20 THE STOCKFEEDER'S COMPANION 



tion of the nutrients in the body. The heat escapes 

 both through the lungs and the pores of the skin. 



Mechanical Work or Energy. The animal body 

 has many functions to perform, both internal and 

 external, in order to keep up its vitality. Internally, 

 the process of respiration must go on, and this throws a 

 lot of work on the diaphragm and other muscles. The 

 heart has to be continually pumping the blood round 

 the body. As the food passes along the alimentary track 

 it must be masticated, digested, and largely expelled 

 from the system ; while externally the body requires to 

 be held in position, and, during walking or running has 

 to be carried or forced through space, which involves a 

 considerable amount of strain on the muscles. If, how- 

 ever, the animal is loaded, then the strain on the 

 muscles is increased, and the animal respires more 

 freely. All these things are a drain on the energy 

 which is stored in the system. 



Maintenance. Ordinary wear-and-tear is constantly 

 going on in the body, due to the strain thrown on the 

 system in meeting the various demands, such as the 

 production of heat and the performance of internal 

 work. The body tissues are continually being used up, 

 and in order to keep the animal in the same condition 

 (*>., neither increasing nor decreasing in weight), it is 

 necessary to give it a sufficient amount of nutrient 

 material to maintain its body temperature, to supply 

 energy, and repair the waste of tissue. 



Production. This refers more to the growth in 

 size of animals, production of flesh (beef, mutton, or 

 bacon), as well as offspring and milk. It really infers 

 that something extra is required over ordinary mainten- 

 ance. In fattening animals, it is only the food consumed 

 in excess of the requirements for maintenance (heat, 



