Can't say I've ever had much to do with Pyranees mountain dogs, Pam. Closest I've come is working with St Bernards. Now they do fart, but I don't remember much burping - maybe a bit of bicarb in his water bowl would help?
I think we've hit on something here, SoccerMom. Thinking about it, where I used to live, the nannies did fart, but the boys definitely didn't (talking about wethers not billies here).
I cite in evidence, young Bob. Located to your left on the screen. He is the one lazing on a sofa. Never a fart I have heard and we have lived in close proximity for long periods.
I don't know whether it's their diet or internal construction, or a combination of both. The boys tend to get a lot less concentrate than the nannies because they don't need it for milk production.
Mind you, if I ever do hear him fart, y'all will be the first to know