426 NUTRITION OF FARM ANIMALS 



a protein diet. It is evident, however, that the commercial 

 growing of meat may involve the production of considerably 

 more fat than protein and that, in so far as this fat is actually 

 consumed, meat is far from being the distinctively protein 

 food which it is ordinarily considered. Thus the so-called 

 " nutritive ratio " of the average side of beef, calculated in the 

 usual manner, is about i : 3.5. On the other hand, however, it 

 is equally true that the proteins of meat are the distinctive in- 

 gredients for the sake of which it is produced and eaten, while 

 the fat, although a valuable nutrient, is to a certain extent sub- 

 sidiary and accidental. 



502. Processes involved. Corresponding in a general 

 way to the two main constituents of commercial meat, viz., 

 muscular tissue and adipose tissue, two distinct physiological 

 processes are involved in meat production, viz., growth and 

 fattening. 



Growth. The animal at birth is usually regarded as 

 unfit to serve as human food. Moreover, even were this 

 not the case it would be in the highest degree uneconomic 

 to fail to utilize the marked assimilative powers of the 

 young animal for the production of body tissue (meat) 

 from feed. Consequently the production of meat involves 

 more or less growth in all cases. This may, for special reasons, 

 be concluded early, as in the production of lamb or veal, but as 

 a whole the world's commercial meat supply is derived from 

 animals at least approaching maturity. This growth of animals 

 from birth to approximate maturity consists essentially of an 

 increase in the protein tissues (457), the rate of which is es- 

 sentially determined by the nature and individuality of the 

 animal and can at most be but slightly stimulated by an in- 

 creased protein supply (403, 484). 



Fattening. Fattening, on the contrary, is a process which, 

 in a given animal at least, is largely under the control of the 

 feeder. Substantially it is dependent on the quantity of feed 

 consumed by the animal in excess of the requirements for 

 maintenance and growth, and there is lacking any definite proof 

 that the actual storage of energy in the form of gain for a given 

 amount of excess feed is seriously affected either by the age or 

 the individuality of the animal. Fattening, therefore, may 

 take place at any age, although of course the greater demand 



