MEAT PRODUCTION 433 



able energy of the rations consumed and the approximate 

 maintenance requirements per day and head were : 



TABLE m. DIMINISHING AVAILABILITY OF FEED 



In Period I, 48.5 per cent of the metabolizable energy of the 

 ration was available for growth as compared with only 27 per 

 cent in Period X. 



In brief, then, the undisputed superiority of the young animal 

 as regards -the amount of feed required to produce a unit of 

 increase may be reasonably ascribed : - 



First, to the fact that his feed is often of a more concentrated 

 nature, containing a greater proportion of digestible matter and 

 perhaps causing a smaller expenditure of energy in connection 

 with its digestion and assimilation. 



Second, to the fact that the gain of live weight in the young 

 animal contains a less percentage of dry matter and especially 

 of fat and therefore represents the storage of less energy than 

 the same increase in the older animal. 



Third, that the total feed consumption of the animal, espe- 

 cially upon the more bulky feeds generally used for simple 

 growth, may not increase as rapidly as the maintenance re- 

 quirement, so that an increasing proportion of the feed is 

 required simply for maintenance and is unavailable to produce 

 increase. 



511. Production of lean meat. The difference in the nature 

 of the gain made at different ages which, as has just been shown, 

 is a material factor in determining the cost of gain in live weight, 

 is of even greater importance in another aspect of the matter. 



As shown in Chapter XI (460-463), the capacity for growth 

 in the stricter sense, i.e., for increase of protein tissue, is especially 

 characteristic of the young animal and decreases rapidly as he 

 grows older, while it does not appear that it can be materially 



2 F 



