The cow has been specifically selected for lactational performance. It has no lactational anoestrus and the simultaneous reproductive ability and milk yield have not only scientific interest but economic importance too. We have no evidence of a luteotrophic action of prolactin (Hoffmann, Schams, Bopp, Ender, Giménez & Karg, 1974) in this species such as has been shown in some others. Furthermore, mammary cancer, one motivation for the increasing amount of work devoted to studies on prolactin in man, has not been recorded in the cow.
RADIOIMMUNOASSAY FOR BOVINE PROLACTIN
In 1969, a specific radioimmunoassay for bovine prolactin using NIH-P-B2 (biological activity 19·9 i.u./mg) as antigen was developed (Schams & Karg, 1969). In this system there were no cross reactions with growth hormone or other pituitary hormones.