Vasectomy: In a more delicate procedure than castration, the vasa deferentia – ducts that run from the testes to the penis – are cut then tied or sealed, to prevent sperm from entering into the urethra. Failure rates are insignificantly small. Breeders routinely have this procedure carried out on male ferrets and sheep to manipulate the estrus cycles of in-contact females. It is uncommon in other animal species. Because a vasectomy is usually a more expensive procedure, among pet-keepers it is more often performed on show animals, to cosmetically preserve their appearance (though depending upon the fancier organization, the procedure may invalidate the animal's candidacy for certain awards, or relegate it to a non-pedigree, generic "household pet" competition division, just as with full castration).