Can Adult Cats Eat Kitten Food?

Last Updated on August 8, 2021 by Julia Wilson

Can adult cats eat kitten food?

An adult cat with no underlying medical conditions can eat kitten food, but kitten food should not be a regular part of an adult cat’s diet unless medically indicated. Kittens have higher energy requirements than an adult cat and kitten food is specially formulated for optimal growth and development with higher protein and fat levels compared to adult cat food. Kitten food that is consumed by an adult cat won’t cause any short-term harm, however, the extra calories will lead to weight gain, which does have detrimental health implications.

Looking at the AAFCO  minimum dietary requirements chart (listed at the end of the article) of kittens compared to adult cats, you can see the following: 

  • Protein requirements are 30% for kittens compared to 24% for adult cats
  • Docosahexaenoic acid (DHA) is 0.12% for kittens, DHA which is an essential fatty acid in cat breast milk which is critical for brain and vision development, there is no determined amount for adults
  • Calcium requirements for kittens are 40% greater than adult cats
  • Phosphorous requirements for kittens are 60% greater than adult cats

Most excess vitamins and minerals will be excreted out of the body, however, vitamins A and D are fat-soluble, and it is possible for cats to have too much. Looking at the differences in vitamins A and D in kitten food vs adult food, the extra amount will not cause an issue for adult cats.

So, there’s nothing in kitten food that is detrimental to a healthy adult cat with no underlying medical conditions, however, it is more calorie-dense and can lead to weight gain if fed regularly.

Not all adult cats can eat kitten food

Even small amounts of kitten food can impact an adult cat who has underlying medical conditions. Many pre-existing medical conditions are managed either in part or wholly by feeding a veterinary prescribed diet. This includes cats with kidney disease who should eat a low phosphorous diet, cats on a hypoallergenic diet or food trial, cats with inflammatory bowel disease, heart disease and cats with struvite bladder stones on stone dissolving diets.

Feeding an adult cat and a kitten in the same household

It can be hard to keep adult cats away from kitten food, in the multi-cat household. If practical, feed both cats in separate rooms to prevent the adult from eating his or her own food and moving in on the kitten’s food.

Microchip feeders are another way to tackle this. Each food bowl is activated by the cat’s individual microchip number.

How to calories should a kitten and adult cat eat per day?

The following formula makes it easy to calculate the calorie needs for kittens and cats by first working out the resting energy requirements. Resting energy requirements (RER) is how many calories the cat needs at rest, at a controlled temperature.

RER formula for cats

The following formula is the same for all cats, regardless of age and weight.

30 x (body weight in kilograms) + 70 = RER

Once you have calculated the RER, you then need to multiply by the following figures to get the daily calories

  • Kittens: RER x 2.5
  • Adult cats (desexed maintenance): RER x 1.2
  • Adult cats (entire, maintenance): RER x 1.4
  • Obese prone: RER x 1
  • Weight loss: RER x .8

As you can see, the kitten needs just over twice the calories per kg as the adult on a maintenance diet.

How long should a kitten eat kitten food?

A cat is considered an adult by the time he or she reaches 12 months old, and during this time should transition to adult cat food. The only exception are the large, slow-growing breeds including the Birman, Ragdoll and Maine Coon who can take 3-4 years to reach maturity. Check with your veterinarian if you have a larger breed to make sure they switch over at the optimal time.

Do any adult cats benefit from kitten food?

In some circumstances, your veterinarian may recommend an adult cat switch to a kitten food diet. This includes the following groups:

  • Pregnant cats
  • Lactating cats
  • Underweight cats

How to safely transition from one food to another

When you are transitioning a cat from one type of food to another, do so gradually to avoid gastrointestinal issues. On day one, mix a small amount of the new food in with the old, and gradually mix in more of the new food and less of the old food over a 5-7 day period.

Selecting the right food for your kitten or cat

You get what you pay for, cheap brands contain more fillers and can be a false economy if the cat isn’t getting all the nutrients he or she needs. All cat foods should be labelled ‘complete and balanced‘ which means it meets the requirements of AAFCO.

Choose the appropriate food for your cat’s age and lifestyle. I personally like to mix and match a little with canned, dry and raw so a) the cats don’t get bored and b) they’re used to a variety of foods. If you decide to feed a home-prepared diet, speak to your veterinarian who can help you create a balanced diet or who can refer you to a nutritionist. An incomplete home-prepared diet that is lacking in essential nutrients can have a serious and lasting impact on a cat’s health.

Dry matter basis (DMB)

Protein is the building block of the body and kittens need protein for growth. Not all food is created equal. DMB relates to how much protein is in the food once all the moisture has been removed. Two of the three Australian brands of food I have do not list the moisture content. The average can of wet food contains a moisture content of 70%. To calculate the dry matter minus the percentage of moisture from 100. Then divide this figure by the percentage of protein.

Dry matter percentages of three brands of food:

Brand A – Cheap supermarket tinned food
Protein 8.5% Moisture 70% 100 – 70 = 30 / 8.5 = 28.33% dry matter protein
Brand B – Expensive ‘gourmet’ supermarket tinned food
Protein 12% Moisture 70% 100 – 70 = 30 / 12 = 40% dry matter protein
Brand C – Premium dry food
Protein 32% Moisture 10% (as stated on pack) 100 – 10 = 90 / 35.5 = 39.4% dry matter protein

Brand B, the expensive ‘gourmet’ brand contains the highest % of dry matter. However, quantity doesn’t necessarily translate to quality. Check to see what the first ingredient is on the product. Is it meat, meat by-product or something else?

AAFCO cat food nutrient profiles based on calorie content

    Growth and reproduction (minimum) Adult Maintenance (minimum) Maximum
Crude protein % 30.00 26.00  
Arginine % 1.24 1.04  
Histidine % 0.33 0.31  
Isoleucine % 0.56 0.52  
Leucine % 1.28 1.24  
Lysine % 1.20 0.83  
Methionine % 0.62 0.20 1.5
Methionine-cystine % 1.10 0.40  
Phenylalanine % 0.52 0.42  
Phenylalaninetyrosine % 1.92 1.53  
Threonine % 0.73 0.73  
Tryptophan % 0.25 0.16 1.7
Valine % 0.64 0.62  
Crude fat % 9.0 9.0  
Linoleic acid % 0.6 0.6  
alpha-Linolenic acid % 0.02 Not determined  
Arachidonic acid % 0.02 0.02  
Eicosapentaenoic + Docosahexaenoic acid % 0.012 Not determined  
Calcium % 1.0 0.6  
Phosphorous % 0.8 0.5  
Potassium % 0.6 0.6  
Sodium % 0.2 0.2  
Chloride % 0.3 0.3  
Magnesium % 0.08 0.04  
Iron mg/kg 80 80  
Copper (extruded) mg/kg 15 5  
Copper (canned) mg/kg 8.4 5  
Manganese mg/kg 7.6 7.6  
Zinc mg/kg 75 75  
Iodine mg/kg 1.8 0.6 9.0
Selenium mg/kg 0.3 0.3  
Vitamins and others        
Vitamin A IU/kg 6668 3332 333300
Vitamin D IU/kg 280 280 30080
Vitamin E IU/kg 40 40  
Vitamin K mg/kg 0.1 0.1  
Thiamine mg/kg 5.6 5.6  
Riboflavin mg/kg 4.0 4.0  
Pantothenic acid mg/kg 5.75 5.75  
Niacin mg/kg 60 60  
Pyridoxine mg/kg 4.0 4.0  
Folic acid mg/kg 0.8 0.8  
Biotin mg/kg 0.07 0.07  
Vitamin B12 mg/kg 0.020 0.020  
Choline mg/kg 2400 2400  
Taurine (extruded) mg/kg 0.10 0.10  
Taurine (Canned) mg/kg 0.20 0.20