MEAT PRODUCTION 429 



cally by increase of protein tissue or practically by gain in 

 weight. 



In whichever sense the term maturity is used, however, the 

 matter reduces itself to the question of rate of growth. The 

 greater the initial impulse to growth, the sooner, other things be- 

 ing equal, will the animal complete his growth, while if the rate 

 of growth can be made sufficiently rapid the desired accumula- 

 tion of meat, and consequent weight, may be reached before 

 physiological maturity. In other words, the rate of growth may 

 be looked upon as expressing the capacity of the machine, since, 

 as was stated in Chapter XI, it is substantially determined 

 by biological factors and is apparently little affected by the feed 

 supply, provided only that the latter is adequate. 



505. Economic significance. There seems no reason to 

 suppose that there is any material difference as regards physio- 

 logical economy between rapid growth and slow growth ; that 

 is, there is no reason to suppose that the storing up of certain 

 amounts of protein and energy in the body of an animal in one 

 month requires any greater or any less total feed supply, in 

 addition to the maintenance requirement, than the storing up of 

 the same amounts in the two months' time, except as heavy 

 feeding may diminish the percentage digestibility of the ration 

 (722). In other words, it may be assumed that if a gain of one 

 pound in live weight contains 2500 Calories of energy, the ra- 

 tion must supply that amount of net energy above the main- 

 tenance requirement within the time required to make the 

 gain, whether that time be one day or three. 



From the economic point of view, however, there is a very 

 important difference which explains the stress laid upon early 

 maturity in meat-producing animals. It is plain that, other 

 things being equal, the animal which inherits the greater initial 

 impulse to growth, and in which that impulse dies out the more 

 slowly, will reach either physiological maturity or a given size 

 and weight sooner than the one in which that impulse is less. 

 It makes a very material difference, however, to the producer 

 of beef cattle, for example, whether a calf weighing 100 pounds 

 at birth has the capacity to reach a weigh of 1200 pounds at 

 two years old, or whether he requires three years to do it. This 

 is not, however, because there is any material difference in the 

 amount of feed which the animal requires to manufacture the 



