4:20 THE FEEDING OF ANIMALS 



products. The latter is the important ratio to consider 

 if we are seeking to learn how we can most eflBciently 

 apply farm crops to the sustenance of the human family. 



509. Factors involved in food economics. — ^This study 

 of food economics requires a knowledge of several factors. 

 In the first place, we must have the information coming 

 from feeding experiments, where a careful record has 

 been kept of the kind and amount of food consumed and 

 the weight of the resulting growth, milk, eggs, or what not. 

 This information must be supplemented by a knowledge 

 of the digestibility of feeding-stuffs, of the ratio between 

 the live animal or other gross product and the commer- 

 cial products, and of the composition and proportion of 

 edible material supplied by the commercial article. For 

 instance, we find it takes, on the average, 7.4 pounds 

 of digestible organic substance in the ration to produce 

 1 pound of growth in a steer, and we have learned by 

 slaughter tests that the average per cent of carcass for 

 97 animals was 61.4, and by the butchers' and chemists' 

 analyses, that the carcass contains an average of 33.2 

 per cent of edible dry matter. From these data it is easy 

 to calculate that 12 pounds of digestible food are needed 

 for the growth of 1 pound of carcass or 36.3 pounds for 

 the growth of 1 pound of edible beef solids. 



510. Relation of food to production with various 

 species. — ^The following tables give the data upon which is 

 based the productive power of food when utilized by 

 the various classes of animals. Data of this kind are 

 practically our only means of studying the economics 

 of producing those human foods which are most cosily 

 in proportion to their nutritive value, a study which is 

 very important wherever it becomes necessary to econo- 

 mize energy. It shows the coefficients of efficiency of 



