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What is a freemartin in cattle?
When a cow is pregnant with multiple offspring (twins or more) there is movement of hormones between them, particularly if they share the same placenta. In the case where …there is a male fetus and a female fetus, the hormones (testosterone) produced by the male can negatively affect development of the female reproductive organs causing her to be born sterile, in which case the reproductive organs of the female are underdeveloped and/or she also displays male reproductive organs. The sterile female calf is thus called a 'freemartin'. This is one reason why it is undesirable for cows to carry multiple offspring and why farmers do not encourage or select for this condition. (MORE)