Freemartinism

Todayโ€™s path rounds are on ๐Ÿ๐ซ๐ž๐ž๐ฆ๐š๐ซ๐ญ๐ข๐ง๐ข๐ฌ๐ฆ! This is kind of a wacky thing that happens in cattle.

๐–๐ก๐š๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐…๐ซ๐ž๐ž๐ฆ๐š๐ซ๐ญ๐ข๐ง๐ข๐ฌ๐ฆ is an abnormality of sexual development, where a female calf is born with ๐œ๐ก๐ข๐ฆ๐ž๐ซ๐ข๐ฌ๐ฆ (having two complete genome sets in the body) with some cells having XX sex chromosomes and some cells having XY chromosomes.

๐–๐ก๐จ ๐ ๐ž๐ญ๐ฌ ๐ข๐ญ?
This condition is most commonly found in cattle, and occurs when there are twins, with one being female and one being male. Under these circumstances, up to 90% of the female calves born will be freemartins. The male twin is almost always completely unaffected.

๐–๐ก๐š๐ญ ๐œ๐š๐ฎ๐ฌ๐ž๐ฌ ๐ข๐ญ?
During development of the twins, an ๐š๐ง๐š๐ฌ๐ญ๐š๐ฆ๐จ๐ฌ๐ข๐ฌ (a connection between two vessels) develops between the placentas of the two calves. Once this happens, blood is exchanged between the two twins. The male twin produces ๐ญ๐ž๐ฌ๐ญ๐ข๐ฌ-๐๐ž๐ญ๐ž๐ซ๐ฆ๐ข๐ง๐ข๐ง๐  ๐Ÿ๐š๐œ๐ญ๐จ๐ซ๐ฌ, which are hormones that stimulate the fetal ๐ ๐จ๐ง๐š๐ (primal testicle or ovary) to develop into testicles instead of ovaries. These hormones get passed to the female calf through the anastomosis, and inhibit her gonad from developing into an ovary.

๐–๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐š ๐ฉ๐ซ๐จ๐›๐ฅ๐ž๐ฆ?
Without having proper stimulus to develop the female reproductive system, the freemartin calf will have extremely small and thin uterine horns. Their โ€œovarianโ€ tissue may also be partially or completely differentiated into testicular tissue. Because of these two factors, a freemartin will not come into heat, and in most cases cannot get pregnant. Sometimes, depending on the amount of testosterone produced by their โ€œtesticlesโ€, they can also display bull-like behaviour and become dangerous. Therefore, these cattle are usually culled from breeding operations and sent to feedlots to be finished for the meat industry.

๐๐ก๐จ๐ญ๐จ๐ฌ
1-2) Examples of twins showing the anastamosis between the two calves.
3-4) Examples of poorly developed reproductive tracts from freemartins.
5) An example where the ovaries have developed into testicles, but a uterus is still present! Weird.

๐’๐จ๐ฎ๐ซ๐œ๐ž๐ฌ
Maxie, G. Jubb, Kennedy and Palmerโ€™s Pathology of Domestic Animals, Volume 3. Sixth Edition.

Photos 1-5 courtesy of Noahโ€™s Arkive.

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