients, protein, starch, and fat have been found with 

 apparent accuracy. Why, then, may we not establish 

 the relative value of the nutrients on the basis of their 

 potential energy, which is measured by the heat they pro- 

 duce upon combustion? Simply because foods have 

 another function beside furnishing motive power to the 

 animal and keeping him warm. They act as building- 

 material. The protein and fat of milk and of the body 

 tissues are derived from the food compounds, and the 

 actual relative money value of these compounds for con- 

 structive purposes is not yet known. No one has yet suc- 

 ceeded in actually determining the relative money value 

 of protein, carbohydrates, and vegetable fats as fat pro- 

 ducers, and we have no data that allow a definite conclu- 

 sion concerning the comparative money worth of the 

 muscle-forming function of protein as against the fat- 

 forming function or energy function of starch. There is 

 no promising prospect, at present, of being able to com- 

 pare foods on the basis of their physiological importance 



