Plasma oestradiol-17\g=b\ concentrations rise slowly in the late progestational phase of the bovine oestrous cycle before plasma progesterone levels fall and then rise rapidly to a pre-oestrous peak of about 6 pg/ml as progesterone levels fall rapidly. The oestradiol-17\g=b\ level (on average) falls during oestrus and both steroids show minimum levels 1\p=n-\2 days after oestrus. Both then rise again, oestradiol-17\g=b\ to a second peak 6\p=n-\7 days

No abstract

A case of intersexuality in a Dorset horn ewe is described. Although possessing female external genitalia this animal had a male internal reproductive tract with inguinal testes, epididymes, vasa deferentia and seminal vesicles. No traces of cervix or uterus were present and the vagina was represented in its caudal part only. Chromosomal studies revealed chimaerism in peripheral leucocytes of the type 54, XX/54, XY, while other tissues revealed the normal female karyotype 54, XX. The ewe was born in a set of triplets with one dead male fetus and one living male. It was therefore concluded that the animal was a freemartin. The significance of this case and of the phenomenon of freemartisism in sheep is discussed.

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.

Thirty-four heifers not conceiving to three or more inseminations or natural service were bled and karyotyped by leucocyte culture. Twelve were found to be sex-chromosome chimeras of which five were single-born. Three out of the five singleton sex-chromosome chimeric heifers were slaughtered and at post mortem examination abnormalities of the reproductive tract were observed. Two the the slaughtered animals were Friesian heifers that had shown normal oestrous cycles and had reproductive organs apparently normal on clinical examination; however, one of them with 5 per cent male cells had a nonpatent cervix, while the other with 12 per cent male cells had non-patent uterine horns. Both heifers possessed functional ovaries, the former had an active corpus luteum and the latter had a developing follicle. The third heifer with 45 per cent male cells had a normal vagina, enlarged clitoris, seminal vesicles and gonads resembling fetal testes with both primitive ovarian and testicular structures. The Old Gloucester and Friesian heifers with 2-5 per cent and 12-0 per cent male cells are alive and have normal external genitalia but rudimentary uterine horns with no palpable gonads. Cytogenetic examination has demonstrated for the first time the existence of single-born freemartins resulting from the death of their male co-twins after fetal vascular anastomosis has been established.