I think there's been a mix up in communication somewhere

Mangalitzas were/are a lard pig, you
can get huge amounts of fat from them - up to 70 litres from one carcass apparently
BUT you'd have to be feeding them on double cream and lots of fatty food stuffs.
If they've been fed a sensible balanced diet and not rushed to finishing weight there's no reason why they should be any fatter than any other traditional breed (and OSB's a generally a leaner breed anyway so having that in the breeding is a good thing

)
A good butcher will separate the fat from the meat and mix it at an appropriate level for sausages (normally around 80% meat to 20% fat) any excess fat would be discarded (or in my case, brought home, turned into lard and then into soap

)
I'd send it off and just make sure the butcher knows you don't want overly fatty sausages.
HTH
Karen