Not Medical Advice: The dog might be suffering from gastrointestinal upset.
When excess gas forms in the stomach or intestine, it eventually has to be released through one end of the gastrointestinal tract or the other. The clinical signs of gas in dogs depend largely upon which end of the dog the gas is released from.
Owners of dogs with gastrointestinal gas usually notice one or more of the following symptoms:
Audible passage of gas from the anūs (with or without odor)
Rumbling sounds coming from the abdomen (“borborygmus”)
Abdominal discomfort (usually mild)
Burping (belching; eructation)
A feces-like smell near their dog
Vomiting, diarrhea, weight loss, lack of appetite (may be present if flatulence is caused by underlying gastrointestinal disease)
As per Petwave.com, most natural gastrointestinal gas in dogs is odorless. The small amount that passes with a foul smell usually contains ammonia, indole, skatole, volatile amines, hydrogen sulfide and/or short-chain fatty acids. It can be caused by ingestion of cruciferous vegetables, onions, high-protein diets, endogenous mucin and bile acids.
Check out some tips on how to cure your dog’s upset stomach at Caninejournal.com.