Data on Sex Determination in Cattle

In this paper statistics collected some years ago at the Maine Agricultural Experiment Station in regard to the relation between time of service in the œstrous period and the sex of the subsequent offspring in domestic cattle are subjected to biometric analysis. These statistics are much more extensive than any which have hitherto been collected for the study of this problem in cattle. It is shown: 1. That as the time of coitus approaches the end of the œstrous period there is a progressive increase in the proportion of male young born. 2. That in the extreme case this increase in the proportion of male births is probably statistically significant and not to be attributed to errors of random sampling. 3. That these modifications of the sex ratio cannot be attributed to age differences or to any other factor yet suggested. A possible explanation of the results and their practical bearings are discussed.