Why Is A Female Calf Infertile If It Is Born A Twin Alongside A Male Calf?

19 December 2017, 16:19

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Mystery Hour Question

If a cow gives birth to male and female twins, the female calf will never be able to breed. If it’s two males, no problem. If it’s two females, no problem. But if she gives birth to a male and a female, the female calf is infertile. Why is that?

Felix, Luton

Answer ** Definitive **

Name: Ben, Twickenham

Qualification: Biology teacher

Answer: When a heifer has twins, the placenta membranes will often merge in the uterus. As a result, the blood vessels from each of the calves get really close and start to share antigens and proteins. This means that the calves start to develop some of the characteristics of the other gender, rendering the female twin interfile and reducing the fertility of the male calf.