20 



MAINTENANCE RATIONS OF FARM ANIMALS. 



owe the unquestionable demonstration of this fact and of its signifi- 

 cance in relation to the nutritive values of feeding stuffs. 



These relations may perhaps be more clearly apprehended through 

 an illustration taken from actual experimental work. 



AVAILABILITY FOB CATTLE. 



In an experiment by Armsby and Fries 1 a steer averaging 373.7 

 kilograms live weight was fed daily 3.2 kilograms of timothy hay, 

 an amount known to be insufficient for maintenance. The potential 

 energy contained in the feed, the losses in the various excreta, and 

 the metabolizable energy of the ration were determined, with the 

 following results: 



Per day and head. 



3.199 kilos timothy liay 12. 618 



Excreta : Therms. 



4.786 kilos feces 5.247 



3.943 kilos urine .627 



0.079 kilo methane 1.057 



Total 6. 931 



Metabolizable energy of ration 5. 687 



A balance experiment with the respiration calorimeter showed, 

 as was expected, that the steer was living in part at the expense of 

 his own tissues, the total loss of protein and fat being equivalent 

 to 2.377 therms 2 per day. 



In the period immediately following this one the same steer ate 

 per day 5.194 kilograms of the same timothy hay, all the other condi- 

 tions of the experiment being as nearly identical as possible. The 

 metabolizable energy of this larger ration, determined in the manner 

 just indicated, was 9.262 therms, 3 while a balance experiment showed 

 that the loss of protein and fat had been reduced to the equivalent 

 of 0.357 therm. 3 



The following comparison of the two periods can therefore be 

 made: 



Available energy of timothy hay. 





Ration. 



Metaboliz- 

 able 

 energy of 

 ration. 



Energy of 

 fat and 

 protein lost 

 by animal. 





Kilos. 

 5.294 

 3.199 



Therms. 

 9.2G2 

 5.687 



Therms. 

 0.357 

 2. 377 



Do 





2.095 



3. 575 



2.020 





I _ 



1 Bureau of Animal Industry, Bulletin 128, pp. 177 and 184. 



a Computed to 12 hours' standing. 



a Corrected to the same live weight as in Period III. 



