The scores
Instinct Original Kitten: A (90/100)
Instinct Original Cat: B (78/100)
A 12-point gap is one of the largest we’ve seen between a kitten formula and its adult counterpart from the same brand. The kitten version jumps an entire letter grade — from B into A territory — which puts it alongside Orijen and Acana at the top of our cat food rankings. The adult formula is still a solid B, but the kitten version is genuinely premium in a way the adult formula isn’t.
How the ingredients compare
Here are the first five ingredients side by side:
Instinct Kitten: Chicken, Turkey Meal, Menhaden Fish Meal, Peas, Chicken Fat
Instinct Original Cat: Chicken, Chicken Meal, Turkey Meal, Peas, Chicken Fat
Both formulas lead with chicken and share a similar structure — animal protein first, followed by meals and peas. But the kitten version swaps out one of the redundant chicken sources for menhaden fish meal, immediately adding a different protein species to the top five. Beyond the top five, the gap widens further: the kitten formula adds egg product, white fish meal, and lamb meal deeper in the ingredient list, reaching 6 distinct animal protein sources. The adult version stays with chicken, chicken meal, and turkey meal as its only animal proteins — just 3 sources total.
Where Instinct Kitten pulls ahead
Double the protein sources. The kitten formula includes chicken, turkey meal, menhaden fish meal, egg product, white fish meal, and lamb meal — 6 named animal protein sources from 5 different species. The adult version relies on chicken, chicken meal, and turkey meal — 3 sources from just 2 species. For growing kittens that need a complete amino acid profile, this diversity matters. But it’s not just a kitten benefit — wider protein variety is better for any cat’s nutrition.
Menhaden fish meal. This is a whole-fish meal from a small, oily fish that’s one of the best natural sources of DHA and EPA omega-3 fatty acids. It appears in the kitten formula’s top three ingredients, delivering marine-sourced omega-3s from the protein foundation itself rather than from supplemental oils alone. The adult formula has no comparable fish ingredient this high in the list.
Higher overall ingredient quality. A 12-point gap doesn’t come from one or two differences — it reflects a formula that was built to a higher standard across the board. The kitten version’s broader protein base, additional animal-source ingredients, and more complete amino acid profile add up to a meaningfully better food. The jump from B/78 to A/90 moves this formula from “good” to “top-tier.” Shop on Amazon →
Where Instinct Original holds its own
Designed for adult maintenance. The adult formula’s lower protein concentration and simpler ingredient profile is intentional — adult cats in maintenance mode don’t need the same protein density as growing kittens. For less active indoor cats or cats prone to weight gain, the adult version’s more moderate protein load may actually be more appropriate than the kitten formula’s calorie-dense formulation.
Shared premium features. Both formulas include Instinct’s signature freeze-dried raw pieces mixed into the kibble, providing minimally processed nutrition alongside the cooked kibble. Both also include probiotics for digestive support. These features put even the adult version ahead of most B-tier competitors that don’t offer raw inclusions or probiotic supplementation.
Simpler protein profile for sensitive cats. If your cat has known protein sensitivities, the adult version’s narrower ingredient list (chicken and turkey only as primary proteins) makes it easier to identify and manage potential allergens. The kitten formula’s 6 protein sources across 5 species introduces more variables — great for complete nutrition, but harder to troubleshoot if digestive issues arise. Shop on Amazon →
The bottom line
Instinct Original Kitten is the clear winner here, and the 12-point margin is no fluke. The kitten formula delivers double the protein diversity, marine-sourced omega-3s from menhaden fish meal, and an ingredient profile that earns it a spot in our A tier — a grade only a handful of cat foods achieve. The adult Instinct Original is still a respectable B/78, with freeze-dried raw pieces and probiotics that keep it competitive in its class. But if you’re feeding a kitten or simply want the best Instinct has to offer for cats, the kitten formula is worth the investment.
Read our full reviews of Instinct Original Kitten and Instinct Original Cat for the complete ingredient breakdowns.