2l6 AGRICUI^TURE OF MAINE. 



5. The physiology of cattle breeding, including: (a) The 

 normal duration of heat (oestrum) in cattle; (b) The length 

 of time a breeding cow is dry; (c) The age of breeding stock; 

 (dj Cystic degeneration of the ovaries. 



6. The inheritance of milk and butter fat producing ability. 

 During the past year, work on the investigation outlined in 



earlier reports has been prosecuted energetically. It is possible 

 to report definite progress along several lines at this time. In 

 presenting this report each of the general lines of investigation 

 going forward will be separately considered. 



I. The Study and Analysis oe Milk Records. 



During the past year the work in this direction has fallen 

 into three chief divisions, viz: (a) The preparation for the 

 press of the results of the extended study of the relation of 

 milk flow to age in dairy cattle; (b) The preparation of a 

 Dairy Efficiency Table; (c) The transfer and analysis of the 

 Biltmore herd records. 



(a) RELATION OF MILK FLOW TO AGE IN DAIRY CATTLE. 



The main essential results of this investigation were in hand 

 at the time of the last annual report. It has been possible to 

 demonstrate in the most complete manner from extensive data 

 on the three breeds, Jerseys, Holstein-Friesian, and Ayrshire, 

 that the change in milk-flow as a cow grows older follows a 

 definite law, expressible in the form of a mathematical equation. 

 A preliminary statement of this law has been published." 



The preparation of this material for printing has been a 

 laborious and time-consuming task. It is now hoped that,, 

 within a few months following this report, the complete manu- 

 script will be ready for the printer. In connection with the 

 preparation of this material for the press, a number of interest- 

 ing subsidiary matters have come to light. One may be briefly 

 considered here. 



»i 



*Pearl, R. On the Law Relating Milk Flow to Age in Dairy Cattle. 

 Proc. Soc. Exper. Biol, and Med., Vol. XII, pp. 18-19, 1914. 



