430 NUTRITION OF FARM ANIMALS 



1 1 oo pounds of increase. The difference as regards feed cost 

 comes in the expenditure for maintenance, since each pound 

 of gain, as well as the original 100 pounds, must be maintained 

 from the time it is laid on until maturity. The animal, then, 

 which has the higher rate of growth and which matures in 

 two years costs the owner a notably less expenditure for feed 

 than the one maturing in three years, to say nothing of the 

 saving in cost of attendance and in interest on the investment. 



Age 



506. Influence on cost of production. It is an undisputed 

 fact that gain is made more rapidly and more cheaply by the 

 younger as compared with the older animal. This is true both 

 in growth proper and in the commercial fattening of partly 

 mature animals. 1 



On the other hand, it was shown in Chapter XI (472-476) that 

 there is no experimental evidence that the capacity of the young 

 animal for making a more rapid gain is due to any greater 

 physiological economy in the conversion of surplus digestible 

 material into tissue, while it has also been established (720) 

 that the digestive power of the young animal is not materially 

 different from that of the mature animal. As regards protein, 

 the indications are that the loss of nitrogenous material in the 

 actual conversion of feed protein into body protein is not or- 

 dinarily great and is no greater in the old than in the young 

 animal, while as regards energy it was shown that the proba- 

 bilities are in favor of the view that its utilization is less rather 

 than greater in the younger than in the older animal. 



507. Causes of greater economy. More or less confusion of 

 thought has resulted from this apparent conflict of evidence, 

 while feeding experiments like those cited by Henry and Morri- 

 son have been made the basis of unwarranted inferences as to 

 the greater digestive and assimilative powers of young animals. 

 This confusion has arisen to a large degree through failure to 

 distinguish between physiological and commercial economy 

 and it is important to secure a clear conception of the elements 

 of the commercial superiority of the younger animal. 



1 Compare Henry and Morrison, Feeds and Feeding, i5th Ed., pp. 431-434, 512, 

 568-572. 



