PROTEIN REQUIREMENTS OF CATTLE: MITCHELL 69 



Tentative estimates of the total requirements of calves for digestible 

 protein of definite biological value, compared with Armsby's stand- 

 ards. — It will be of interest to compare estimates of the digestible protein 

 requirements of calves of different weights and breeds, as thus obtained 

 from the data developed in this report, with the digestible protein re- 

 quirements of the Armsby feeding standard, which in turn were taken 

 from Kellner's standard. Such a comparison is made in Table 31. 



It should be emphasized that the estimates in Table 31 based upon the 

 information developed in this report (see Table 23, and page 11) are 



TABLE 31 



Thk Requirements of Digestible Protein by Growing Calves According to the 

 Data Developed in this Report, as Comp,\red with the Armsby Standards 



* In terms of true protein. 



^ On the assumption of a biological value of .50 for the dietary protein. Since the biological value 

 is determined from the utilization of the total nitrogen of the ration, the estimated requirements 

 obtained by the use of biological values refer to crude protein. 



estimates of protein requirements for rates of growth equal to those ex- 

 hibited by the Missouri Hereford-Shorthorn calves of Group II, and by 

 Eckles' various groups of dairy heifer calves. If these calves did not grow 

 at normal rates, then the estimates of protein requirements are corres- 

 pondingly too low. 



It will be noted that the estimates given are much lower than the 

 Amisby standards, generally 50 per cent or more lower.' Can such low 

 estimates of the protein requirements of calves be reconciled with the 

 general trend of modern investigations, or must they be considered the 



* The difference is really greater than appears from the figures themselves, since 

 the Kellner- Armsby standards refer to digestible true protein, but the estimates 

 from this report refer to digestible crude protein (NX6.25). 

 5 



