654 
Journal of Agricultural Research 
Vol. XI, No. zs 
great as for the Holstein cows, but much greater than for the Jersey cows 
but the data are less conclusive because of the relatively small number of 
animals involved. 
The fact that certain of the animals of the Jersey and Holstein breeds 
whose records are included in the data comprised an experiment to deter¬ 
mine the influences of the plane of nutrition during growth and age of 
first calving upon the dairy qualities of cows (/) suggested that these two 
factors may have contributed to the difference in the character of the 
data from the two breeds. If a low plane of nutrition during growth 
should have a depressing effect upon the percentage of fat in the milk 
during the first lactation period, as one might expect, this fact would 
explain to a certain extent why the few animals with the greatest num¬ 
ber of lactation periods showed the greatest tendency to have a higher 
test in the second than in the first period. These animals comprise the 
oldest animals in the herd; and it is known to be a fact that the heifer 
calves were not reared on nearly so high a plane of nutrition during the 
earlier days of the herd than has been practiced in recent years. It may 
be stated in this connection that the records of the Jersey herd have been 
kept continuously for a period of 25 years. 
The data for the first two lactation periods of the Jersey and Holstein 
cows used in the above-mentioned experiment have been tabulated in 
Tables III and IV with respect to the two factors (1) age at first parturi¬ 
tion and (2) plane of nutrition during growth. 
The data bearing on the age of first parturition, shown in Table III, 
indicate that a difference of 16 months between the first parturition of 
the Jerseys had little influence upon the breed tendency already noted 
for the higher test to accompany the second lactation period. In the 
case of the Holsteins, however, calving at a more advanced age seemed 
to decrease the breed tendency for the first lactation period to show the 
higher average test. 
Table III .—Influence of age at first parturition on percentage of fat in milk of first two 
lactation periods 
Group 
No. 
Num¬ 
ber of 
cows. 
Breed of cows. 
Average 
age at 
first 
parturi¬ 
tion. 
Fat in milk. 
Cows showing highest test 
in— 
First 
period. 
Second 
period. 
First 
period. 
Second 
period. 
Station¬ 
ary. 
Months. 
Per cent . 
Per cent . 
Per cent. 
Per cent. 
Per cent. 
I. 
22 
Jersey. 
21. I 
5.04 
5 - 05 
31.8 
45-5 
22. 7 
2. 
21 
27. I 
5. IO 
5 -13 
3 °*° 
70. 0 
0. 0 
3 . 
l6 
.do. 
3 1 * 5 
5-09 
4.98 
62.5 
31. 2 
4 . 
14 
37*6 
5 -17 
5 - 32 
35 - 7 
50. 0 
14-3 
5 . 
4 
Holstein. 
22. 5 
3 - 29 
3.00 
IOO. O 
0. 0 
0. 0 
6. 
12 
.do. 
3 1 - 1 
3. 21 
3 - 17 
57-3 
16. 7 
25. 0 
7 . 
9 
35-4 
3 - 19 
3 -oS 
66. 7 
11. 1 
22. 2 
