MerrickPurrfect Bistro Parfait Chicken & Tuna Cat Treats

The most common protein in pet food, and for dogs one of the most common food allergens, with beef and dairy. If chicken is what your pet reacts to, it hides everywhere: chicken fat, chicken broth, chicken meal, natural flavor. On a label, chicken listed first is weighed with its water still in, so a food leading with fresh chicken often has less chicken protein than one leading with chicken meal. Neither is better; they are different measures.

A complete, highly digestible protein, which is why formulators like it. It is also a documented allergen in about 4% of dogs with food reactions. Egg allergy does not implicate chicken meat; the proteins are different. Dried egg product is the same thing with the water removed. A good ingredient for most pets and a fine-print one for the allergic few.

A fish used mostly in cat foods, where its strong flavor is the point. Tuna is a good protein and a source of omega-3 fats. Two cautions apply to tuna fed often: it is higher in mercury than smaller fish, and cats can become fixated on it and refuse other foods. Both cautions apply to the cat eating tuna every day, and much less to tuna as one ingredient in a complete food fed in rotation.

Starch from the cassava root, used to bind kibble and as a carbohydrate source, especially in grain-free foods. It is nearly pure starch with little protein, fiber or micronutrients, and it is one of the least likely ingredients to trigger an allergy. A food that leans on tapioca for carbohydrate is getting easy digestibility and little else from it, which is fine as long as the rest of the recipe carries the nutrition.

The dried cells of yeast, often a by-product of brewing. It is rich in B vitamins, protein and minerals, improves flavor, and contains compounds that may support gut bacteria. Despite a persistent myth, there is no evidence it repels fleas. Yeast is an uncommon allergen in pets. Yeast culture is a slightly different product, a fermented feed that supplies similar nutrients.