290 



Nature-Study Agriculture 



Substances 

 of which 

 the animal 

 body is 

 composed 



The body 

 of an 

 animal 

 compared 

 with an 

 engine 



Mineral 

 matter in 

 feeds 



young needs very much more than these quantities. 

 Twice a day is often enough to feed rabbits ; but hay 

 should -be kept before them in a rack at all times. Grain 

 can be given in the morning and green feed at night. 



Principles of feeding. We may get some idea of the 

 kinds of feed that stock requires if we consider of what 

 materials the body of an animal is made up. The bones 

 contain large amounts of mineral matter, such as lime 

 and phosphorus. The muscle the lean meat is 

 made of a nitrogenous substance called " protein." 

 (Exp. i.) There is. some fat in all animals; and every 

 part of the body, but especially the blood, contains 

 quantities of water. Evidently the food must contain 

 something that will make bone, muscle, fat, and 

 blood. 



It will help us in our study of the food needs of ani- 

 mals if we think of the* body of an animal as being in a 

 way like an engine, since the food that is digested, like 

 fuel burned under a boiler, produces heat and energy. 

 A hard-working animal requires more food, just as an 

 engine drawing a heavier load than usual requires more 

 fuel ; and in winter more food is needed than in summer, 

 in order to keep up the body temperature. It has been 

 found that all foods give as much heat when digested 

 as when burned though more slowly. A food that 

 will give a great deal of heat is a food that will give a 

 great deal of energy to be used in doing work. 



The ordinary feed of animals furnishes most of the 

 mineral matter needed. Oats, for example, is a good 

 bone-making feed, containing three pounds of mineral 

 matter in each hundred pounds. Corn contains half 



