60 Report of Department of Animal IIu5BA^DKY. 



The foregoing figures are instructive in showing approxi- 

 mately how the energy of the rations was utilized bv these two 

 milch cow^s. After accounting for the energy of maintenance on 

 the basis of the best knowm data, viz: 13,000 Calories for an 

 animal weighing 500 kilos (1100 lbs.) and the energy of the milk 

 solids, we have a balance amounting on the average to about 

 one-quarter of the available energy of the ration. If the ration 

 were diminished to the extent of this balance it would certainly 

 result in a lessened milk yield, consequently we are justified in 

 concluding that this balance has some necessary function or 

 relation in milk secretion. 



The most natural and logical conclusion is that in part at 

 least it sustains the work of milk secretion, i. p., the vital 

 activity involved in the metabolic changes occurring in the milk 

 glands or elsewhere in the formation of milk solids. There is, 

 of course,*more work demanded for mastication and digestion 

 than is the case with the much smaller maintenance ration. 

 Nevertheless it is fair to regard the milch cow as a working 

 animal, not in the exercise of mechanical force but in the main- 

 tenance of manufacturing processes which are sustained by the 

 application of the quiet energies of life. 



