BillinDetroit writes:

cross-breeding,

As shown below, the prohibition was against interbreeding "of two
sorts". That is, no matching up a camel with a bull, a chicken with a
goose and so on. To the best of my knowledge, only horses and asses
can breed like that and produce offspring, but even then, the
offspring (a mule) is sterile.
etc.

Wolves and dogs crossbreed.
liger - lion and tiger