Bechorot 6 - Mutants
Following rulings discuss the laws of mutants (known as "one that resembles something else") - first, as they apply to firstborn, and then as they apply to kosher and non-kosher animals.
If a cow bore a firstborn resembling a donkey, or a donkey bore a firstborn resembling a horse, it is exempt from the laws of firstborn. The Torah said, " Firstborn of a donkey ," and then repeated, " Firstborn of a donkey " to tell us that the offspring must resemble his mother, a donkey.
What is the status of such an animal for consumption, for example, if a cow bore a calf that resembles a donkey? If a kosher animal bore an offspring resembling a non-kosher animal, it is still permitted for consumption, even if it is lacking kosher signs. Conversely, if a non-kosher animal bore an offspring resembling a kosher animal, it is forbidden for consumption. Here is the rule: a product of that which is non-kosher is itself non-kosher, and the product of that which is kosher is itself kosher.
Art: Karel Dujardin - A White Horse, A Cow And A Donkey In A Landscape