l6 MAINE AGRICULTURAL EXPERIMENT STATION. 



with the writer of this Report. It is expected that the collectioii 

 of breeding records will be continued for at least one more 

 year. 



It appears desirable at this time to present brief statements 

 regarding certain of the results which have been reached from 

 the study of these records. This is done in Section IV of 

 this Report. Detailed publication will follow in due time in 

 another place. 



IV. Physiology oe Cattle Breeding. 



Here w^e shall consider certain topics based in part upon 

 the cooperative breeding records, and in part upon other 

 studies. 



I. THE NORMAL DURATION OE HEAT (oESTRUM) IN CATTLE. 



The cooperative breeding records furnish extensive data 

 bearing upon this point. Table 6 shows for various breeds 

 the number of hours which elapsed between (a) the time 

 when the breeder observed that the cow^ was in heat and (b) 

 the time when she was served by the bull. All of the services 

 recorded in this table were successful, i. e., the cow became 

 pregnant as a result of the recorded service, and either car- 

 ried the calf to term, or aborted at some time before term. 



