226 AGRICULTURE OF MAINE. 



At this time we wish to take occasion to thank most heartily 

 the members of this association who have so kindly cooperated 

 in this work. We realize that it is some trouble to the breeder 

 to fill out these blanks and that when he does it, it is without 

 any thought of immediate personal gain, but from the altruistic 

 motive of helping along the general knowledge of the laws of 

 breeding in dairy cattle. We are extremely grateful to those 

 who are helping us and should be very glad to have as many 

 more volunteer cooperators as possible who may care to take 

 part in the work. Details in regard to this plan may be obtained 

 by writing to the Maine Agricultural Experiment Station. 



4. THE RELATION OF THE TIME OF SERVICE TO THE SEX RATIO 



IN CATTLE. 



One of the primary purposes for which the cooperative cat- 

 tle breeding record plan discussed in the preceding section was 

 undertaken was to get comprehensive statistics to show whether 

 any definite effect on the proportion of male and female calves 

 born could be observed when service occurred at dififerent times 

 in the heat period. Earlier work done at the Station some 

 years ago indicated that when service occurred very early in 

 heat there was likely to be born a larger proportion of heifer 

 calves, and when service occurred very late in heat there was 

 likely to be born a larger proportion of bull calves. With a 

 hope of getting a very much larger amount of more precise 

 data on this point, the cattle breeding record plan was inau- 

 gurated. The results to date have been very gratifying. The 

 following table shows the sex of the calves on which exact 

 records of time of service have been had up to date. 



Bulls to 

 Bull calves Heifer calves 1000 heifers 

 Service early in heat... 160 243 658 



Service in middle of heat yj 69 11 16 



Service late in heat.... 97 52 1865 



Totals 334 364 



From this table it is clear that there is a very striking differ- 

 ence in the result according to whether service is early or late 

 in heat. This difiference is already well beyond the bounds of 



