﻿2 BULLETIN 1372, U, S. DEPAETMENT OF AGRICULTUKE 



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 — (Wie that sires daughters capable of 

 making niuch 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 

 Register 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 facflitate 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. 



