There are a few ways vets do it now apparently. One I heard that they can actually replace them with prosthetic ones. They used to take the skin and everything but now they seem to leave the skin which can from my understanding have a regrowth of fatty tissue inside which has nothing to do with hormones. I know that the vet told me that it takes up to 6 weeks for the hormones to settle down in an adult animal that has been desexed.