INFLUENCE OF STAGE OF LACTATION. 139 
During the first eleven weeks one cow returned a pound 
of butter fat to 3.79 pounds of net nutriment, and lost daily 
in weight 2 pounds, while another cow required 4.10 
pounds and lost 1.4 pounds daily in weight. That from the 
5th to 18th week one required 5.34 pounds of nutriment to 
a pound of butter fat and shrunk in weight .30 of a pound 
daily; another from the 9th to the 23rd weeks required 5.85 
pounds of net nutriment to a pound of butter fat and gained 
.10 of a pound daily; another from the 29th to the 42nd 
week returned a pound of butter fat to 6.12 pounds of avail- 
able nutriment; that from the 29th to the 132nd week there 
was little change in nutriment requirements to a pound of 
butter fat, the range being from 6.12 to 6.35 pounds, and 
that if a cow is fed more nutriment than she needs normally 
for dairy products she will convert the surplus to gain in 
weight. During the early stages of lactation she may return 
more than twice the product that the net nutriment would 
provide for, undernormal working condition of body weight. 
If a cow is in good condition when she drops her calf, the 
yield is largely in excess of the nutriment supply in the ra- 
tion, and will be in excess until she has milked down to nor- 
mal weight, after which the nutriment required to a pound 
of butter fat will remain quite constant for an indefinite 
time under proper management. 
It has beenshown that the rate of decrease in live weight 
when cows arefresh in milk varies with different individuals, 
and that it gradually decreases as the period of lactation 
advances. Also that the excess of yield in dairy products 
decreases from week to week until the yield, especially of 
butter fat, is fully provided for by the available or net nutri- 
ment consumed; but that the excesss of yield in total solids 
is prolonged for a time after astationary body weight is 
reached. To further illustrate this peculiar phenomena, and 
to show the average rate of increase in nutriment require- 
ments for a pound of butter fat and a pound of total milk 
solids, as the lactation period advances, a table is submitted 
showing the average weight after calving of 15 cows, their 
average weekly weight for the first nine weeks, their average 
daily yield of butter fat for each week and net nutriment to 
