72 



Feeds and Feeding. 



it grows and takes more exercise, the processes which lead to the 

 breaking down of the nutrients and their waste from the body be- 

 come more pronounced, and the proportion of food which forms 

 body substances steadily diminishes. 



Gain in body substances by well-nourished young animals is rel- 

 atively much greater than by mature animals even when fattening. 

 The unweaned calf may increase 2 to 3 Ibs. daily for each 100 Ibs. 

 of body weight, while a gain of 0.3 to 0.4 Ib. daily per 100 Ibs. of 

 body weight is large for the mature fattening ox. The more rapid 

 increase in weight of young animals is due to several causes their 

 flesh contains more water; their food is more digestible and con- 

 centrated; and they consume more food in proportion to live 

 weight. As growth continues, the total quantity of food eaten in- 

 creases, but the amount per 1000 Ibs. live weight diminishes. The 

 daily gain and the consequent returns from food consumed also 

 steadily decrease until maturity is reached, when there is no 

 further gain whatever unless from the laying on of fat. 



The following table by Armsby 1 shows the gain of protein, mostly 

 muscular tissues, by the growing ox at various ages: 



Storage of protein by the growing ox. 



The table shows that when 8 days old a calf stored daily in its 

 body tissues protein equal to 2.35 per ct. of the total protein then in 

 its body, or about 4 Ibs. daily per 1000 Ibs. of live weight. The 

 storage of protein, which practically measures the growth of muscu- 

 lar tissues in the body, steadily decreased with age and growth until 

 the 100-day-old calf stored 1.19 Ibs., or less than one-third as much 

 as the 8-day-old calf. When 28 months old and nearly mature, the 

 steer stored but 0.09 Ib. of protein daily per 1000 Ibs. of body 

 weight. It is thus shown that, as the animal matures, the quan- 

 tity of protein built up in the body steadily diminishes. 



1 U. S. Dept. Agr., Bur. Anim. Ind., Bui. 108. 



