130 



Maine Agricui^tural Experiment Station. 1917. 



3. THE CONTROL OF THE SEX RATIO. 



One of the primary objects for which the cooperative re- 

 cord project was inaugurated was to collect statistics bearing on 

 the question as to whether the proportion of males to females 

 in cattle could be influenced or controlled by the time of service 

 relative to the beginning of the period of heat. Some earlier 

 statistics^ appeared to indicate that there was a possibility of 

 influencing the sex ratio by paying attention to this point. It 

 was believed to be of such extreme importance as to justify the 

 careful study of the matter on the basis of much more extended 

 statistics. These statistics we have now collected and analyzed 

 and shall publish as soon as possible. In the meantime it may 

 be reported that, with the more extended statistics in hand, it 

 appears to be conclusively established that there is no definite 

 or permanent relation between the time in the heat period at 

 which the cow is served and the sex of the offspring. The ap- 

 parent relation between these two factors, which is believed by 

 many breeders to exist and which our earlier statistics appeared 

 to indicate, seems now to be purely accidental, and to have arisen 

 only because of the comparative meagerness of the statistics 

 on which the matter was discussed. 



TABLE 2. 



Shoiving the Sex of the Calves Following Service at 

 Different Parts of the Heat Period. 





Lapsed time in hrs. from 



appearance of heat to 



service. 



Sex of Offspring 



Per Cent 

 of 

 Males 



Heat Period 



MalHS 



Females 



Early 



Middle 



Late 



Under 3 hours. 



Over 3 and under 8 hours 



Over 8 hours 



200 

 270 

 187 



192 

 252 

 212 



51.0 

 51.7 

 46.9 



Totals 





657 



656 



50.0 



°Cf. Pearl, R., and Parshley, H. M. Sex Studies V. —Data on Sex 

 Determination in Cattle. Biol. Bulletin, Vol. 24, pp. 205-225, 1913. 



Pearl, R. Brief Report of Progress on Animal Husbandry Investi- 

 gations in 1914, Me. Agric. Expt. Sta. Misc. Publ. 503, pp. 1-11, 1914, 



