THE SELECTION OF FOODS 45 



the opposite will follow if these nutrients are insufficient 

 in supply. It would be easily possible to feed foods so 

 out of balance as to entirely defeat the objects for which 

 animals are grown. An exclusive corn diet for instance, 

 fed to swine grown and maintained for breeding uses, 

 would in time, reduce size, weaken bone and destroy 

 breeding properties, so highly carbonaceous is it. 



Tivo factors add much to the difficulty found in feed- 

 ing foods in equilibrium or balance. One of these is the 

 variations in the needs of the animals to which the foods 

 are fed, and the other is the variations in foods at differ- 

 ent periods of growth. Take for instance the horse 

 grown for work. When a colt, much protein is needed 

 in the food to make muscle and much ash to make bone. 

 When the animal is grown and set to work, a much 

 larger proportion of carbohydrates are needed to sustain 

 energy and to prevent excessive waste of tissue. These 

 variations must be taken into account by the successful 

 feeder and he must strive to govern his work accord- 

 ingly. 



Variations in the foods are to some extent caused by 

 variations in climate and soil. These are not usually 

 greatly significant in degree. But those variations are 

 greatly significant that relate to the constituents of 

 plants at different stages of development. Take for 

 instance the corn plant. In the early stages of its 

 growth, it is succulent, and not specially rich in carbo- 

 hydrates. These increase with increasing maturity in 

 the plant. Subsequently to harvesting, the food nutrients 

 are decreased in the fodder by exposure and it loses in 

 palatability. Hence the value of corn as a food plant 

 varies continually at every stage of its growth and 

 utilization. 



Some few foods are balanced in themselves. Grass is 

 one of these. This at least is true of some kinds of 

 grass. Because it is so, additional food is not usually 

 given to animals abundantly supplied with grass. 



