48 



PRINCIPLES OF FEEDING FARM ANIMALS 



By means of the respiration calorimeter the amount of heat 

 produced by the oxidation of the digested nutrients in the animal 

 body is determined. The distribution of the losses of energy to 

 the animal in the dung, urine, and marsh gas, as well as the net 

 energy contained in the different feeding stuffs, is also shown by 

 the results obtained in trials with this apparatus. 



The following table shows the distribution in therm units in 

 the case of three common feeds, as determined by Armsby : 



Energy in Different Feeding Stuffs per 100 Pounds, in Therms 



We note that, while clover hay and corn meal contain nearly 

 the same amount of total energy, only 43 per cent of this is avail- 

 able to animals in the case of clover hay, against 78 per cent in the 

 case of corn meal. 



Available Energy. These figures and others similarly obtained 

 do not, however, tell the whole story. Clover hay and other rough 

 feeds are bulky and call for a large amount of work in mastication 

 and moving it through the alimentary canal, and also necessitate 

 the secretion of larger amounts of digestive fluids than do corn 

 meal and other concentrates. The energy required for these pur- 

 poses is likewise lost to the animal, so far as production or work is 

 concerned, and can be provided only through that supplied in the 

 feed. The balance, which is known as net available energy or net 

 energy, represents that available to animals for maintaining the 

 vital functions or for productive purposes. 



The results obtained in respiration experiments with steers show 

 that a larger percentage of the energy value of concentrated feeds 

 is available for maintenance or for production than in the case of the 

 rough feeds. In the poorest of these, as wheat straw, only small 



