The Bull as One Cause of Delayed Returns to Service in Artificial Breeding

In an earlier report (11) age of extended semen was implicated as contributing to the magnitude of the difference between 1-mo. and 5-too. non-returns to service. While it is not known that pregnancy actually was initiated in the cows involved, from the careful work of Tanabe and Casida (12) with cows of low fertility it may be inferred that such was the case. Consequently, these delayed returns to service are considered as indirect evidence for early embryonic mortality.. It is the purpose of this report to give the results of studies designed to determine the extent to which the bull may be responsible for delayed returns to service in artificial breeding and, by inference, a contributor to embryonic mortality.