46 PRINCIPLES OF FEEDING FARM ANIMALS 



needs of the body for maintenance purposes. The excess can then 

 be utilized for the manufacture of animal products, and for the 

 production of mechanical work. 



More than one of these purposes are frequently attained ; e.g., 

 the dual-purpose breeds of cattle are kept with a view both to milk 

 production and to raising beef calves or steers. Sheep produce mut- 

 ton and wool; with some breeds wool production is the important 

 object in view ; with others, the production of both wool and mut- 

 ton enter into the industry as factors, with emphasis laid on the 

 production of mutton; A similar dual purpose is attained in the 

 case of fowls kept for both egg and meat production. In the case 

 of the draft animals, the object in view is mechanical work in some 

 form or other, whether it be to pull a wagon or a plow, or to carry 

 a rider. In South-European countries, dairy cows also do light 

 farm work, so that these animals may be said to serve a triple pur- 

 pose, furnishing at different times of their lives milk, work and beef. 



The various animal products may be divided into two heads (a) 

 nitrogenous products, viz., meat and other materials, like wool, 

 milk and eggs, in which a large proportion of the solid matter con- 

 sists of protein substances, and (b) fatty tissue, composed mainly 

 of fat and water, with some nitrogenous substances. The produc- 

 tion of fatty tissue is not primarily the object sought by the feeder, 

 but accompanies or follows meat production, the fat being formed 

 between the muscle fibers and around the internal organs and 

 the carcass. 



Functions of Protein. — Evidently only nitrogenous feed com- 

 ponents can supply the necessary material for the formation of body 

 protein, since no other substances contain the " building stones " 

 (amino acids), from which the protein molecule is built up. Since 

 the exercise of vital functions is always accompanied by a con- 

 tinuous breaking down of body protein, the feed must contain 

 sufficient protein for new-building of body tissue in addition to that 

 required for body maintenance. The formation of muscles (flesh) 

 takes place most readily in the body of the young animal and grad- 

 ually decreases toward maturity. A mature animal cannot ma- 

 terially increase its muscles, and if it is fed a large supply of high- 

 protein feeds, the excess of protein will be used in the same way 

 as non-nitrogenous nutrients', for the production of heat, work, or 

 chemical energy in the form of body fat. In the case of mature 

 animals, heavy protein feeding also gives rise to an increased pro- 

 duction of heat in the body, and causes respiration to become more 

 rapid. In young animals, on the other hand, the feeding of large 

 amounts of protein will result in the largest development of nitrog- 

 enous body tissues and fluids of which the animal is capable. 



