Hiya,
We have great fun stopping my cats eating the dog food as they seem to love it, but it does give them very upset stomachs, and so the vet advised us not to let them eat it.
We first thought they had a stomach bug, so took Splodge to the vets as he was the worst, and they asked if they could of been getting hold of the dog food, and we said yes, they had! We stopped this, and soon after we had no more problems!
Dont know if this was just our cats, or the food we feed the dogs! But we keep the cats well away now.