444 PRINCIPLES OF AGRICULTURAL CHEMISTRY 



often been found profitable to warm the drinking water, especially 

 for hogs. 



If the external temperature is too high, the animal may have 

 trouble in disposing of the heat from the excess of thermal 

 energy, and will then eat less of the ration. For this reason 

 fattening in summer may be difficult ; in some parts of the South, 

 animals fatten better when fed out of doors where the perspira- 

 tion may evaporate freely, than when confined. It is also often 

 advisable to feed light, rather than heavy fattening rations during 

 warm weather. 



Condition of Animal. The fatter the animal, the more food 

 required for maintenance, and the less the proportion of it avail- 

 able for fattening. Thus the cost of the production of fat in- 

 creases with the duration of the fattening process. 



Age of Animal. South Dakota 1 experiments show the follow- 

 ing relation between feed consumed and gain in weight, for cattle 

 of different ages. 



Excess Over Maintenance Requirements. Only the excess of 

 food over the maintenance requirement can be used for produc- 

 tion. The larger the excess, within the limit of the ability of the 

 animal to use it, the more economically the food is used. For 

 example, if a steer weighing 1,000 pounds that requires 1.5 pounds 

 productive value for maintenance, is fed 2.0 pounds, then only 

 0.5 pounds, or one-fourth of the ration is used for production of 

 fat. But this animal should be able to use 3.0 pounds productive 

 value, and in such case 1.5 pounds, or one-half of the value of the 

 food is used for fat. The fat produced by the first ration will 

 require twice as much productive value as that formed by the 

 1 Bulletin No. 125. 



