TKANSMITTING ABILITY OF HOLSTEIN-FMESIAN SIRES 
13 
the records of their dams will not be uniform; nor is the size of the 
record of the dam a criterion of the size of the record of the daughter. 
THE BLENDING-INHERITANCE THEORY 
Many investigators and breeders believe that the inheritance of 
milk and butterfat production is of the blending type. It has been 
suggested, in accordance with this theory, that the true measure of a 
sire s inherent ability might be calculated by adding the average in- 
crease of the daughters over their dams to the average record of the 
daughters, the result being the true inherent transmitting ability of 
the sire for milk and butterfat production. The assumption is that 
the capacity of the daughter is halfway between that of her sire and 
that of her dam. Thus, if the sire's inherent transmitting ability is 
800 pounds of butterfat and he is bred to a 600-pound-butterfat cow, 
the daughter should have the ability to make an average between the 
two, or 700 pounds of fat. 
This theory was tried out by taking the average butterfat records 
of the daughters of sire B and their dams. The average of the daugh- 
ters was 745 pounds of butterfat; the average of their dams was 581 
pounds of butterfat. The difference between the average of the 
daughters and the average of the dams was 164 pounds. This added 
to the average of the daughters gives the sire an inherent transmitting 
ability of 909 pounds of butterfat. With the inherent transmitting 
ability of the sire a known quantity, as is also the record of the cow 
to which he is mated, it should be possible to predict the producing 
capacity of a particular daughter by halving the sum of the sire's 
standard and dam's record, the resulting average being the daughter's 
producing capacity. But when this system is applied to the individ- 
ual daughters of sire B the results do not check well with the actual 
records in Table 2. The comparison is shown in Table 4. 
Table 4. — Butterfat records of daughters of sire B, showing butterfat production 
predicted by blending-inheritance computation, and that actually produced 
Daughter No. 
Butterfat 
predicted 
Butterfat 
produced 
Differ- 
ence of 
predicted 
from 
actual 
produc- 
tion 
Daughter No. 
Butterfat 
predicted 
Butterfat 
produced 
Differ- 
ence of 
predicted 
from 
actual 
produc- 
tion 
1 
Pounds 
705.3 
791.8 
759.6 
685.6 
734.9 
717.7 
792.6 
Pounds 
970.5 
912.1 
848.8 
821.2 
804.5 
784.2 
745.0 
Pounds 
-265. 2 
-120. 3 
-89.2 
-135. 6 
-69.6 
-66.5 
+47.6 
8 
Pounds 
678.8 
791.8 
786.4 
717.5 
783.5 
743.2 
Pounds 
738.6 
727.5 
688.3 
623.7 
517.9 
506.1 
Pounds 
-59.8 
2 
9 
+64 3 
3 
10.. 
+98.1 
4... 
11.. 
+93.8 
5 
12 
+266. 6 
6 
13 
+237.1 
7... 
It is true that where there have been crosses between two distinct 
breeds of dairy cattle that have a considerable difference between 
their milk flow and their range of butterfat percentage, such as the 
Holstein-Friesian cross on Guernsey or Jersey, it has been observed 
that the resulting progeny have a milk flow and a percentage fat that 
are intermediate between those of the two parents. In these crosses 
between distinct breeds there are probably so many independently 
inherited factors having a bearing on the milk flow and the percentage 
fat in each parent, that it is almost impossible to bring about, in any 
