Interest in the element selenium with respect to its biological significance has been steadily increasing for the last ten
years. Neutron activation analysis has long been used for the accurate determination of selenium in biological samples usually
via75Se. More recently activation analysts having access to high flux reactors with rapid delivery pneumatic tube facilities; have
successfully employed77mSe. This approach, which is much faster, is particularly well suited to the Missouri University Research Reactor (MURR). The
specific interest concerning bulls has to do with the involvement of selenium in the reproductive system. Selenium analysis
methodology and data on plasma, semen and 22 tissues from both beef and dairy bulls are presented.