I suppose if I spoke American more, I, personally, would probably say 'spayed' or 'neutered.'
Every German vet I know calls the procedure a 'castration,' whether a male or female (but with German spelling and accent).
Apparently Germans have no good euphemism, because when I talk with my Germans, they call it a 'snip-snip,' complete with awkward pause and hand-scissor motion.
SO! Where are you from, what do you call it, is it gender-specific, and is it a euphemism?