Mule Sterility |
Why are mules and hinnies sterile?
Mules and hinnies are crossbred between 2 species: donkeys which have 62
chromosomes and horses which have 64 chromosomes. Donkey and horse
chromosomes also differ slightly in structure. Mules and hinnies have 63
chromosomes that are a mixture of one from each parent. This prevents the
chromosomes from pairing up properly and creating successful
embryos. While this is generally true, there are a few reports of fertile
mules and hinnies.
Laura Hungerford, DVM, MPH, PhD
University of Nebraska
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Update: June 2012