Dec. 17,1917 
Influence of Age of Cow on Milk and Milk Fat 
649 
their records from this source. The data, therefore, include the records 
of animals of the Jersey, Holstein, and Ayrshire breeds only. 
The data showing the average percentages of fat for the successive 
lactation periods of all animals of each breed and similar data for the 
LACTATION PERIODS 
Fig. 2. —Graphs of the variation in percentage of fat of Holstein cows in successive lactation periods, and 
proportion of total number of cows in each group showing highest test in each period. 
entire herd are given in Table I. An examination of the records of the 
individual animals of each breed, which it would be impracticable to 
publish on account of their extensiveness, showed rather striking differ- 
ences among the breeds with respect to the frequency with which the 
