easiest proteins for cats to digest
Cat Food and Hydration

What’s the Most Easily Digestible Protein for Cats?

Cats need a high-protein diet to survive, but consuming large amounts of protein can be harsh on cats with sensitive stomachs. It doesn’t help that the proteins found in many commercial cat foods are low-quality and somewhat difficult to digest. To prevent digestive problems, we’re often told to feed our cat ‘high quality’ or ‘digestible’ protein instead.

What is the most digestible form of protein for cats? Cat food that contains a single, identifiable protein (i.e., chicken) is more digestible than cat food that contains rendered meat products (such as ‘meat meal’ or ‘meat byproducts’) because more of the amino acids are retained. Also, animal proteins contain more amino acids than plant-based proteins.

If you feed your cat ‘high-quality’ and ‘digestible’ protein, this will improve their bowel habits and their general health. Many chronic diseases are caused or aggravated by a diet that’s low in protein (or low in quality protein).

Why Is Protein Important for Cats?

Cats have higher protein requirements than either dogs or humans. But why is dietary protein so crucial for cats? It’s not the protein that’s important but rather the amino acids that are found inside the protein.

Cats use these amino acids to build new proteins at the cellular level (protein synthesis). Like all living things, cats need to make new proteins to stay healthy and function normally. Also, some of these amino acids help to convert glucose into energy.

There are 11 ‘essential’ amino acids that cats must get from their diet. These include:

Arginine

The AAFCO states that arginine should be at least 1.04% of the crude protein (in dry cat food). Arginine is a vital amino acid because it helps cats to get rid of ammonia through their urine.

If a cat is deficient in arginine, they won’t have the enzymes required to expel ammonia, so they’ll develop ammonia toxicity. Studies show that a single meal devoid of arginine can make a cat sick.

Taurine

If cats don’t get enough taurine in their diet, they may develop blindness, deafness, congenital disabilities, and even heart failure. This deficiency usually develops over several weeks or months.

Vigilant owners and vets may be able to intervene and reverse some of the damage by placing the cat on a high-taurine diet, but action must be taken early.

Lysine

According to the AAFCO, lysine should account for at least 0.83% of the crude protein in dry cat food. Deficiencies in lysine are not uncommon, especially in kittens.

This is because cat food processing techniques can damage the integrity of lysine. Symptoms of lysine deficiency include skin lesions and scratching – particularly on the face.

In addition to amino acids, cats also obtain a variety of vitamins and minerals from protein (i.e., vitamin A and folate).

Most easily digestible protein for cats

What Is the Best Protein Source for Cats?

You’ve probably heard vets say that cats are ‘obligate carnivores.’ This means that they must eat animal protein to survive. Most specialists agree that a meat-based diet (combined with small amounts of starch and plant-based protein) is the healthiest diet for a cat.

This is because animal proteins have a higher ‘biological availability’ than plant-based proteins. In other words, animal flesh can provide a cat with more of the amino acids, vitamins, and minerals that they require, so it is considered a more ‘complete’ food source.

To be specific, amino acids such as taurine, arginine and arachidonic acid are not available in plant-based proteins. Also, cats are unable to convert the beta-carotene from plants into vitamin A so they must obtain preformed vitamin A from animal protein.

That’s not to say that any old meat will do; ‘digestibility’ is just as important as ‘biological availability.’ Your cat needs to be able to digest the protein effectively. Otherwise, the vitamins, minerals, and amino acids will go to waste.

Why Is Digestibility Important?

Dietary protein can only be beneficial to cats if it is absorbed and digested effectively. That’s why, as cat owners, we’re often advised to purchase cat food that contains ‘digestible’ or ‘high-quality’ forms of protein.

If your cat is unable to digest the protein you serve up, they may become deficient in an essential nutrient.  As mentioned, arginine deficiency can develop in a matter of hours if the cat hasn’t absorbed enough of this vital amino acid.  To promote good health, you should opt for pet food that has a dry matter digestibility of at least 80%. 

Unfortunately, this is easier said than done. Pet food companies are not obliged to print digestibility information on the label (though they will have tested digestibility when developing the product so they should have this information available). If you dig around, you might find the digestibility % on the manufacturer’s website.  

Also, you can take a look at the ingredients list to get a rough idea of how digestible the food is going to be. Here are the digestibility ratings for the following cat food ingredients:

  • Cooked Egg Whites – 98% (near perfect in terms of digestibility)
  • Muscle Meat (chicken, rabbit, turkey) – 92%
  • Organ Meats (kidney, liver, heart) – 90%
  • Fish – 75%
  • Soy – 75% (though some recent studies suggest that processing soy in a different way can make it more digestible for cats)
  • Corn – 54%

Animal-based proteins are generally more digestible than plant-based proteins. However, it’s not enough to feed your cat a cooked egg or some muscle meat.

You should balance the macronutrients (fat, carbohydrate, protein) in your cat’s diet to promote good digestive health. It’s difficult for cats to digest carbs.

Factors that Affect Protein Digestion in Cats

A cat’s ability to digest protein is determined by many different factors. If you want your cat to digest protein effectively, you should consider the following factors:

  • The ‘quality’ of the meat in your chosen cat food – particularly how the meat was processed.
  • The number of meats being used in one cat food – too much variety can be overwhelming for a sensitive stomach.
  • The protein content of the meal (along with the balance of other macronutrients).
  • Whether the meat in your cat’s food mimics their natural prey. Could they catch it in real life?
  • Your cat’s overall gut health (this can be influenced by other dietary ingredients such as fiber and pre/probiotics)
  • The age and health status of your cat – cats have different protein requirements throughout their lifespan.

Signs of Poor Digestion in Cats

If your cat uses the litter box once every couple of days and their poop is reasonably firm, this indicates good digestive health. On the flip side, if your cat is struggling to digest their meals, you’ll notice some of the following symptoms:

  • Larger stools than normal
  • Poop is smellier than usual
  • Loose stools
  • Pooping more than once a day
  • Flatulence and bloating
  • A dull coat
  • Lethargy
  • A reluctance to eat the food provided
  • Weight loss
  • Diarrhea

If these symptoms carry on for more than a day or two, you should introduce a more digestible cat food (If symptoms such as diarrhea and vomiting persist for over 24 hours, you should see your vet).

Choosing a Cat Food with High-Quality Protein

Most pet care websites will advise you to feed your cat ‘high quality’ protein because it’s easier for them to digest. But what is meant by high-quality protein?

There is some controversy surrounding this issue, but identifiable muscle meat/organ parts are considered high-quality proteins. These should be listed first on the ingredients list.

best protein source for cats

For example, look for labels that contain: ‘chicken,’ ‘lamb,’ ‘rabbit,’ ‘pig’s heart,’ ‘pig’s liver’ etc., at the top of the ingredients list (as opposed to ‘meat meal’ or ‘byproducts’). Studies have shown that muscle meats and organs are highly digestible forms of protein for cats.

Studies have shown that eating a single, non-rendered protein (as opposed to ‘meat meal’ or ‘meat byproduct meal’) helps cats absorb more of the amino acid lysine (and perhaps also more vitamin A, D, & E). So, look for cat food that contains meat/organs from a single, identifiable source at the top of the ingredients list.

Is ‘Meat Meal’ Digestible for My Cat?

If you see ‘meat meal’ written on the ingredients label, this means that the protein has been rendered. Rendering involves heating the animal flesh to a very high temperature to remove excess moisture and fat – thereby creating a concentrated form of protein.

In some ways, this is good because it makes the product more cost effective and easy to transport. However, it’s thought that ‘meal’ is not as digestible as untreated meat. According to this study on OUP, the rendering process can damage the integrity of lysine.

The evidence is sparse in this area, so we’re unsure if the rendering process negatively impacts any other amino acids – but some scientists believe many more amino acids will be affected.

Also, ‘meat and bone meal’ should be avoided because high levels of bone can prevent the absorption of amino acids.

The other issue with ‘meat meal’ is that it doesn’t specify which animal(s) the meat has come from. ‘Meat meal’ could contain the meat of many different mammals (not just chickens, cattle, sheep, pigs, and goats).

Though variety might seem like a good thing from a nutritional perspective, research indicates that feeding your cat too many different proteins can cause digestive issues. 

If you want to be certain about where the animal protein has come from, look out for labels where the meat is specified, i.e.: ‘chicken meal’ or ‘lamb meal.’

Though if your budget allows it, stick to cat foods that only use ‘meals’ in small amounts (i.e., printed further down the ingredients list).

Are ‘Meat Byproducts’ Safe for My Cat?

According to AAFCO, ‘byproducts’ includes, but is not limited to, lungs, spleen, kidneys, brain, livers, blood, bone, partially defatted low-temperature fatty tissue, and stomachs and intestines freed of their contents. In the case of poultry, it also includes heads, feet, and entrails.

So, are byproducts safe for a cat to consume? Again, one of the issues with byproducts is that you don’t know exactly which animal your cat is consuming.

If your cat has a sensitive stomach and then has a reaction to a particular food, it will be impossible to know what has caused the reaction.

Moreover, some argue that animal fur/hair, fecal matter, plastics, and other unpalatable (possibly unsafe) ingredients are present in ‘meat byproducts’ because it’s too costly/time -consuming for manufacturers to remove these parts.

At this time, there’s little evidence to suggest that byproducts are genuinely unsafe for cats. However, ‘meat byproducts’ probably aren’t as digestible as higher-quality proteins (partly because they need to be rendered to be safe for cats to consume). It’s best to avoid this ingredient.

Which Meat Is Best for Cats?

Unprocessed, whole meat is generally more digestible than ‘meat meal’ or ‘byproducts,’ but which animal flesh offers the best source of protein for cats?

Some specialists say that feeding a cat an animal they could reasonably catch in the wild is most beneficial. This would include:

  • Chicken
  • Turkey
  • Rabbit
  • Fish (in moderation) – According to Nottingham University, fish can contain high levels of arsenic so should only be consumed once or twice a week.

Lamb is commonly used in cat food. Several studies, including this one from NCBI, have shown that lamb is poorly digested when compared to other meats.

The amino acids cysteine, lysine, and threonine are absorbed less efficiently from ‘lamb meal’ – perhaps because the wool is not adequately separated from the protein. 

Beef is commonly used in cat food because it is a cheap form of protein. When a cat has a food intolerance or allergy, vets often suggest eliminating beef first (many hypoallergenic cat foods don’t contain any beef).

So, if your cat has a sensitive stomach, steer clear of cat foods containing beef.

Wet vs. Dry Food for Cats

Digestibility is often higher in wet food compared to dry. This is because wet food goes through fewer stages of processing so the amino acids may be more intact.

Dry food (containing a ‘meat meal’) has gone through a ‘double-processing’ – once when the meat was rendered and again when the mixture was made into kibble. As mentioned, the high processing temperatures can degrade lysine and perhaps other amino acids.

If you want to increase your cat’s intake of protein, you might be wondering whether it’s best to feed your cat wet food or dry food (kibble). If you compare two packets, it will probably seem as if dry food has more protein that wet. However, this is quite misleading because you cannot directly compare the two labels without doing a few extra calculations.

This resource from the FDA shows you how to compare the protein content of wet and dry food on a ‘dry feed’ basis. Generally speaking, wet food contains more protein than dry food, once you take the moisture content into account.

That’s not to say that dry food is all bad. Kibble may help to keep your cat’s teeth healthy, and it adds variety to your pet’s diet. Most vets would recommend feeding your cat a combination of wet and dry food to ensure they stay healthy.

Is Raw Cat Food More Digestible?

If unprocessed meat is better for cats than ‘meat meal,’ does this mean that an uncooked diet would be optimum? Wild cats eat a raw diet, so it seems like the most natural option to feed your pet.

According to this study on Sage, a raw meat diet is highly digestible for cats. Many owners also claim that their cat’s poop is less smelly on a raw diet. Though raw food is digestible for cats, there are some potential dangers to be aware of:

  • Raw meat diets have been linked to fat deficiencies (total fat and essential fatty acids)
  • The risk of bacterial infections increases

If you plan to feed your cat a raw diet, choose a reputable pet food manufacturer. Raw meals must be nutritionally balanced and prepared safely, so select a seller you can trust. You shouldn’t try to prepare a raw food diet yourself as it could be deficient in critical nutrients.

How Much Protein Do Cats Need?

Protein requirements change throughout the life span. Here are the recommended allowances for crude protein:

  • Kitten – 10g
  • Adult Cat – 12.5g
  • Nursing Cat – 41g

The AAFCO has set the minimum level of crude protein at 26% for any cat food labeled ‘complete.’ However, most vets consider a ‘high-quality’ cat food to contain 40-50% protein (this is closer to the amount of protein a wild cat would consume).

It was previously believed that older cats (10 years+) should not be fed protein (because their bodies struggle to digest it). However, it’s now known that older cats do require protein, but that it needs to be in a very digestible form so their bodies can tolerate it.

plant-based proteins vs. animal proteins for cats

Cat Food Ingredients that are Bad for Digestion

Some commonly used cat food ingredients can interfere with digestion. Besides ‘meat meals’ and ‘byproducts,’ you should be wary of the following ingredients:

  • Ash – If the ash content is above 5%, this suggests there’s quite a lot of bone in the cat food, which may impact protein absorption.
  • Phytate – This is a plant-based ingredient that can stop your cat from absorbing essential minerals.
  • Corn or Corn Meal – This is a very cheap ‘filler’ for cat foods but is only about 54% digestible for cats.
  • Butylated Hydroxyanisole (BHA), Butylated Hydroxytoluene (BHT) – These chemicals are sometimes found in cat treats; they are known to be carcinogenic and may cause kidney/liver damage.
  • Carrageenan – This is derived from seaweed and is used to thicken pet food. It can cause gastric inflammation in cats.

The above ingredients should be avoided wherever possible.

What Else Influences Digestive Health?

The protein you feed your cat will have a significant influence on digestive health, but there are other important factors to consider, too. For example:

Fiber

Is your cat getting enough fiber in their diet? Studies have shown that certain fibers (i.e., beet pulp) can have a very positive impact on the cat’s gastrointestinal (GI) health and bowel movements.

This is one of the reasons why dietary carbohydrates should not be eliminated from a cat’s diet.

Adjustment Period

If you change your cat’s wet/dry food, it can take several weeks for them to adjust to the new ingredients – especially as commercial cat foods often contain a long list of different ingredients.

For this reason, it’s advisable not to change your pet’s diet too frequently.

Pre/Probiotics

If your cat has poor digestive health, they may benefit from pre/probiotic supplements. You should speak to your vet before supplementing.

Stress

Stress affects a cat’s digestive health. If your cat feels under threat at meal times, they may eat their food too fast – leading to poor digestion.

Studies show that irritable bowel syndrome (IBS) is caused or worsened by stress in some cases.

Allergies and Intolerances

Food allergies are not uncommon in cats. Consuming an allergen (such as beef, milk, eggs, gluten) will likely cause vomiting and diarrhea.

Protein Requirements for Cats with Kidney Problems

Cats with kidney problems should be fed a specialist cat food. These cat foods often contain:

  • Smaller Amounts of High-Quality Protein – When animal protein is broken down, toxic byproducts are produced which exit the cat’s body in urine. If your cat has kidney problems, they won’t be able to expel these toxins very efficiently, so they’ll start to feel very sick. This is why senior cats with kidney problems need small amounts of highly-digestible protein.
  • Low Levels of Phosphate – Phosphate speeds up the development of kidney disease. Any cat with kidney problems should be fed a low-phosphate diet.
  • Higher Levels of Omega-3 Fatty Acids – This is to improve blood flow to the kidneys.
  • Strong Meaty Smell – These specialist cat foods have a strong, meaty flavor to entice older cats who may have a poor appetite.

You’ll find that most of these specialist cat foods are wet. Cats with kidney disease are prone to dehydration, so it’s better to feed them wet cat food.

Plant-Based Protein vs. Meat Protein

Cats require 11 essential amino acids (and several other vitamins and minerals) to survive. Plant-based proteins can provide some, but not all, of these amino acids, vitamins, and minerals.

To be specific, the following amino acids, vitamins, and minerals can only be obtained from animal flesh (or synthetic supplements):

  • Preformed Vitamin A (cats cannot convert beta-carotene into vitamin A like other species can)
  • Arachidonic Acid (cats cannot convert linoleic acid into arachidonic acid like other species can)
  • Taurine
  • Arginine

Many cat foods contain small amounts of plant-based protein/carbohydrate. If cooked properly, these are considered to be healthy when eaten in moderation.

Can Cats Eat a Vegetarian or Vegan Diet?

Most specialists would say that a purely vegetarian or vegan diet is unacceptable for cats.

However, a small number of vets, scientists, and pet food manufacturers are in favor of a veggie diet for domestic cats.  According to this review on MDPI, feeding our cats a plant-based diet could make sense for many reasons. For example:

  • Cats need nutrients not ‘protein’ per se. We can synthetically produce the amino acids/vitamins/minerals only available from meat and add these to plant proteins. Synthetic taurine is added to most meat-based cat foods to ensure the AAFCO requirements are met.
  • Food technology is advancing rapidly; although veggie pet foods are expensive at the moment, it’s thought they will become much more cost effective than conventional meat-based pet foods in the long term (especially if demand increases).
  • Although poorly managed vegetarian diets can cause a whole host of health problems for cats (including blindness and heart failure), studies show that a responsibly managed vegetarian diet (i.e., specially formulated cat food that sticks to AAFCO nutritional guidelines) is no less healthy than a conventional diet.
  • Plant-based proteins can be highly digestible if prepared appropriately.
  • A meat-based diet is considered best because it is ‘natural’ but keeping cats as pets is not natural so our logic may be skewed in this regard.

According to this review, you should only consider a vegetarian diet for your cat if you are willing to purchase a ‘complete, nutritionally balanced’ veggie cat food and check the PH of your cat’s urine on a semi-regular basis.

Take advice from your vet before making any significant dietary changes to ensure your cat stays healthy.

How to Improve Your Cats Digestive Health

In this article, we’ve explored what is meant by ‘high-quality’ and ‘digestible’ protein for cats. Let’s recap the key points you should remember when choosing a cat food:

Protein-Rich Cat Food

Cats have relatively high protein requirements, so ensure the cat food is rich in protein. Choose a cat food with 40-50% crude protein (except if your cat has kidney problems).

Ensure your cat gets 12.5g of protein a day (41g if pregnant).

High-Quality Protein

The price is a good indicator of protein quality, but it’s important always to check the ingredients list. Choose a cat food with identifiable meat/organs on the label.

For example, Chicken, Rabbit, Pig’s Heart. ‘Chicken meal’ or ‘Rabbit meal’ is fine in smaller amounts, but you should generally avoid ‘Meat meal’ or ‘Meat byproducts’ so you can be sure exactly what your cat is consuming.

Digestibility %

Cat food manufacturers who believe in their products will often post digestibility information on their website, so do your research before trying out any new pet food.

Look for a ‘dry matter digestibility’ of at least 80%. Cooked eggs, muscle meat, and organ meat are generally considered to be the most digestible sources of protein for cats.

Fewer Ingredients

The longer the ingredients list, the harder your cat’s digestive system has to work to process them. It’s best to choose a cat food that has only one or two sources of protein (that’s why you should avoid meat meal).

Also, avoid unnecessary/undigestible ingredients such as phytate, carrageenan, and colorings.

Avoid Preservatives

Look for cat food without preservatives (such as Butylated Hydroxyanisole and Butylated Hydroxytoluene). Cat-friendly preservatives include tocopherols (Vitamin E) and rosemary oil.

Wet Food

In terms of protein content, digestibility, and weight management, wet food is generally preferable to dry food. There’s nothing wrong with small amounts of kibble, but they shouldn’t make up the bulk of your cat’s diet.

Raw Food Diet

If your cat’s poop is very smelly, or they’re refusing many conventional cat foods, you could try them on a raw food diet. There is evidence to suggest that this protein is highly digestible, but you should ensure the cat food is nutritionally balanced.

Fiber

Choose a cat food that has a small amount of beneficial fiber (such as beet pulp).

Monitor your Cat

You should monitor your cat regularly to check they are digesting their food effectively. A healthy cat will poop once every 1-2 days. The stools should be reasonably firm and not too smelly.

Minimize Stress

Make sure your cat feels calm and in-control at meal times. For example, you should always feed cats separately and try not to disturb them while they are eating. If your cat is prone to eating too quickly, use a feeder that slows down their eating.

Specialist Cat Foods

If your cat has kidney disease they will struggle to digest the protein in conventional cat foods. Cats with renal problems must be fed a specialist diet.

See your Vet

Poor digestion can be caused by a variety of factors such as allergies, IBS, or other chronic illnesses. You should see your vet if the symptoms of poor digestion do not improve and you want to change your pet’s diet.

Cats are hardy creatures, but they can struggle to digest some of the ingredients found in cheap, commercial cat foods. To promote good health and prevent disease, try to choose only high-quality and digestible cat food for your pet.