I'd agree with the OP on that diet. For years I fed only Vet purchased food- eg, Eukunaba/iams, and others and the last big male dog I had developed all manner of aggressive cancers that would pop right back the minute they were surgically excised. The dogs I had prior to that were farm raised and ate raw meat and never had the cancers we see today. I'm convinced that the cancers we see are related to commercial pet foods and while the vets are given preferential access by the pet food companies to sell the food either on discounts or commission (Why can't one buy this in supermarkets???) they are
NOT qualified in pet nutrition and all pet nutrition research is sponsored by the pet food companies. surprise surprise.
There's a local company that makes excellent dog pellets and more importantly, affordable, unlike the imported foods. Montego Classic is the name but I've recently found that there's no consistency in the product. Some months the dogs like the food other months the dogs won't. This stuff is made fresh and it's well priced but now I'm steering back to feeding the dogs dirty tripe which I buy prepacked and frozen in meal size portions of 1kg. Thing about tripe is that it's a fatty food and gives their coat real gloss. The downside is dirty tripe smells like week old corpses left in the sun, so it's advisable to thaw the stuff early in the morning for an evening feed