PROTEIN REQUIREMENTS OF CATTLE: MITCHELL 



21 



TABLE 7 

 Rates of Growth of Missouri Cattle at Diffeuient Weights 



Group I 



Group II 



Group HI 



Age = 



Rate of growth 



Agei 



Rate of growth 



Age ■ 



Rate of growth 



* Counted from conception, age at birth being 9.4 mos. 



The change in composition with age and body weight. — In their study 

 of the changing composition of steers with age, the Missouri investigators 

 analyzed, in a very complete and careful manner, the carcasses of 11 

 steers from Group I, 10 steers from Group II, and 9 steers from Group 

 III, at ages ranging from 3 months to 4 years from birth. From the data 

 thus obtained, it is of great interest to establish a satisfactory mathe- 

 matical description of the relations between age and nitrogen content, 

 age and water content, age and fat content, and age and ash content in 

 these three groups of steers. 



In comparing the live and empty weights of the slaughtered animals 

 with their attained ages great irregularities are observable within each 

 group (see Mo. Res. Bull. 55, Table 79). This is not a matter of 

 surprise, in view of the small numbers of animals slaughtered in each 

 group, and is probably due to a variable food consumption. Before 

 attempting a mathematical analysis of these data, it appears desirable 

 to remove some of this irregularity if a legitimate plan is at hand. The 

 percentage composition of an animal is undoubtedly more closely related 

 to the weight attained than to the age of the animal. The differences in 

 the composition of animals, except for the very immature animal, are 



