﻿TRANSMITTIlSrG ABILITY OF HOLSTEIN-FRIESIAK SIRES 



13 



the records of their dams -^dll 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 me 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 mherent transmitting 

 abihty 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 smn 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 m 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- 

 eaiceof 

 predicted 

 from 

 actual 

 produc- 

 tion 



1 



Pounds 

 705. 3 

 791.8 



Pounds 

 970.5 

 912.1 

 848.8 

 821.2 

 804. 5 

 784.2 

 745.0 



Pounds 

 -20.0. 2 

 -120.3 

 -89. 2 

 -1.3.5.0 

 -G9.6 

 —fjl',. 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 

 500.1 



Pounds 

 -59.8 



2 



9 



+04 3 



3 



7.59. fi 



10. _. 



+98.1 



4 685.6 



n. 



+93.8 



5 i 734.8 



12 



+265. 



6 



717.7 

 792.6 



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 pcrcontagc fat that 

 are intermediate between those of the two parents. In thes(; crosses 

 between distinct hn-cds then; ur(; proliably so many independently 

 inherited facUjrs having a bearing on the milk flow and the percentage 

 fat in each parent, that it is almost impossible to bring about, in any 



