In fiction mobsters often use slaughterhouses to cover up their own dirty business. Do we know of any historic cases where slaughterhouses were used to make people 'disappear'?

I can think of at least one case where a mobster was killed in a slaughterhouse. William 'Action' Jackson was suspected of being a police informant, so his associates (among them the infamous 'Mad Sam' de Stefano) took him to a meat rendering plant on the south side of Chicago, hung him up on a meat hook and tortured him to death.

Additionally, Angelo LaPietra acquired the nickname 'the hook' for hanging his victims on meat hooks.

https://abc7chicago.com/archive/7411822/

I can't really tell you if mobsters making people disappear this way was a common occurrence, due to the fact that if it did happen obviously most victims, well, disappeared.