80 A STUDY OF FARM ANIMALS 



raise the temperature of 1 pound of water 4 F. The word 

 therm is now being adopted as more convenient for use in 

 referring to stock feeding. A therm equals 1,000 calories. 

 If we raise 1,000 pounds of water 4 F, that measures a therm. 

 While food is being digested in the body, heat is produced 

 by the process. Some foods contain more heat than others. 

 The difference will depend largely on the amount of fat con- 

 tained. Scientific men consider that the heat values of pro- 

 tein and carbohydrates are about alike, but that the heat 

 value of fat is 2J^ times as great as either of these. This 

 fact partly explains why the Eskimos in the cold North eat so 

 much food that is nearly all fat, as the blubber of the whale. 

 Corn contains more fat than any of our other common 

 grains, which fact accounts in part for its use as a winter 

 feed for horses, and also is a reason why it should not be fed 

 heavily to stock in su'iimer in the warm season. 



Food has an energy value. When a substance is burned, 

 the resulting energy furnishes power to do work. So it is 

 understood that what we call a therm represents the energy 

 or work necessary to raise 1,530 tons to a height of one 

 foot. Part of the energy of the food, to be sure, is lost in 

 the process of digestion, partly because not all the food is 

 digested. But much of it is saved, and this is used to keep 

 the engine of the body going. The horse that pulls the plow 

 or hauls a load of hay gets his power from the stored-up 

 energy in the food, which is set free in the body during oxida- 

 tion in the process of digestion. 



The heat and energy value of food has been worked out 

 by scientific men, by means of a calorimeter. This is a very 

 strong, round, hollow steel tube. A sample of a food is 

 placed in this and burned, and the amount of heat given 

 off is measured. Another instrument, called the respiration 

 calorimeter, also is used, in which a live animal is placed. 

 With this the investigator can study the value of foods, and 

 can make a complete record of just what becomes of all 



