72 
Journal of Agricultural Research voi. xiv, No. 2 
HOLSTEIN-FRIESIAN 
Tables XI to XIV exhibit the distributions of individuals with regard 
to the yield of milk and the percentage of fat in the form of correlation 
tables. Table XV combines Tables XI to XIV. Table D summarizes 
the means, standard deviations, coefficients of variability for milk and 
fat, and the correlations between percentage of fat and yield for Hol- 
stein-Friesians of different ages. 
Table D. — Summary of results from a study of the correlation between the percentage of 
fat and yield of milk for Holstein-Friesians 
[Fat in percentage; milk in pounds] 
Age. 
Years. 
2 to 3 
3 to 4 
4 to 5 
5 and over 
AH ages . . . 
Num- 
ber of 
ani- 
mals. 
292 
682 
Type of 
test. 
/Milk 
\Fat. 
Milk 
Fat. 
Milk 
Fat. 
Milk 
Fat. 
/Milk 
\Fat. 
Mean 
12, 
488.5 ± 80. 
4 
2, 942. 
0 ±56. 
3.462± 0. 
008 
0 
294 ± 0. 
I3>938.S ±116 
5 
3,188 
0 ±82. 
3. 433± 0 
012 
0 
322± 0. 
14 
825.5 ±124. 
4 
3. 151- 
0 ±87. 
3-4I7± 0 
012 
0 
313 ± 0. 
16 
280. 0 ± 94 
4 
3.654 
S ±66. 
3.420± 0 
008 
0 
301 ± c. 
14 
443- I ± 56 
0 
3.640 
7 ±39- 
3.43S± 0 
005 
0 
30s ± 0. 
Standard 
deviation. 
4 
008 
9 
009 
7 
006 
6 
003 
Coefficient 
of 
variability. 
23. 56.-to. 48 
8. 5o±o. 16 
22. 87±o. 62 
9- 38±o. 24 
21. 25±o. 62 
9. i7±o. 26 
22. 45±o. 43 
8. 81 ±0.16 
25. 2I±0. 29 
8. 88±o. 10 
Correlation. 
}- 
}-° 
}-o. 
}-° 
. ii6±o. 027 
'. i6o±o. 039 
o88±o. 039 
I. ii5±o. 026 
I. i33±o- 015 
The correlations are much smaller for the Holstein-Friesian than for 
the two preceding breeds. They range from — o.o88±o.039 to — o.i6o± 
0.036. The first is not significant when judged by the probable error. 
The milk yields increase regularly from 12,488 pounds for the youngest 
class to 16,280 for the oldest. The percentages of fat remain practically 
constant for the different ages. (See fig. 2.) * 
AYRSHIRE 
Tables XVI to XIX are correlation tables for the different classes of 
Ayrshires. Table E gives means, standards deviations, coefficients of 
variability for milk and fat, and the correlations between percentages of 
fat and yield of milk. 
TablS E. — Summary of results from a study of the correlation between the percentage of 
fat and yield of milk for Ayrshires 
[Fat in percentage; milk in pounds] 
Age. 
Num- 
ber of 
ani- 
mals. 
Type of 
test. 
Mean. 
Standard devia- 
tion. 
Coefficient of 
variability. 
Correlation. 
Years. 
a to 3 
3 to 4 
4 to 5 
All ages 
343 
192 
160 
396 
1, 091 
fJIilk 
\Fat 
/Milk 
\Fat 
/Milk 
\Fat 
/Milk 
iFnt 
/Milk 
\Fat 
7,960.5 ±47.9 
4. oi6± O.OII 
9,179-5 ±86.1 
3-936± 0.014 
9,584-5 ±83-5 
3-9l9± 0.016 
10, 726. 0 ±67. I 
3.865± O.OII 
9,417-1 ±41-7 
3-933± 0.006 
1,314.5 ±33-9 
0. 3IO± 0.008 
1,769.5 ±60.9 
0.3I4± O.OII 
1,566.5 ±59-1 
0. 303± O-OII 
1,980.0 ±47- S 
0.3I3± 0.008 
2,044.4 ±29.5 
0. 3i8± 0.005 
16. 5i±o. 44 
7. 71 ±0. 20 
19. 28±o. 69 
6.35±o. 28 
16.34io.63 
7. 73 io. 29 
18. 46±o. 46 
8. loio. 19 
21. 7lio.33 
8.o8±o. 12 
|-l-o.oi9io.036 
|— 0. O93±o.048 
|— 0.023 ±0.053 
|— o.047±o.034 
|— 0. i38±o.030 
