– Steve Boyles and Mike Day, The Ohio State University Animal Sciences
At the recent Ohio Beef Expo a producer came up to me and asked about freemartins. He had a good cow that had twins. One of the calves was a bull and the other was a heifer. The producer wanted to know if he should keep the heifer and try to breed her.
Freemartinism, which occurs primarily in cattle, is the sexual modificaton of a female twin by in utero (meaning in the uterus) exchange of blood from a male fetus. It has been assumed that the exchange of blood occurs due to fusing of the placenta between the two fetuses. While sheep, goats, and pigs can have multiple births, rarely is there an exchange of blood between fetuses. Freemartins are characterized by:
- 1. Internal reproductive organ of both sexes
- 2. Modified ovaries with varying degrees of similarity with male testicles
- 3. External genetalia that resemble those of a normal female in many cases.
- 4. Blood chimerism (blood group and sex chromosome, XX/XY)
A true freemartin will not exhibit estrus and is sterile. As previously stated, the external genitalia may appear normal but lead into a much shorter vagina and a rudimentary uterus. Frequently the clitoris is enlarged. The teats are shorter than those in 3- or 4-month-old normal heifers
Betting that a heifer born with a bull is “normal” is a bad bet. Only 6 to 8 percent of the time is the female reproductively normal. A relatively simple test for freemartinism in newborn heifers is to insert an instrument into the vagina and measure the depth of the vagina. In normal heifers, the instrument can be inserted into the vagina approximately 5 inches, whereas in a freemartin, depth of the vagina is usually only around 2 inches. A test tube that is 5 to 6 inches in length can be used for this purpose. A person experienced in rectal palpation of the reproductive tract can determine the presence, or lack thereof, of a complete tract at approximately 1 year of age in suspect heifers. You can work with your local veterinarian to attempt to determine if your heifer is one of the few that are not detrimentally affected by being born with a bull calf. The bull calf of this pair is fertile although it has been suggested that he might have a slightly lower sperm count than would a normal bull.