One of the biggest questions we get asked is what is the best way to transition a pet between foods.
The accepted procedure is to wean the pet between the foods over a week by mixing the foods, gradually moving from one to the other. 25% new, 75% old for a few days, 50/50 for a few days, 75% new, 25% old for a few days and you're done. This works where the type of food is the same, just the brand/quality is changing. Dry to dry, canned to canned or raw to raw. Changing modality of foods (dry to raw) is a whole different discussion.
Generally, when improving the quality of the food, transitioning is less important. Dropping a level is much more of a concern. If you forget your high quality kibble at home when you go to the cottage, and pick up something from the grocery store, the output will probably be pretty nasty, and not a pleasant ride home.
Cats seem to have less of a digestive issue in transitioning, but getting them to eat a new food can sometimes be a challenge. Little dogs too. Medium and large dogs can be "starved" into eating a new food, they have the ability to fast without an issue. With small dogs and especially cats, we don't want to do this with. If they go without food too long, it can cause very severe health issues.
As the cute saying goes, "Dogs have owners, cats have staff". With the little ones, we have to find a way to entice them to eat. Depending on the type of food you use, this can be a task. Dry to dry, you can try changing the flavour of the kibble, or add in something the cat finds irresistible, like the liquid from sardine/tuna/salmon (no added salt). Sometimes some low sodium broth, warmed up, will work. Or something like freeze dried liver sprinkles, or even a tiny bit of parmesan cheese.
Can to can, try placing both flavours side by side in the dish. The animal will eat its favourite, and when it is still hungry, may eventually eat the new product. Sometimes mixing the two up, with 75% the favourite, and 25% the new flavour can introduce the new one without a hunger strike. Whatever happens, though, make sure that the animal is consuming some food.
Moving up in quality can make noticeable changes in the animal. Notice I said quality, not price. There are well advertised foods out there you might think are higher quality, but by reading the label, you will see they may not be what you thought. Meat first is important, but more meat is more important. Quality of meat is also a big factor, when they use the generic term meat meal or meat by products, it is a lot lower quality ingredient than a specific type of meat, like chicken or lamb.
Better quality foods mean better nutrition. It's pretty simple, really. There isn't a pet food marketed that is not capable of meeting a normally healthy pets basic nutrition needs, but we don't just want to keep the animal alive, we want them to thrive. Better foods mean better health, for people or animals. Buying better food can save on health issues and actually be cheaper in the long run. Plus, the animal will live a longer, happier and healthier life.
Pets have a job to do, they make our lives better. Let's make their lives better right back.