FACTORS FOR CALCULATING FOOD VALUES. 11 



utilized by the animal has been termed available energy or, better, 

 metabolizable energy." 



The loss of energy due to waste products other than undigested 

 food varies with different animals and with each of the nutrients, so 

 that the corrections necessary can only be made after direct experi- 

 ment. Such experiments have been made upon carnivorous animals 

 (dog.o by Kiibner, and his results giving the available or metaboliz- 

 able energv <>t' each of the three groups of nutrients have been accepted 

 and applied to other animals as well. Within recent years, however, 

 Kellner and other- have carried out experiments with other animals, 

 especially herbivorous animals, and it has been found that the figures 

 given by Riibner for dogs do not apply to herbivorous animals. 

 Ivellner's work was with mature fattening cattle, and the following 

 table gives the total calorific value and metabolizable energy in 

 Caloric- per pound for each of the three groups of nutrients as found 

 bv Kellner and the met aboli/ab!e energy as found by Riibner. In 

 Kellner'- \\ork the eonvctions were made on the values for wheat 

 gluten as protein, on ordinary ether extract, and on starch as carbo- 

 hydrs 



TABLE IV. Metabolizable energy of nutrients per pound. 



The-e liiriuv- mean that for every pound of protein digested by 



cattle 2,720 Calories of energy are produced, but only 2,220 Calories 



really Available from the food metabolized by the animal for the 



production of energy or flesh. From the ether extract 3,780 Calories 



of cnciLTv aiv produced for every pound digested, and of this the 



entire amount represent- metabolized food. The carbohydrates pos- 



loriefl per pound of total energy, while only 1,710 Calories 



vidded by the food really metabolized. 



From Table 111 (p. 10), which gives the amount of total and 

 digest ii.li' nutrients the eneiiry yielded by the metabolized food for 

 the production .,f animal energy or flesh can be calculated. The 

 following table gives the total nutrients, digestible nutrients, and 



a Arm.^v. Prin.-ij.lr> ,,f Animal Nutrition, 1906, p. 270. 



