FOOD AND FEEDING 681 



quirements,* we find that 0.45 lb. of digestible protein and food 

 of energy value of 5.6 therms are necessary. Multiplying the a.i- 

 ditional requirements for each pound of milk produced (as 

 above) by 25, we find that 1.35 lbs. of protein and 7.5 therms 

 are necessary for this milk yield— beside the maintenance re- 

 quirement. Adding the requirements for maintenance to those 

 for milk yield we get the total daily requirements for cows 

 weighing 850 lbs. and yielding 25 lbs. of milk as follows: 



Digestible protein. Energy value, 



xi, . ^ Lbs. Therms. 



h or maintenance ^'i ^i fi 



For 25 lbs. of milk 1:25 7:5 



1.70 13.10 



We shall now have to consult a table* showing the energy 

 value, proteid content, and dry matter in all ordinary fodders, 

 and combine them so that they shall possess in the daily ration 

 1.7 lbs. of digestible protein, energy value of 13.10 therms, 

 and dry matter equal to 20 to 30 lbs. 



The particular food stuffs must be selected so that they 

 shall be the cheapest in the locality in which the feeding is done. 

 The mechanism of the animal body is always "running," 

 ■ and an animal at rest is like a motor car at a stand-still with the 

 engine moving. Therefore no more protein is required by a 

 horse at lightwork than at rest, for repair of the machine. 

 More fuel for running* the machine is, however, needed. The 

 requirements for working horses are : For light work, digestible 

 protein, 1.0 lb. ; therms, 9.8; For moderate work, digestible 

 protein, 1.4 lb. ; therms, 12.40. For heavy work, digestible pro- 

 tein, 2.0 lbs.; therms, 16.00. 



Horses doing hard work, growing and pregnant animals, 

 and all animals supplying nitrogenous products, as wool and 

 milk, demand more nitrogen- in their food. The proteids, as 

 we have seen, constitute a large proportion of the solids and 

 fluids of the body. The protein absorbed into the blood, is 

 utilized in two ways. One part is Energy-forming, the circula- 

 tory protein of Voit. The other part is Tissue-building, or the 

 Organic Protein of Voit. 



That part which is devoted to energy-producing is not 

 transformed into tissue but is split up (katabolized) by the 



*Armsby, Bull.> 346, U. S. Dep't. Agric. 



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