Why bother neutering mountain gnomes? Just kill them; they're useless.
Gnome mercy
I think female sterilization would be beyond the scope of dwarven civs, we don't even have the ability for animal caretakers to actually do veterinary care, much less a tubal litigation or removal of the ovaries entirely. That's a hardcore surgical procedure. Whereas gelding is basically crushing the top of the scrotum pouch so tightly the entire scrotum can be removed.
It's quite brutal. I've watched my share of videos espousing the evils of animals kept for meat production. Regardless of if you are okay with it or not, it is very unpleasant to watch. (unless you've done it a lot yourself, then it sort of becomes business as usual, I'm sure.)
Gelding doesn't need increased animal aggression, herd animals have to be micromanaged enough. I would use gelding liberally to get the best possible stock for meat production and to make sure beloved pets don't impregnate my milking pigs (and animals will produce milk without having been pregnant or having a male in the vicinity from what I can tell. I usually just bring a couple sows with me, no need for a grazing spot and they can be milked.)
I'm very excited about this addition.
As for mountain gnomes, you can breed them for meat production. Therefore, you'd want to geld the gnomes that are the least... gnomey? So that you could breed a superior stock of mountain gnomes for their delicious gnomey meat products.