MINERALS REMOVED BY ANIMALS 19 



With regard to milk sold off the farm, each cow 

 giving on an average 600 gallons per year will take an 

 amount of minerals from the food, and indirectly from 

 the soil, equal to 210 Ibs. pure nitrate of soda, 87 Ibs. 

 superphosphate of lime (30 per cent, soluble phosphate), 

 19 Ibs. pure sulphate of potash, and 14 Ibs. ground lime. 

 For a thousand-gallon cow the respective amounts of 

 minerals required would be supplied by 350 Ibs. nitrate 

 of soda, 143 Ibs. superphosphate of lime, 32 Ibs. sulphate 

 of potash, and 22 Ibs. ground lime. The annual drain 

 to the farm by dairy cows is therefore considerable. 



When purchased foods are given to farm animals, the 

 loss of minerals to the farm is diminished theoretically 

 by the amount contained in the purchased foods. 



VI. BODY REQUIREMENTS PROM POOD. 



There is a continual waste going on in the animal 

 body, and it will be convenient to deal with these 

 losses or requirements separately. 



Body Temperature. The normal temperature of 

 farm animals is approximately 100 F. In this country 

 the air temperature seldom comes anywhere near body 

 temperature, and is often far below, with the result that 

 the body is constantly losing heat, chiefly from the 

 lungs and the external surface of the body. Experi- 

 ments have shown that the loss bears a much closer 

 relation to the exposed surface of the body than to the 

 weight of the animal. 



The rate of loss varies directly with the difference 

 between the air temperature and body temperature, i.e., 

 the greater this difference is, the more rapidly will heat 

 be lost from the body. The rate of loss may also be 

 increased by work, inasmuch as some of the energy in 

 the body is transformed into heat by increased oxida- 



