Bee. I?, 1917 Influence of Age of Cow on Milk and Milk Fat 
653 
Table II .—Relative distribution of highest average test for the lactation period —Con. 
AYRSHIRE COWS 
Number of cows. 
I,acta- 
tion 
periods. 
Proportion of cows showing highest test in period— 
i 
2 
3 
4 
5 
6 
7 
n . 
2 
55-5 
66.7 
55-5 
83-3 
83-3 
83-3 
75 -o 
75 -o 
75 -o 
50.0 
44 - 5 
33-3 
22. 2 
y . 
n . 
2 
y . 
n . 
3 
22. 3 
. . 
6 . 
0 
2 
16. 7 
16. 7 
16. 7 
25.0 
25.0 
25.0 
25.0 
6 . 
2 
0. 0 
6 . . . . 
O 
4 
0. 0 
0. 0 
T 
2 
A . 
7 
0. 0 
.. 
A . 
O 
4 
0. 0 
0. 0 
K 
0. 0 
25.0 
4 . 
4.1 
3.9 
3.7 
3.5 
----PER CENT COWS 
-PER CENT FAT 
9 COWS 
60 
40 
20 
0 
<* 
» 
o 
o 
lit 
o 
oc 
111 
CL 
LACTATION PERIODS 
Fig. 3.—Graphs of the variation in percentage of fat of Ayrshire cows in successive lactation periods, and 
proportion of total number of cows in each group showing highest test in each period. 
The data for the cows of the Holstein breed shown in Table II and 
figure 2 are in marked contrast to those for the Jersey breed. The 
chances for the highest fat test are so overwhelmingly in favor of the 
first lactation period that the conclusion seems justified that this is a 
breed characteristic. A similar tendency is shown by the data from the 
Ayrshire cows, shown in Table II and figure 3. The tendency is not so 
23718°—17 - 3 
