176 Tlie Feeding of Animals 



starch on a purely theoretical basis as Hemieberg did 

 some years ago, it would appear that 100 parts of body 

 fat can be obtained from 194 parts of albuminoids or 

 244 parts of starch. The fat factor of albuminoids 

 would be therefore 51.4% and of starch 41%. The 

 equivalence of food fat in terms of body fat has never 

 been expressed on such a basis, though it is customary 

 to assume that the fat of the food may cause the pro- 

 duction of an equal quantity of body fat or milk fat, 

 an assumption which has no foundation whatever. 



These theoretical figures are an attempt to show 

 Avhat protein and starch may do when actually used 

 for storage purposes. They cannot be accepted as 

 meaning much in indicating how the food is really 

 used in practice. It is probable that the excess of 

 food over and above maintenance is never all used 

 for production according to the theoretical possibilities 

 based upon chemical rearrangements of compounds. 

 Certainly the production from a given quantity of 

 food varies greatly under unlike conditions. It can 

 scarcely be doubted that the proportion of the avail- 

 able nutrients which are consumed, that is, burned as 

 fuel, increases as the ration increases above what is 

 needed for maintenance, and inversely the proportion 

 of the nutrients stored in the body as flesh and 

 fat is less the greater is the quantity fed in excess 

 of the demands for maintenance. A large excess over 

 maintenance is relatively less efficient than a small 

 one. There comes a point where additional food pro- 

 duces no additional gain, but only additional consump- 

 tion. The age of the growing animal and the condition 



