206 Maine Agricultural Experiment Station. 1918. 



breeds, the Guernsey. As previously pointed out in other re- 

 ports, a knowledge of these correction factors for a given breed 

 enables a direct comparison of the milk records made at dif- 

 ferent ages through the use of these factors to correct the re- 

 cords of said animals to their expected maximum. The work- 

 ing out of these correction factors for the Guernsey breed 

 entailed the expenditure of a good deal of time and energy. 

 This work is now completed and the correction factors have 

 been used constructively to determine the influence that certain 

 sires have had on the Guernseys as a breed. For this those 

 sires are chosen which have had 2 or more of their daughters 

 from advanced registry dams, tested. The total number of bulls 

 which have this information is 272. As this report is a record 

 of progress rather than a tabulation of complete results, it 

 seems best that only a limited number of such sires be given 

 and the complete list be reserved for a separate bulletin when 

 a more adequate discussion may be given. 



Before pointing out the immense practical bearing of this 

 table on the selection and up-build of the herd, a few limitations 

 of its use as it stands in the present paper, should be discussed. 

 The table takes no cognizance of the absolute milk production 

 of the dams; it only concerns itself with the question of whether 

 the dam's record was higher than that of the daughter's. The 

 importance of recognizing this point is best brought out by an j 

 ■example. It is altogether probable that a bull going into a herd 

 composed of May Rilma's would have a harder time to raise 

 the milk production of his daughters than he would if he went 

 into a herd composed of 4000 pound cows. As a general influ- 

 ence on the herd the bull in the May Rilma herd might be a 

 distinct failure and in the 4000 pound herd a great success. It 

 would very possibly be true that from the breeds point of view 

 it would be wise to transfer the failure of the May Rilma herd 

 to the 4000 pound herd. For the man who had the May Rilma 

 herd it would be wise, in any case, to get rid of the bull failing 

 to maintain the production of his young stock. 



Tables 1, 2, and 3 show the effectiveness of 37 Guernsey 

 bulls in raising the production of milk, butter-fat per cent, and 

 butter fat in the milk of their daughters. Each of these bulls 



