BUTTERFAT PRODUCTION OF CATTLF 7 
In a total of 3,722 pairs of Jersey records studied, the develop- 
ment factor averages 11.0 per cent of the reentry record; and in 
1,215 pairs of Guernsey records an average of 12.2 per cent of the 
reentry record is due to development. 
Where the groups are sufficiently large to be significant, this factor 
of development is fairly uniform. Groups containing small numbers 
of individuals show the greatest fluctuations, which is to be expected. 
The tables do seem to indicate, however, that where the interval is 
very long between the initial and reentry records the development 
is more marked. This may be contrary to what would be expected, 
or it is possible that during the lapse of a considerable period of 
time there has been sufficiently marked improvement in methods of 
handling test cows to account for this greater development. 
There is sufficient evidence to prove that official testing develops 
the productive ability of dairy cows, and that the feeding and care, 
combined with the prolonged milking period during which the cow 
is encouraged to yield her utmost, have an appreciable and positive 
effect on her production during subsequent lactation periods. 
Table 5. — Comparison of average initial and retest records of Guernseys having- 
initial records made at age under 2 years {single-letter records) 
Num- 
Average 
initial 
butterfat 
record 
made 
under 2 
years old 
Average reentry records made at ages shown in these 
columns by same cows as initial records shown in 
column at left (pounds of butterfat) 
In- 
crease 
due to 
age 
Portion of 
reentry record 
due to 
development 
Aver- 
age due 
to de- 
ber of 
cows 
CO 
O 
co 
O 
CO 
o 
co" 
o 
o 
o 
o 

o 
to 
p 
CO 
o 
00 
o 
00 
o 
co 
o 
00 
o 
OS 
o 
c 
o 
© 
c 
o 
velop- 
ment 
for this 
group 
2 
Pounds 
295 
396 
358 
371 
388 
584 
383 
321 
407 
392 
321 
415 
311 
321 
393 
Pounds 
45 
70 
83 
103 
111 
197 
129 
108 
137 
132 
108 
140 
105 
108 
Pounds 
53 
45 
22 
64 
79 
-86 
47 
38 
27 
-38 
104 
48 
227 
-7 
P.ct. 
13.5 
8.8 
4.8 
11.9 
13.7 
-12.4 
8.4 
8.1 
4.7 
-7.8 
19.5 
8.0 
35.3 
-1.7 
P.ct, 
14 
511 
4 
463 
4 
538 
6 
578 
1 
09.- 
7 
559 
2 
467 
1 8. 11 
4 
571 
5 
486 
1 
533 
2 
603 
2 
643 
1 
422 
! 
