Todayโs path rounds are on ๐๐ซ๐๐๐ฆ๐๐ซ๐ญ๐ข๐ง๐ข๐ฌ๐ฆ! This is kind of a wacky thing that happens in cattle.
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐
๐ซ๐๐๐ฆ๐๐ซ๐ญ๐ข๐ง๐ข๐ฌ๐ฆ is an abnormality of sexual development, where a female calf is born with ๐๐ก๐ข๐ฆ๐๐ซ๐ข๐ฌ๐ฆ (having two complete genome sets in the body) with some cells having XX sex chromosomes and some cells having XY chromosomes.
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
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.
๐๐ก๐๐ญ ๐๐๐ฎ๐ฌ๐๐ฌ ๐ข๐ญ?
During development of the twins, an ๐๐ง๐๐ฌ๐ญ๐๐ฆ๐จ๐ฌ๐ข๐ฌ (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 ๐ญ๐๐ฌ๐ญ๐ข๐ฌ-๐๐๐ญ๐๐ซ๐ฆ๐ข๐ง๐ข๐ง๐ ๐๐๐๐ญ๐จ๐ซ๐ฌ, which are hormones that stimulate the fetal ๐ ๐จ๐ง๐๐ (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.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
Without having proper stimulus to develop the female reproductive system, the freemartin calf will have extremely small and thin uterine horns. Their โovarianโ 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 โtesticlesโ, 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.
๐๐ก๐จ๐ญ๐จ๐ฌ
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.
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Maxie, G. Jubb, Kennedy and Palmerโs Pathology of Domestic Animals, Volume 3. Sixth Edition.
Photos 1-5 courtesy of Noahโs Arkive.
