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Faunsdale, AL | Actually it's a bit more complicated than that..............At least it was 30 years ago when I learned it!
An early fetal calf is either a male or female genetically, but has the beginning of both male and female reproductive tracts until the male is selected by release of mullerian inhibiting substance. MIS causes the regression of the female tract and the calf develops the male parts. If no mullerian inhibiting substance is released, then the calf becomes a female and the male tract never develops. I occasionally see "gartners ducts" which look sort of like a penis and protrude from the vaginal opening of some cows especially when in heat and being AI'ed. These are remnant of the male ducts (probably ampulla) which developed a little and are attached to the side of the vagina/vestibule of the affected cows. These cows seem to be perfectly fertile, so In my book it is just one of those things that you see occasionally.
A female twin with a male gets a dose of MIS because they almost always share blood with their twin through interconnections of the two placentas. One of the tests for freemartins in very young calves is to test for male chromosomes in the heifer's blood. Pretty easy to do in this age of genomics. However, most of them can be picked up by just looking closely. They tend to have VERY small teats when other heifers just have small teats. They also typically have fewer, but longer and coarser hairs on their vulva as well as a very shallow/undeveloped vagina. Once they're old enough to palpate, the reproductive tract is tiny if it can be felt at all. | |
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Question about question about triplets from below.
