Question

Free-martin is

• A. Sterile female calf born co-twin with male calf
• B. Sterile male calf born co-twin with female calf
• C. Sterile female calf born co-twin with female calf
• D. Filly born out of mating between mare and jack

Hint:

Over 90% of female calves born co-twin with a male calf are freemartins.
This condition can be diagnosed early using a simple vaginal length probe or PCR test for Y-chromosome chimerism.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Freemartinism is a form of intersexuality that occurs in cattle and occasionally other ruminant species.
It is caused by the sharing of placental blood vessels between male and female fetuses during a twin pregnancy.

Step 2: Detailed Explanation:
When a cow is pregnant with male-female twins, the chorionic blood vessels of the two fetuses often fuse during early gestation.
This fusion allows blood containing hormones and cells to mix between the developing fetuses.
Anti-Müllerian Hormone (AMH) and testosterone produced by the earlier-developing male fetus enter the female's circulation.
These male hormones suppress the development of the female reproductive tract (Müllerian ducts) and stimulate some male characteristics.
As a result, the female calf is born with an underdeveloped, non-functional reproductive tract and is sterile.
This sterile female calf is called a "freemartin."
The male twin is typically fertile and unaffected.
Twinning with another female does not cause freemartinism because no male hormones are present.

Step 3: Final Answer:
A freemartin is a sterile female calf born co-twin with a male calf.