446 NUTRITION OF FARM ANIMALS 



increase of the total protein and still less of meat proper can be 

 secured. Evidently the question of the necessary protein supply 

 in the rations of meat-producing animals is of special impor- 

 tance during the early stages of growth. 



524. Minimum protein supply for growth. The meat-pro- 

 ducing animal, then, in order to utilize fully his capacity for 

 growth must be supplied in his feed at each stage of that growth, 

 in addition to his maintenance requirement, with at least as 

 much digestible protein as he is capable of storing up in his 

 growth. Whether any greater quantity than this is necessary 

 or advantageous is, as has been shown (491), still to some de- 

 gree an unsettled question. Some experiments, especially with 

 cattle and sheep, indicate that any considerable surplus is un- 

 necessary for normal growth, while, on the other hand, feeding 

 experiments with pigs and to some extent with ruminants indi- 

 cate that amounts considerably in excess of those thus com- 

 puted assure at least greater gains of live weight. 



525. Protein requirements in fattening. While growth 

 and fattening may be regarded physiologically as distinct pro- 

 cesses, it is economically important in the practice of meat pro- 

 duction that they should go on more or less simultaneously. 

 The growth of even the very young animal is not simply a 

 production of protein tissue, but normally includes more or less 

 fat production, while in proportion as one has to deal with 

 early maturing animals it is desirable to begin the fattening 

 proper at a comparatively early stage of growth (512). 



There appears to be no reason for regarding the actual fatten- 

 ing process as being essentially different in the growing and 

 in the mature animal. It has been shown, however (453, 456) 

 that in the latter case no material excess of protein over that 

 required for maintenance is necessary. So far as the mere 

 supply of building materials is concerned, therefore, there seems 

 no reason to suppose that the actual protein requirement for 

 combined growth and fattening is any greater than that for 

 normal growth without fattening. The conclusions regarding 

 the protein requirements for growth recorded in Chapter XI 

 (482), therefore, may be regarded as applicable also to young 

 animals that are being fattened, especially since they were de- 

 rived in part from results on immature fattening animals, and 

 from this point of view the increased feed supply required for 



