Its real simple to pick out dog or cat food.
READ the label.
Buy foods with NAMED meat sources. Never ever pay any attention to the pretty food labels on the cans and bags. Read the ingredient list, its the only place where they legally have to tell the truth.
Ex. Chicken, Chicken Liver, Chicken Meal. (this is good, named meat sources, no corn)
Do NOT buy food labeled Chicken, Liver, Meat Meal (this is bad, the liver and meat meal do not say what animal it comes from)
if it doesnt name the type of animal it is from, it is low quality garbage.
Do not buy food with Pea Protein, any type of corn, any type of animal byproducts/ if it has corn in it, you are really at the bottom of the barrel in food quality. Animal byproducts can be anything, think about it.
Do simply google cat food (or dog food) ratings. You will learn a lot.
NEVER EVER feed your dog or cat one brand of food!
Do you think you would live a long healthy life if you ate Burger King every day of your life?
Same goes for pet food. Feed at least two different brands of food, we feed around 6 different brands of quality food, we also feed left over table food. Canned food is much more healthy then dry but if, because of cost you have to feed dry, still all the above applies.
No corn, no by products, ONLY named animal meats, also watch fat content as much as possible. Use at least two different brands of food per week, 3 is much better.
Even though this is a dog food link, you can find the same for cat food but its a good read because it applies just the same.
https://www.dogfoodadvisor.com/dog-food-reviews/rating/
https://catfooddb.com
There are MANY sources available on line and in the press, again, never feed the same food every day. Vary by two three, four different companies every week. Cheap garbage dog and cat food cause endless health issues for animals. Much the same for humans.
Most Vets do not know anything about pet food.
"Overall, with 50 varieties reviewed producing an average score of 3.7 / 10 paws, Hill's Prescription Diet is a significantly below average overall cat food brand when compared to all others brands in our database" (from the link I posted above, my god, just read the cheap ingredients)
Having a pet is great and rewarding, it is also heart breaking when one is ill for some unknown reason.
I would be willing to bet 60% or more pet issues are caused by the garbage pets are eating. Unknown to the pet owner, trusting the manufacturer instead of reading the labels plus use common sense, why one earth (once you think about it) do people feed pets one food brand for the animals life? Do people eat the same exact food and brand every day of their life, trusting their health to a corporation? ha
Start today, vary food brands, read the labels, get the corn, meat by products out of their diet, feed food with ONLY meat based protein.
Im willing to be in a matter or weeks, most owners would see a more healthy pet after they cut out the Purina type mainstream garbage.
Much like a human who would cut out fast food.
If possible, wet food, but dry ok or a mix of the two.