364 NUTRITION OF FARM ANIMALS 



of its tendency to stimulate the general metabolism of the body 

 (365). 



454. Protein in increase. As appeared in i (444), how- 

 ever, the actual increase in mature fattening animals has been 

 found to contain a relatively small and rather variable propor- 

 tion of protein, due in part to the growth of epidermal tissue, 

 in part to an increase in the number of fat cells, and in part 

 to an actual storage of protein and nitrogenous extractives 

 in the muscular tissue (and in the internal organs?). It is to 

 be remarked, however, that in most or all instances the rations 

 consumed contained more protein than was necessary for main- 

 tenance, with, of course, an abundant supply of non-nitrog- 

 enous material, so that the conditions were favorable for such 

 a storage of protein as that just mentioned. So far as the writer 

 is aware, it has not yet been shown that the mature fattening 

 animal actually requires any surplus of protein over the amount 

 necessary for maintenance, although it can apparently utilize an 

 excess, at least to some extent, to increase the stock of protein 

 in its body. 



At most, the requirement of the fattening animal as meas- 

 ured by the observed storage of protein is relatively small, one 

 pound of increase in live weight containing in round numbers 

 from 0.02 Ib. to 0.08 Ib. of protein. 



455. Utilization of feed protein. Assuming the observed 

 gain of protein by the fattening animal to represent a real re- 

 quirement, it is evident that a sufficient fattening ration must 

 supply, in addition to the protein necessary for maintenance, 

 an additional amount sufficient, after undergoing the various 

 processes of digestion and metabolism, to yield the amount of 

 body protein contained in the increase of body weight. As 

 will appear more particularly in considering the subject of 

 growth (470, 471), little is known regarding the amount of feed 

 protein required to yield a unit of body protein. Doubtless 

 this will differ as between different individual proteins, depend- 

 ing, for one thing, upon the proportions of the different amino 

 acids which they contain, but adequate quantitative data are 

 as yet unavailable. 



456. Protein in fattening rations. In the absence of definite 

 knowledge regarding the availability of the protein of the feed, 

 the question of the amount of this nutrient which should be 



