I work in animal nutrition, and have since 2003 (I used to work for a vet, now I work at an independent pet food store - mostly holistic).
What I urge people to do most, when feeding their pets, is to do their research. Read labels. Look up anything you don't recognize. I used to feed my dog Nutro Lamb & Rice, and her skin and coat were pretty good, she was in okay health, but she was getting chubby because we used to spoil her rotten.
My vet recommended I feed my dog Hill's Prescription Diet W/D for her weight and Hill's Prescription Diet T/D for her teeth. I did this diligently for a year.
Her coat turned to crap, she was lethargic, worn out...
And then I read the labels.
T/D contains: Calcium sulfate, better known as gypsum, Plaster of Paris, or DRYWALL. Potassium chloride, which is a "salt substitute" that may cause nausea, vomiting, diarrhea, and bleeding in the intestines. Overdoses may cause cardic blocks and other heart problems... not smart for a dog with a heart problem to begin with!
W/D contains: Peanut hulls! And something mysteriously labelled "digest".
My vet wanted me to feed my dog peanut shells, drywall, and something that might mess up her heart. Not to mention the "chicken by-products", which is organs, bones, heads, feet, and FEATHERS.
Why do so many vets recommend these foods? Because the companies pay them to. The big offenders are Hill's (Science Diet, Prescription Diet), Royal Canin, Eukanuba/Iams, and Purina.
I feed my dog a holistic food now (Nutro
Ultra Senior). I can identify everything on the label. Her coat has never been better, her joints are in great shape since I've bought the one with added glucosamine (she has arthritis). She's still energetic and healthy at the ripe old age of ten.
Canned food is a treat, or for elderly/sick dogs, as far as I've seen. Healthy dogs don't NEED it in their diet, unless they have kidney problems.
I'd recommend holistic and natural. We tried Ginger on Eagle Pack Holistic Select, but it did funny things to her tummy (she's a little sensitive). I recommend Eagle Pack, Nutro (especially Ultra), Merrick, Fromm, and Wellness as my top picks, because I've seen the results in a number of animals.