Just a thought here about the 6 months testing on dog food - would it interest you to know that when breast implants were implanted into dogs for testing, they also only had to show how the dogs were doing at the 6 month time period, after which many died.
The testing up to the 6 months was the only thing that was public knowledge, not after that!!! So many laymen thought they were safe... when in deed they are very poisonous and have caused many women a myriad of health problems and many have died.
My point here is that 6 months is surely too short a period of time to show whether a dog food is safe IMHO.