The suggestion from your Vet applies more to cats that are being switched from one plant rich diet to another. It usually takes about ten days for the cat’s digestive tract to grow a new set of gut bacteria to help process the new plant products. Our ZERO foods do not contain plant products so the adjustment period will not be the same. Animal proteins and fats are, for the most part, digested enzymatically by your cat and gut bacteria plays a much smaller role in the digestion of a truly carnivore food. Think of it this way; if a cat consumed a mouse one day and a lizard the next would that cat have diarrhea from the change in diet?
Soft stool the consistency of mashed potatoes does occasionally happen when you feed our food. The soft stool is not caused by the changeover to the carnivore diet, but by the fact that the cat needs to learn to eat less of our nutrient-rich carnivore food. Most cats learn this within 1-3 days and a few may take as long as two weeks. If you mix our food with their existing food then the carbs in the old food will likely cause the cat to overeat both foods and your cat will quickly gain weight and likely still have soft stool.
A second concern with the gradual change over is many cats do not accept change well. They will eat the new food mixed with the old for a few days. Eating both foods may cause them to feel stuffed, they blame the new food and revert back to eating only the old food. Sometimes the flavor of the new food will entice them to try it, and again in a few days they think that they may have acted rashly and revert back to eating the old familiar food, because it is the safe choice.
We have found the best choice is to switch the cats cold turkey and monitor every cat to make sure they are eating. Most ten pound cats will consume about 45-60g a day of the standard high carb food and that same cat will usually only consume about 35g of our food. Overeating should quickly resolve, unless the overeating is due to competition. Cats do not share well when it comes to food. If they feel that there is competition for their food they will overeat. If they see a bowl less than half full or an aggressive cat is glaring at them when they try to eat, they will overeat. Feeding free choice with one bowl for every cat in the house, putting each bowl in a different room of the house and keeping all bowls more than half full will prevent overeating for all but a few cats. The back label of the bag will explain our feeding method in great detail.