GROWTH 403 



not only supply net energy equal to that contained in the growth 

 made, as indicated by the foregoing table, but in addition 

 sufficient net energy for maintenance, the sum of the two being 

 the total net energy required by the animal. Computing 

 from Table 94 and from the estimated live weight at different 

 ages * the energy storage per head and adding the maintenance 

 requirement computed in proportion to the two-thirds power 

 of the live weight (347) gives the total energy requirements 

 shown by Table IV b of the Appendix. 



Protein requirements 



484. Minimum requirement. As with the energy of the 

 feed, the protein supply of the growing animal is essentially a 

 limiting factor. A deficient supply or one lacking certain 

 essential " building stones " (465), may check growth tem- 

 porarily or permanently through simple lack of material, but 

 it does not appear that a surplus of protein can materially 

 stimulate the rate of growth. 



Granting the approximate accuracy of the estimates of the 

 actual gain of protein in normal growth made on previous 

 pages (463, 479), the quantity of digestible feed protein re- 

 quired in the ration of the growing animal at any particular 

 age will depend upon what proportion of the latter can be con- 

 verted into body protein and stored up, i.e., upon the percentage 

 utilization of the feed protein (470). As was shown in the 

 preceding section, however, this is very imperfectly known. 

 If, on the basis of Fingerling's and Just's results (471), it be 

 assumed that the utilization may approach 100 per cent, then 

 the amounts estimated in Table 91 (479), with the addition of 

 about 0.5 per 1000 for maintenance, would be the least amounts 

 of digestible protein which must be supplied to support the 

 normal increase of protein tissue. 



485. Results in practice. As a matter of fact, however, 

 experience seems to show that a more liberal supply of feed 

 protein than is indicated by these estimates is at least advan- 

 tageous if not necessary in the actual rearing of animals. While 

 there are few investigations on record directed specifically to 

 the determination of the minimum protein requirements of 



1 In direct proportion to the live weight. 



