It is clearly evident why during days 592-594 a heavy nitrogen 

 deficit w'as recorded, since the "surplus" nitrogen, even without allow- 

 ance for digestibility, was barely greater than the nitrogen removed 

 from the body in the milk. Even in the period, days 595-603, when the 

 "surplus" nitrogen was roughly twice that secreted in the milk, equi- 

 librium was barely established, and again later, in the period, daj's 

 706-722, when a similar proportion prevailed, nitrogen deficit again set 

 in. In the intervening jjeriods when the proportion was well over 3:1a 

 substantial nitrogen-retention was effected. 



It would appear therefore that in order to prevent loss of nitrogen 

 from the body of the lactating cow the "surplus" nitrogen must amount 

 to well over twice the amount of nitrogen secreted in the milk. This is a 

 condition which may well be difficult to satisfy in practice. Cow D was 

 only a moderate milker (about 28 lb. milk daily at maximum), and yet 

 it required the heavy and highly nitrogenous rations indicated to prevent 

 loss of nitrogen from the body. With the more liberal milk-flow so often 

 achieved with the modern dairy cow it would be even more difficult to 

 secure nitrogen-equihbrium, if not indeed beyond the food-consuming 

 capacity of the cow. This is fully in accord with practical experience of 

 the difficulty of maintaining the "condition" of the milch cow in the 

 early stages of lactation. 



The full details for Cow C (dry and not in calf) are not given for this 

 period, as they present no new features of interest. The establishment 

 of a po.sitive nitrogen balance is noteworthy, since on the same ration 

 in the preceding period, a decided negative balance was recorded. An 

 examination of the figures for the complete trial shows, however, that 

 Cow C had been able to store about 1000 gm. of nitrogen from the 

 81,000 gm. consumed. 



