Nutrition of the Animal Body 239 



335. Economy of Balanced Rations. When the pro- 

 teids and heat -producing substances are supplied in 

 the ratio approximately in which they are consumed, 

 the ratio is said to be "balanced." There may be wide 

 limits in the nutritive ratio without imparing the general 

 health of the animals, but there may be a great differ- 

 ence in the cost of properly nourishing the animal. The 

 feeds rich in proteids are very expensive, and it is desired 

 that they be used only in the formation of nitrogenous 

 products, and never to supply energy. The cheaper 

 starchy foods should be used in sufficient quantity 

 to supply heat and muscular energy. Thus, we see 

 that by knowing something of the composition and 

 digestibility of the common feeds, we may combine 

 them in such proportions that the animal may be prop- 

 erly nourished at small cost. 



336. Kinds of Rations. Rations are classed accord- 

 ing to their effect on the animal, as regards bodily weight 

 or function. The most usual designations are: 



(a) Deficient ration is one in which the animal 

 loses weight. 



(b) Maintenance ration is one which allows just 

 enough to keep the animal in good health without loss 

 or gain in bodily weight. This is usually about three- 

 fourths to one pound of nutrients to the hundred pounds 

 of live weight. 



(c) Growing ration is one allowing of a regular 

 gain in weight. The amount af feed which a young 

 animal may profitably consume varies widely, usually 

 from 2 to 4 per cent of live weight. 



(d) Work ration is one that will sustain an animal 

 at work without loss of weight or vigor. 



(e) Dairy ration is one that supplies the materials 



