132 Maine Agricultural Experiment Station. 1917. 



4. THE ANALYSIS OF MILK RECORDS. 



The intetisive study of existing records of milk and butter 

 fat production published in the Advanced Registry reports of 

 the various breeds has been prosecuted energetically during 

 the past year. As was pointed out in the last report, the neces- 

 sary age correction factors for milk production have now been 

 completely worked out for the three breeds, — Jersey, Holstein- 

 Friesian, and Ayrshire. The necessity for these age correc- 

 tions has been emphasized in former reports. Before it is pos- 

 sible to make any just comparison between the productivity 

 of two cows it is necessary that a proper scientific correction 

 be made for their difference in age at the time when the milk 

 records were made. The working out of proper corrections 

 has involved a great deal of extremely laborious mathematical 

 work. This work, however, is now completed and we are able 

 to use these correction factors in a constructive way. 



As a first contribution in this direction we have considered 

 in the Jersey breed the influence of certain advanced registry 

 bulls on the productive qualities of the breed. A complete 

 report on this phase of the work, which will include data cor- 

 responding to those for Tables 3, 4, and 5 for every Register 

 of Merit bull of the Jersey breed having two or more daughters 

 whose dams have records, will be issued as an appendix to this 

 report as soon as it can be prepared for the press. 



Tables 3, 4, and 5 show in abbreviated form the effect of 23 

 of the best known Jersey sires on the average milk, fat test, and 

 net butter fat production of their daughters as compared with 

 the dams of these daughters. It appears from these tables 

 that about one-half of the bulls in this group got daughters 

 which on the average were poorer producers than the dams of 

 those daughters. In some cases the deleterious effect of the bull 

 on the productive qualities of his offspring was extremely 

 marked. On the other hand, certain of the bulls in this group, 

 notably Hood Farm Torono, exercised an extraordinarily benefi- 

 cial effect upon the productive qualities of the breed. 



