BobY wrote : they ought to be saying they are going to spade their bitch

Well, yes and no.
The might want to say they are going to have the dog spayed and the listener could deduce the animal was a bitch.
On no account is spaded or spade the correct term whether you use dog or cat or whatever for a female animal.
Of course you could get past it by saying your having the Vet do a hysterectomy on your animal.
Is there a male equivalent to hysterectomy? I know men who are somewhat hysterical and even a few given to fits of hysteria!
wow