Nowadays it’s so common, there’s probably a foley artist specialist “Barking Spiders, Inc. of Culver City, CA,” But there was a time within living memory that the embargo upon the fundamental sigh was strictly observed - even without a specific note in the Hayes code.
Pre-Blazing Saddles all I can recall in this respect is that scene in “The King And I” when the little princelings were being introduced to Anna, but even then it was simply implied. Even accounting such obviously gastrically afflicted actors as W.C. Fields and Wallace Berry, I can’t remember any old movies that included “singing the Irish National Anthem.”
One of the Pink Panther movies had such a scene. Inspector Clouseau is in disguise as a Mafia don, and is on an elevator with several thugs. Clouseau expels, and the scene progresses from there.
Well, there’s a scene in “The African Queen” which works better if you assume the sounds coming from Bogart are farts, but they are meant to be his stomach growling, I guess.
I seriously doubt the Hays office would have allowed the real thing, however.
That Pink Panther movie came after Blazing Saddles.
In that scene from The King and I, it was not implied that the little princess broke wind. Instead of continuing to face Anna and backing away from her like everyone else, she turned around. Turning your back to someone in a situation like that is a huge social faux pau.