GROWTH 



373 



In spite of irregularities and gaps in the table two general 

 facts are clearly shown; first, that the percentage of water in 

 the gain decreases and that of dry matter increases with ad- 

 vancing age of the animal, and second, that of the dry matter 

 gained, an increasing proportion is fat as the animal matures. 

 The latter fact becomes especially clear if the composition of 

 the dry matter of the ash-free gain be computed. 



The result of investigations by Waters, Mumford and Trow- 

 bridge as reported by Henry and Morrison l are quite in accord 

 with the teaching of Table 79, the percentage composition of 

 the first and the second 500 pounds gained by young fattening 

 steers being as follows : 



459. Energy content of gain. The amount of energy 

 stored in a unit of increase in live weight shows a fairly regular 

 and notable increase as the animal grows older, due to the 

 smaller percentage of water and the higher percentage of fat 

 which it contains. The rate of increase in the energy content 

 per unit in those cases in which no considerable fattening of the 

 animal was attempted seems to be fairly regular up to about 3.0 

 Therms per pound and the same thing is also true of most of the 

 results upon fattening animals up to about 3.5 Therms per 

 pound, although the actual energy content per unit at the same 

 age is naturally greater in the fattening animal and the limit is 

 therefore reached earlier in life. In both cases the limit seems to 

 correspond in a general way with the average energy content of 

 the gain made by mature fattening animals as estimated in 

 Chapter X (451), viz., about 3.25 Therms per pound. The data, 

 however, are few and further investigation is much to be desired. 



Relation of growth to age 



460. The rate of growth. If the successive weights or 

 dimensions of a growing animal be platted, there are obtained 

 1 Feeds and Feeding, isth Ed., p.84. 



