2 BULLETIN 1372, U. S. DEPARTMENT OF AGRICULTURE 
SCOPE OF THE STUDY 
The following questions are discussed in this bulletin in connection 
with the comparative records of daughters and their dams, which are 
given in Tables 2 to 25, inclusive. 
1. What is the method of inheritance of production of milk and 
butterf at in dairy cattle ? Is it through the factors determining pro- 
duction, contributed by each parent ? Is it a blending inheritance — 
are the records of the daughters of a sire an average between his 
inherent transmitting ability and that of the dam of the daughter? 
2. Can a sire be prepotent or dominant in impressing his charac- 
teristics, or his standard of production, on his daughters regardless 
of the standard of production of the dams of those daughters ? 
3. Can a sire be prepotent in influencing both the milk yield and 
the percentage of butterf at? 
4. What influence has the dam's producing ability and the method 
of breeding on the prepotency of the sire ? 
5. Which parent has the greater influence on the yield of milk? 
Which has the greater influence on the percentage of butterf at in the 
milk? Is this percentage of butterf at correlated with or independent 
of the milk yield ? 
6. Which is the greater sire — one that sires daughters capable of 
making much larger records than their medium-producing dams, or 
one that sires daughters capable of slightly larger, or, at least, as large 
records as their high-record dams ? 
HOW THE SIRES WERE SELECTED 
In the list of 126 Holstein-Friesian sires given in another study (1) 
just 20 sires had 6 or more yearly record daughters whose dams also 
had yearly records. There were only three other sires in the breed, 
outside the above-mentioned list, up to Volume 29 of the Advanced 
Kegister Yearbook, that came within the category mentioned. The 
records of the daughters of these 23 sires, compared with their dams' 
records, provide the best material available in the Holstein-Friesian 
breed for the study of the transmitting ability of the sire. In choos- 
ing these sires for study the minimum number of six daughters was 
decided upon because it was felt that this number was the smallest 
which could be used in drawing conclusions relative to the correlation 
between the production of the daughters of any one sire and the pro- 
duction of their dams. 
In checking over the records of the daughters of these 23 sires it 
was found that 1 of the 6 daughters of 1 sire had a record of 568.3 
pounds of butterfat in 305 days, while her dam's record was 350.8 
pounds of butterfat made in 207 days. These records did not offer 
a fair comparison and were not included. Consequently, one of the 
sires appearing in the records has only five daughters with yearly 
record dams. Three of the 23 yearly record daughters of another 
sire were taken out for the same reason. 
To facilitate the study of the comparative records of the daughters 
and their dams, the milk as well as the butterfat was computed to 
maturity, when the records were made under 5 years of age. Table 
1 gives the percentages and ages used in calculating records to 
maturity. 
