BUTTERFAT PRODUCTION OF CATTLE 
Tables 1 and 2 show what proportion the average production at 
any age is of the average mature production. 
Table 1.- 
-Initial records at various ages of single-letter advanced-register Guernsey 
cows 
Age (years) 
Number 
of 
records 
Average 
produc- 
tion of 
butter- 
fat 
Percent- 
age that 
produc- 
tion at 
this age 
is of 
average 
mature 
produc- 
tion 
Age (years) 
Number 
of 
records 
Average 
produc- 
tion of 
butter- 
fat 
Percent- 
age that 
produc- 
tion at 
this age 
is of 
average 
mature 
produc- 
tion 
Under 2 
275 
2,367 
1,211 
897 
695 
625 
432 
373 
313 
305 
214 
179 
148 
135 
88 
Pounds 
368 
404 
424 
433 
453 
470 
473 
495 
489 
482 
487 
495 
499 
496 
495 
Per cent 
74.8 
82.1 
86.2 
88.0 
92.1 
95.5 
96.1 
100.6 
99.4 
98.0 
99.0 
100.6 
101.4 
100.8 
100.6 
9to9M— - - 
102 
80 
45 
27 
28 
15 
13 
8 
10 
8 
3 
3 
1 
1 
1 
Pounds 
502 
496 
493 
486 
459 
456 
504 
475 
454 
494 
417 
456 
395 
458 
364 
Per cent 
102.0 
2 to 2^ 
9J^to 10 
100.8 
2^6 to 3 
lOtolOH 
100.2 
3 to3H 
10^ to 11 -- 
98.8 
3J/£ to 4 
11 to 11^„„ 
93.3 
4to4H 
11^ to 12 
92.7 
\ X A to 5 
12 to 12}^ --- 
102.4 
5 to 5H 
12^ to 13... - 
96.5 
5Hto6 
13tol3H 
92.3 
6 to §y 2 
13^ to 14 
100.4 
6}/>to7 
14tol4^ 
84.8 
7 to IVi 
15 tol5H 
92.7 
7Hto8 
16^ to 17. 
80.3 
8 to %y 2 
17 to 17J4 
93.1 
8> 2 to-9 
17J4 to 18 -•— 
74.0 
Table 2. 
-Initial records at various ages of class A and class A A register-of -merit 
Jersey cows 
Age (years) 
Number 
of 
records 
Average 
produc- 
tion of 
butter- 
fat 
Percent- 
age that 
produc- 
tion at 
this age 
is of 
average 
mature 
produc- 
tion 
Age (years) 
Number 
of 
records 
Average 
produc- 
tion of 
butter - 
fat 
Percent- 
age that 
produc- 
tion at 
this age 
is of 
average 
mature 
produc- 
tion 
Under 2 . 
1,237 
3,633 
1,313 
1,298 
1,011 
924 
705 
673 
587 
509 
404 
395 
310 
267 
232 
163 
Pounds 
343 
368 
386 
404 
423 
440 
454 
457 
469 
475 
471 
468 
470 
480 
462 
468 
Per cent 
72.7 
78.0 
81.8 
85.6 
89.8 
93.2 
96.2 
96.8 
99.4 
100.6 
99.8 
99.2 
99.6 
101.7 
97.9 
99.2 
9^to 10 
128 
114 
68 
53 
39 
40 
16 
18 
11 
6 
6 
2 
4 
2 
2 
1 
Pounds 
475 
476 
459 
454 
478 
445 
436 
445 
475 
439 
424 
412 
405 
437 
391 
401 
Per cent 
100.6 
2to2^ 
10 to \0V 2 
100.8 
zy 2 to 3 
103^ to 11 
97.2 
3to3H 
lltollH 
96.2 
V/i to 4 
i\y 2 to 12 
101. 3 
4to4H 
12 to 12J6 
94.3 
4^to5 
12J/2 to 13 
92.4 
5to5H- 
13 to 13H 
94.3 
5Hto6 
133^ to 14 
100.6 
6 to 6^ 
utouy 2 
93.0 
6J^to7 
14^ to 15 
89.8 
7to7H 
15 to ny 2 
87.3 
iy 2 to% 
lby 2 to 16 
85.8 
8to8J/2 
16 to 16H 
92.6 
8Hto9 
16V£ to 17 
82.8 
9to9H 
18 to 18H 
85.0 
'The data studied do not show that there is a definite age at which 
all cows reach their maximum producing ability. For both Guernsey 
and Jersey cattle there is a period of years during which the average 
production of animals in the various age groups shows only slight 
variation. These fluctuations have no decided trend, and this entire 
period is included in the age of maximum production. The Jersey 
cows seem to reach maturity at 6 years of age, and there is no decided 
decline in average production until after the age of 10^ years. 
There are 2,522 initial records in this period, according to Table 2, 
