Dec. I, 1919 



Nitrogen Metabolism of Two- Year-Old Steers 



253 



to 27,41 per cent) may have been due to the smaller amounts of protein 

 received in this period, or to the increase in the age of the steers, or to 

 both. In period 3, when both the protein and energy were decreased, 

 some of the steers stored more and others less protein. However, in period 

 4, when the protein was practically doubled and the energy slightly 

 decreased, there was a considerable decrease in the percentage of protein 

 stored, except for one steer, No. 666. The results obtained in period 5 

 are so irregular as to be of little value, although with one exception, 

 steer 650, which was on full feed in this period, the results are usually 

 lower. In general, our results indicate that a smaller percentage of the 

 protein is retained as the age of the animal increases. As already pointed 

 out, however, the protein and energy consumption for different periods 

 varied, and this variation probably materially affects the value of our 

 results. 



Table VII. — Percentage of digested protein retained 



o steer 663 removed at end of thirtieth week. 



6 Steers 650, 666, and 652 were on full feed in period 5. 



* Not included in average of all steers. 



d Steer 652 removed at end of thirty-fourth week. 



A study of the results for all steers for the entire 37 weeks of the experi- 

 ment shows no distinctive differences between lots. In fact individual 

 differences are quite small, considering the nature of the experiment. 

 The results show that the eight steers stored from 18.92 to 25.06 per cent, 

 or an average of 22.37^ per cent, of the protein digested. 



SUMMARY 



(i) The results pertaining to the nitrogen metabolism of eight 2 -year- 

 old steers for a period of 37 weeks are given. 



(2) Steers maintained a positive nitrogen balance for long periods of 

 time when receiving considerably smaller amounts of digestible protein 

 than are usually considered necessary for maintenance. 



(3) Curves showing the nitrogen consumption, the total nitrogen 

 excretion, the urinary nitrogen, and the nitrogen balance are more or 

 less parallel. 



