BREEDS OF BEEF CATTLE 



299 



increase is not proportional to the weight of the animal, but approx- 

 imately to the amount of surface which it exposes, so that the large 

 animal requires less food in proportion to its weight to maintain it 

 than does the small one. 



The following tables show the amounts of protein and of energy 

 required per head for the maintenance of cattle, sheep, and horses of 

 different weights. The figures given for sheep include a sufficient 

 allowance for the normal growth of wool. No very satisfactory 

 figures for swine are available. It should be understood that strict 

 accuracy is not claimed for these figures, although they are sub- 

 stantially correct. In particular there seems to be reason to believe 

 that the maintenance requirement of fattening animals increases 

 somewhat more rapidly than these tables indicate. 



Maintenance Requirements of Cattle and Horses, Per Day and Head. 



Maintenance requirements of sheep, per 

 day and head. 



Estimated energy value of 

 I pound of gain in 

 weight by growing cat- 

 tle and sheep. 



Requirements for Growth. While young animals gain in 

 weight faster than do older ones, a pound of increase in live weight 

 in the young animal contains much more water and less dry matter 

 than in the case of a more mature animal. Moreover, the dry mat- 

 ter in the case of the young animal contains relatively more protein 

 and less fat, as a rule, than in the older one, and fat contains much 

 more chemical energy than protein, the proportion being 1 to 1.67. 

 The consequence is that a gain of 1 pound in live weight represents 

 the storing up of much less energy in the young than in the mature 

 animal, and therefore requires a smaller supply of energy in the 

 food. 



