PRINCIPLES OF STOCK FEEDING 



53 



This is true even when the foods fed 

 contain no nitrogen whatever. Even 

 when animals receive no food at all and 

 are starving, nitrogen is found in the 

 urine. In these cases the only possible 

 source of the nitrogen found in the urine 

 is the protein previously stored in the 

 body. The nitrogen in the urine repre- 

 sents the protein that was used in the 

 body in carrying on its vital functions. 



In the living animal of whatever age, 

 a certain amount of protein or flesh is 

 constantly destroyed in the life processes 

 and is removed from the body through 

 the urine, while new tissue is constantly 

 built up out of the protein obtained 

 from the digested food to replace that 

 broken down and destroyed. Protein is 

 used constantly in the body of all ani- 

 mals. This is true whether the animals 

 are young or old and whether they are 

 at work or at rest. If the protein in the 

 foods supplied is more than sufficient to 

 maintain the vital activities of the ani- 

 mal, the excess, within limits, may be 

 stored as flesh. 



Forms of protein— On the basis of 

 careful experiments, it is believed that 

 protein exists in the body in two forms. 

 In one form it is unstable and rapidly 

 destroyed. In the other form it is com- 

 paratively stable and only slowly de- 

 stroyed. It Las been suggested that in 

 the first instance the protein destroyed 

 may be that which has been carried to 

 the cells of the body, but which has not 

 yet become organized, while in the 

 latter case the protein has become organ- 

 ized into the tissues of the different 

 organs. 



Organized protein or flesh constitutes 

 by far the greater part of the protein of 

 the body, and in mature animals re- 

 mains nearly constant, the amount de- 

 stroyed each day being practically less 

 than one per cent. The quantity of pro- 

 tein not organized into flesh, or "circu- 

 latory protein" as it has been called, on 

 the other hand may vary greatly. In 

 starving animals the circulatory protein 

 may be practically nothing, while in an- 

 imals well fed on foods containing a 

 large amount of digestible protein it 

 may equal as much as 5 per cent of the 

 organized protein. But while less than 

 1 per cent of the organized protein is 

 destroyed each day in the vital processes, 

 70 to 80 per cent of the circulatory pro- 

 tein may be destroyed. 



It is thus seen that the bodily func- 

 tions are maintained largely at the ex- 



pense of the circulatory protein which 

 varies in amount from day to day with 

 the amount of digestible protein in the 

 food. 



A certain amount of protein i n the 

 food is essential to life. If the protein 

 supply in the food is increased above 

 this amount, a temporary gain in flesh 

 occurs and a rapid increase in the cir- 

 culatory protein. With every increase, 

 however, in the amount of protein sup- 

 plied in the food there is a correspond- 

 ing proportionate increase in the amount 

 of protein consumed in the body and 

 excreted in the urine. No matter, there- 

 fore, how great the amount of protein 

 supplied in the food any excess beyond 

 the normal amount required to keep the 

 animal in good condition will not be 

 formed into flesh, but will be consumed 

 in the body and excreted in the urine. 



On this point Armsby states that the 

 "Animal body puts itself very promptly 

 into equilibrium with its nitrogen sup- 



Fig. 34 — beet pulp silos: A, open 

 silo; B, trench silo 



ply, and no considerable or long contin- 

 ued gain .of proteid tissue can be pro- 

 duced in the mature animal by even the 

 most liberal supply of proteid food." 

 This means that in fattening mature 

 animals there is practically no increase 

 in lean meat. The gain is largely due 

 to deposits of fat which contains no ni- 

 trogen. 



Other constituents — Thus far we have 

 spoken only of the protein constituent 

 of the ration in flesh formation. Pro- 

 tein, however, is seldom fed alone. It is 

 usually combined in feeding stuffs with 

 either fats or carbohydrates and usually 

 with both. Especially is this true with 

 all vegetable feeding stuffs like the hays 

 and grains. What effect do carbohy- 

 drates and fats have on flesh formation 

 when they are fed with protein? 



Less Protein Required — Experiments 

 have shown that when either carbohy- 

 drates or fats are fed in the ration with 



