Is sex with animals wrong?

Yes, sex with animals is wrong. God forbids this sexual perversion known as bestiality. This is what He says in His word.

Ex. 22:19, "Whoever lies with an animal shall surely be put to death."
Lev. 18:23, "Also you shall not have intercourse with any animal to be defiled with it, nor shall any woman stand before an animal to mate with it; it is a perversion."
Lev. 20:16, "If there is a woman who approaches any animal to mate with it, you shall kill the woman and the animal; they shall surely be put to death. Their bloodguiltiness is upon them."
Deut. 27:21, "Cursed is he who lies with any animal. And all the people shall say, 'Amen.'"

Clearly, this sin is forbidden by God since it violates the natural created order of sexual union between a husband and wife.