This archive report was first published on 5 October 2019.
On a typical farm, twin calves are often seen as a blessing, but in some cases, they can be a curse. In this article, we will explore the rare condition of freemartinism, where a female calf born as a twin with a male is often sterile.
According to Dr. Joseph Mugachia, a veterinarian who encountered this condition on a farm, freemartinism occurs in 90-97 percent of cases where a female calf is born as a twin with a male. The condition is caused by the sharing of blood vessels in the placenta between the twins, resulting in the mixing of male and female hormones in the foetuses.
As a result, the female hormones are unable to control the development of the reproductive organs in the female calf, and the male hormones override the process. This leads to the development of external feminine deformities in the vulva, including a tuft of hair and increased muscular development of the heifer calf, making it appear like a bull.
But that's not all. The disruption caused by the male hormones is permanent, and the heifer calf is unable to function as a female. The uterus fails to develop, and the ovaries may fail to develop or develop with testicular and ovarian tissues, making them non-functional. The oviducts, or fallopian tubes, may develop poorly or be absent, and there is no continuity of the reproductive tract from the vulva to the ovaries.
Dr. Mugachia attributes the case of freemartinism on the farm to the use of hormones to induce heat in cows. Since the farm started using hormones about four years ago, twinning has increased, and this was the first freemartin case. However, six other cows were bred through hormone treatment early this year, and the farm can only hope they will not surprise them with more freemartins.
Freemartinism is diagnosed by the history of bull-heifer twin births and confirmed by the tuft of hair on the vulva and increased muscular development of the heifer calf. DNA tests are available but are not commonly used due to high costs, low availability, and the fact that it is almost certain a heifer born with a bull as twins will be sterile.
Freemartins are usually treated like bull calves, depending on the practices of the dairy farm. In this case, the farm manager, Njoroge, decided to rear the heifer to maturity with the bull calves for learning experience. Dr. Mugachia will be following this case, hoping to find out the state of disruption of the reproduction system when the freemartin is finally slaughtered.
