BUTTERFAT PRODUCTION OF CATTLE 5 
Table 4. — Distribution of initial records of class A and class A A Jersey cows, 
according to age 
Age 
Pounds of butterfat 
Under 
2 years 
2 
years 
3 
years 
4 
years 
5 
years 
6 
years 
7 
years 
8 
years 
9 
years 
10 years 
and 
older 
Total 
250 to 274 
172 
183 
226 
172 
162 
119 
67 
53 
31 
12 
15 
9 
6 
4 
1 
2 
1 
231 
611 
744 
726 
734 
618 
454 
328 
244 
173 
125 
90 
53 
43 
26 
15 
13 
9 
4 
1 
3 
403 
275 to 299 
29 
211 
327 
344 
340 
311 
224 
192 
114 
97 
63 
41 
33 
25 
20 
16 
8 
5 
4 
3 
823 
300 to 324 
1 
94 
213 
233 
215 
198 
185 
139 
109 
64 
63 
36 
32 
17 
9 
4 
9 
3 
2 
1,182 
325 to 349 
1,319 
350 to 374... 
129 
173 
187 
176 
146 
121 
84 
67 
45 
40 
32 
16 
12 
10 
10 
3 
5 
1 
2 
78 
129 
136 
111 
84 
76 
78 
46 
48 
33 
31 
20 
11 
8 
10 
5 
1 
5 
1 
1 
54 
101 
117 
97 
66 
64 
57 
32 
29 
24 
21 
8 
9 
5 
9 
3 
1 
3 
4 
...... 
31 
62 
80 
62 
61 
56 
37 
35 
23 
12 
7 
13 
7 
1 
5 
3 
1 
1 
2 
19 
41 
48 
44 
33 
23 
15 
22 
9 
9 
9 
5 
2 
3 
4 
2 
53 
49 
59 
49 
38 
42 
26 
14 
10 
11 
5 
11 
5 
2 
4 
1 
1,817 
375 to 399 
1,865 
400 to 424 
1,674 
425 to 449. 
1,342 
450 to 474 
1,080 
475 to 499 
820 
500to524 
643 
525 to 549 .. 
442 
550 to 574 
327 
575 to 599 _. 
245 
600to624 
189 
625 to 649. . 
127 
650to674 
85 
675 to 699.. 
50 
700to724 
60 
725 to 749. . 
25 
750 to 774. 
16 
775 to 799 
...... 
1 
11 
800 to 824 
1 
1 
1 
I" 
1 
2 
12 
825 to 849 
7 
850 to 874. 
1 
2 
875 to 899 
900 to 924. 
1 
1 
925 to 949 
1 
1 
950 to 974.. 
1 
1 
2 
975 to 999 . 
1 
1 
Total.. 
1,237 
5,246 
2,409 
1,629 
1,260 
913 
705 
499 
291 
382 
14, 571 
THE FACTOR OF DEVELOPMENT 
In studying the official-test records of animals grouped according 
to age it is apparent that in advancing from class to class there is 
some influence at work, other than age, which causes an increase 
in production. A comparison of the tables of initial records with 
those made up of both initial and reentry records brings this point 
out clearly. It is also brought to our attention in comparing records 
made at advanced ages by the same individuals, after age itself has 
ceased to bring about a further increase in production. With very 
few exceptions cows which made their initial records after reaching 
maturity have increased these records when tested again. 
The first grouping of animals to study the influence of age on 
production was made only from animals having two or more records. 
It was found that because of the influence on the second record of 
the development made by the animal during the initial test, these 
retest records did not offer a correct indication of the effect on pro- 
duction of advance in age; but, when compared with the average 
initial records made for each age class, these retest records do show 
the apparent influence on later records of the development made 
by the animal during the first test. 
Tables 5 to 21, inclusive, show the average initial and retest records 
of all Guernsey and Jersey cows having two records. A study of 
these tables will show the manner in which the animals are grouped. 
In Table 5, for instance, all the cows made their initial records under 
