MAINTAINING FARM ANIMALS 53 



ing may produce 30 per ct. more heat than when lying down. 

 Exposure to cold winds, especially with animals having scanty coats, 

 increases the need for body fuel. Animals with coats wet by rain or 

 snow lose still more heat from their bodies, for the cold water must be 

 warmed and evaporated by heat produced thru the burning of food in 

 the body. With heavily-fed fattening animals this may not cause 

 any waste of food nutrients, for much more heat is being produced in 

 the mastication, digestion, and assimilation Qf their heavy rations 

 than is ordinarily needed to warm the body. On the other hand, 

 animals being carried thru the winter on scanty rations have no such 

 excess of heat, and hence much feed may often be saved by protecting 

 them from cold winds and storms. 



II. Requirements for Protein 



Protein required for maintenance. — The demands of the body for 

 fuel and energy can be met thru feeding carbohydrates and fat. 

 However, an abundant supply of these nutrients alone will not pre- 

 vent starvation, for there must also be a supply of protein to replace 

 that lost each day from the body ; that is, to repair the protein tissues. 

 In view of the high cost and relative scarcity of protein in feeding 

 stuffs, it is important to know the smallest amount of this nutrient 

 which will maintain animals in good health. When plenty of carbo- 

 hydrates and fat were supplied to serve as body fuel, animals have 

 been maintained for long periods on surprisingly small amounts of 

 protein. For example, at the Pennsylvania Station * Armsby main- 

 tained steers on only 0.4 to 0.6 lb. of digestible protein daily per 

 1,000 lbs. live weight without harm. It is not well, however, to 

 supply only the theoretical minimum of protein to animals for long 

 periods. Some allowance must be made for the difference in com- 

 position of feeding stuffs and the varying abilities of animals to 

 digest the same feeds. We should further remember that the various 

 proteins differ in composition and that some are so unbalanced as to 

 have but low value for repairing body tissues. In numerous experi- 

 ments animals have never been successfully maintained on gelatin, a 

 protein which lacks two amino acids and contains only small amounts 

 of others. Besides supplying protein to replace the daily waste from 

 the tissues and organs of the body, there should be provision for the 

 growth of the hair, hoofs, and wool— all of a protein nature. In gen- 

 eral, protein is a cell stimulant and a supply somewhat above the 

 minimum promotes the health of the animal. 



The wisdom of not limiting the protein supply to the theoretical 

 minimum for long periods has been shown by the experience of 



i Principles of Animal Nutrition, 1903, p. 142. 



