I had the same problem with my catahoula and I've tried blue buffalo a couple times over 2 years. Everytime I switch to Blue he gets terrible gas, paint peeling, nostril burning gas. I only switch food a couple times a year and the gas persists while he is eating it.

I now feed Ancana or Encana (sp?) and I really like it. Quality food, little pricey admitted, but he looks great, keeping his weight on and stool quality is great.