PROTEIN REQUIREMENTS OF CATTLE: MITCHELL 23 



and was therefore used throughout. The equations found to give the best 

 fit ' to the various sets of data are as follows : 



In each case W is the total weight in kilograms of the constituent in 

 question at the age t, the latter being counted in months from concep- 

 tion. The fit of these equations to the experimental data is fully revealed 

 in Tables 9, 10, 11 and 12, in which, observed and calculated values for 

 each steer are compared. 



The fits appear to be good with the occasional exception of the youngest 

 one or two steers in a group, the general tendency being to underestimate 

 the nutrient content of these animals. 



Using the equations just given, the average composition of the steers 

 at regular intervals of time may be computed (see Table 13), and from 

 these figures the percentage composition of the steers (see Table 14). 



^ The constants were chosen in such a way that the sum of the squared residuals 

 was the least. 



^ The relation of the fat content of the cattle to their corrected age was found to 

 be very nearly linear, particularly for Group I, less so for Group II, and still less so 

 for Group III. With the Group I cattle, in fact, an appreciably better fit was 

 obtained by the use of the linear equation : 



W = 7.932t - 100.6 



than by the use of the exponential equation of Brody. Hence, in Table 11 the 

 calculated fat contents of the cattle of Group I have been obtained from the 

 linear relation. 



