The Biology:
* Shared Placenta: Cattle twins often share a placenta. This means their bloodstreams are connected, allowing the exchange of blood cells and hormones.
* Hormonal Influence: The male calf's testes produce testosterone, which enters the female calf's bloodstream. This exposure to high levels of testosterone during development disrupts the female calf's reproductive system.
The Consequences:
* Infertility: Freemartins are almost always infertile. Their ovaries are underdeveloped, often missing or rudimentary. They may have a small, undeveloped uterus and external genitalia that may appear normal.
* Physical Appearance: Freemartins generally look like normal heifers but may have some physical traits that are more masculine, such as a larger frame or a straighter tail.
Why it Matters:
* Breeding Programs: Identifying freemartins is important in cattle breeding programs to prevent the waste of resources and time attempting to breed them.
* Economic Impact: Freemartins cannot produce calves, impacting the profitability of a cattle operation.
How to Detect Freemartins:
* Examination: Veterinarians can examine the reproductive organs to determine if the female calf has a fully developed uterus and ovaries.
* Blood Tests: Blood tests can detect the presence of male hormones (androgen) in the female calf's bloodstream.
* Genetic Testing: Genetic testing can confirm the presence of the male Y chromosome, which is usually found only in males.
In summary: Freemartins are infertile female calves born twin to a male due to the sharing of a placenta and the resulting hormonal exposure. Identifying them is crucial for effective cattle breeding and management practices.