308 POULTRY PRODUCTION 



same class are manufactured, as is also the case with ash 

 and water, the organic nutrients (protein, carbohydrates, and 

 fats) of the feed perform other services to the body. The 

 carl)ohydrates and fats are largely responsible for furnishing 

 the energy with which both voluntary and involuntary work 

 is pcrfonned. The waste tissue is repaired with protein and 

 the repriiductivc dements are largely protein. 



A summary of the uses of the nutrients is given below, 

 with the less important class placed in parentheses:' 



Service Rendered. Classes. 



Furnishing energy. Cailiuliydrate and fat (protein). 



Repairing waste tissnr;. Protein. 



Furnishing material for iirijwlli. Protein and ash. 



Reproduction. Protein (carbohydrate and fat). 



Fattening. Carbohydrate and fat (protein). 



THE VITAMINS. 



In the past the feed has lieen regarded chiefly as the source 

 of the material necessary for the constructive processes going 

 on in the body and of the energy required to support its 

 A'arious acti\'ities. This aspect i)f the matter has been promi- 

 nent in the ])receding paragraphs. 



liccent investigations, however, are bringing into promi- 

 nence another class of influences exerted by the feed upon the 

 organism. The study of the \itamins is rendering it increas- 

 ingly evident that quite aside from its value as a supply of 

 structural material and of energy, the nature of the feed n^ay 

 ]ir<>foundly influence the results of feeding. 



It is clear that the vitamins influence the nutritive value of 

 a feeding stuff in an essentially dift'erent way than does the 

 (|uantity of ash, ])rotein and energy which it supplies. The 

 latter limits the anidUiit (if pnuluction which the feeding stuff 

 can su]i]>ort; tlie former may determine how much of the 

 nutrients supplied ntay actually be used. A mixture of jiure 

 nutr'cnts nia>" be ])re])ared upon which young animals fail 

 to grow, V. Iiile the addition to such a mixture of minute 



' Atter Jalfa, California Bulletin No. 164. 



