PROTEIN REQUIREMENTS OF CATTLE: MITCHELL 37 



respect to the weight-height relation. Thus, a lO-month-old Holstein 

 heifer possesses the same weight-height relation as a 15-month-old 

 Jersey, 



The steers of Groups I, II and III, although differing markedly in 

 their age-weight relationships, were strikingly similar in their age- 

 height relationships, indicating that skeletal growth, at least, was ver}* 

 little affected by the plane of nutrition. Thus, at 4 years of age, the 

 average height at withers for all groups was very close to 56 inches, 

 although the average weights were, in order, 1945, 1238, and 897 pounds. 



If the height-weight relation of these beef steers is compared with that 

 of the dairy heifers cited by Brody and Eagsdale, it becomes evident that 

 a better agreement exists between the Group II steers and the dairy 

 heifers than between either the Group I or the Group III steers and the 

 dairy heifers. Thus, at a height of 40 inches, the dairy cattle weighed 

 about 365 pounds, while the steers of Group I weighed about 415 pounds, 

 those of Group II about 415 pounds, and those of Group III about 320 

 pounds. At a height of 45 inches, the dairy cattle averaged about 550 

 pounds in weight, while the steers of Group I averaged about 710 pounds, 

 those of Group II about 595 pounds, and those of Group III about 450 

 pounds. For a height of 50 inches, the dairy cattle weighed 855 pounds, 

 the Group I steers 1070 pounds, the Group II steers 810 pounds, and 

 the Group III steers 605 pounds. For greater heights, the Holstein 

 heifers weighed increasingly more than the Group II steers, though far 

 less than the Group I steers. From this comparison, it appears evident 

 that the nutritive condition of the steers of Group II was kept approxi- 

 mately the same as that of growing dairy heifers of equal height, except 

 at the greater heights (above 50 inches) where the condition of the 

 dairy cattle (Holstein only) was superior to that of these steers. 



This constitutes confirmatory evidence that the body changes occurring 

 in the steers of Group II, approximate what might be considered normal 

 growth changes. If this is true, then the changes occurring in Group III 

 represent subnormal growth changes and need not be considered further 

 in this discussion of the protein requirements of growth and fattening. 

 It is a matter of interest, however, to investigate the difference in nitro- 

 gen content and in the rate of nitrogen deposition between Group II and 

 Group I, as revealed in Tables 13 and 16. The steers of Group I con- 

 tained on an average a larger amount of nitrogen at all ages, and for the 

 first two years averaged a greater rate of nitrogen deposition. Are these 

 differences due only to a greater rate of gTowth in Group I than in 

 Group II, or are they due in part at least to the greater rate of fatten- 



