CHAPTER VI 



ENERGY IN FEEDINGSTUFFS AND ITS USES IN 

 THE ANIMAL BODY 



Energy is defined by the physicist as the capacity of per- 

 forming work. Inasmuch as the muscular tissues of farm 

 animals are always doing a certain amount of work, it is of 

 interest to study the ways in which animals utilize energy 

 and to study the values of the different nutrients and the 

 different feedingstuffs as sources of energj\ 



There are two kinds of energy, kinetic and potential 

 Kinetic energy is energy due to motion ; e.g. a moving train 

 has energy due to its motion ; heat is a form of energy duo 

 to the motion of the heat waves. In other words, kinetic is 

 active energy. Potential energy is energy due to position 

 or composition ; e.g. a coiled watch spring has energy due 

 to its position ; starch has energy due to its composi- 

 tion. Potential energy is stored energy. These two forms 

 of energy are interchangeable from one to the other. 

 Thus the plant by means of its chlorophyll can take the 

 kinetic energy or heat of the sun's rays and change it to 

 the potential form, storing it in the form of proteins, car- 

 bohydrates, and fats. This potential energy may be changed 

 back to kinetic form by burning the plant and liberating the 

 stored energy in the kinetic form as heat. In similar manner, 

 the animal can take the potential energy of its feed and 



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