Reproductive anatomy and cytogenetics of freemartin heifers.

Out of a batch of 46 heifers obtained for breeding 19 were found to be freemartins by both anatomical and cytogenetic examination. Considerable variation existed in the reproductive tracts of these freemartins from structures that were essentially female to some that were essentially male in type. One heifer had a functional ovary containing a corpus luteum and had shown signs of oestrus. Sex chromosome chimaerism was detected in cultured leucocytes and in bone marrow from each of the freemartins, ranging from 2 per cent to 96 per cent male cells. Chimaerism was also detected in cell cultures from spleen, lung and gonad but at very low levels (less than 2 per cent male cells). None of the freemartins consistently showed the presence of male cells in all organs cultured. The problem of the clinical diagnosis of freemartins is discussed in relation to these results.