FACTORS FOR CALCULATING FOOD VALUES. 13 



must be used, and the real available energy of the food is therefore 

 equivalent to the metabolizable energy, or gross available energy, less 

 the eneiL r \ expended during the eating and digestion. 



PRODUCTION VALUE. 



The finally available energy of the food may be of value in two ways, 

 depending >n the object for which the animal is fed. It may be de- 

 sired simply tn prevent the loss of flesh or energy, i. e., the object 

 may be to maintain the animal in all respects in a certain desirable 

 condition. Food given for such a purpose is known as a "mainte- 

 nance ration." and each of the nutrients has a value as a part of such 

 a ration, which value can only be determined by experiments on ani- 

 mal-, for it has bem found that the metabolizable energy and the 

 energy as maintenance are not equal. This work has been, done by 

 Arm>l>y." \\ h.t found in general that 62.92 per cent of the metaboliz- 

 uhle energy of < l..\< r hay was available for maintenance. 



On the other hand, a ration may be fed to animals for the purpose 

 of producing increase in flesh, and consequently more than a main- 

 tenance rat ion HUM l>eu r i\en. In this case, that part of the food that 

 i> in of \\hat i- required for maintenance is used by the animal 



for increase in lle>h and has a definite value as such. In experiments 

 to determine the value of a given food for producing flesh, the mate- 

 rial ix IV d in addition to a basal maintenance ration and its value 

 deteniii' icasured by the gain in flesh produced. The value so 



found has been termed the /n'm/nrfitui mine, of the food. Kellner 6 

 ha- determined i hoe production values for the pure. nutrients when 

 fed in addition to a basal maintenance ration to mature fattening 

 cattle. He found that while the ratio of the nutrients to each other 

 remained nearly the -ame the actual values for production are only 

 about one-half the met aholi/able values. 



. \ I ,',,,,, n,.tnhnli:nM,- t'iu'n/ii and production value of nutrients per 



pound. 



The most direct and the simplest method of expressing this pro- 

 duction value is in Calories per pound or per 100 pounds, as is done 

 by Annsby in recent publications of the Pennsylvania agricultural 



iiisylvuiiia Agr. Exp. Sta. (1905), Bui. 71, p. 12. 

 &Loc. <-it., p. 153. 

 cLoc. cit. 



