Infopet || Advice: Cats and Diet

Cats and Diet

A well fed-cat is a contented cat.
Mrs Katycat sleeps with a full tum.
Copyright Pat Meadows, 2002

Why does it matter what my cat eats?

Some cats can thrive on the cheapest cat foods and scraps, but not all cats can, and diet is an important way for owners to help their cats live long and happy lives. Not everyone agrees on all aspects of the best way to feed cats, though there are some general areas of agreement. We offer some answers to common questions here, with suggestions for further reading - see References at the end of this article.

Do check with your vet about the dosage if you want to give supplements. You run the risk of giving your cat an overdose of some minerals or vitamins if you don't calculate the dosage correctly, and they may not be necessary at all. Some commercial cat foods do, however, include additional taurine, an amino-sulphonic acid, deficiency of which is associated with retinal degeneration, heart disease and reproductive failure.

Check with your vet about diet too if your cat has a medical condition, since a change in food may help. Cats may have more than one medical condition, and you may need help to work out which takes precedence when making decisions on diet.

Sudden major changes in cats' diets can cause digestive upsets, so make radical changes, like a switch from processed to raw foods, gradually over a week or so, mixing some of the old food with the new. It's especially important to introduce new foods to kittens a little at a time. Kittens can develop allergies if their diets change suddenly, so it's safer to try one food at a time and a little at a time. Once your cat has got used to new foods, you can give him or her a varied diet, which helps to avoid finicky eating, eg refusal to eat if you can't buy a particular brand. Variety is also a good idea in case any particular food is not nutritionally adequate. Foods may be adequate according to today's wisdom, but new discoveries are being made all the time, so if you use more than one brand, you can offset any deficiency in a particular brand.

What are cats' nutritional needs?

There's general agreement that cats need proteins, fats and carbohydrates, as well as vitamins and minerals.

Proteins consist of amino acids and cats need them for cell and tissue growth, maintenance and repair. They can also be metabolised to provide energy. Cats need some 20 amino acids, 11 of which are called essential amino acids, and aren't synthesized in the body. Sources of protein are meat, fish, eggs and milk, but cats need animal tissue in their diets to stay healthy.

Cats also need fats for energy, which are broken down in the body to fatty acids and glycerol. Essential fatty acids are not synthesized by cats. Fat also provides fat-soluble vitamins, and is necessary to maintain coat condition. Fat sources include fish oil, milk and other dairy products and meat fat.

Carbohydrates are also a major source of energy in many species, but cats can survive without any, drawing on protein for any energy shortfalls. Complex insoluble carbohydrates, or fibre, is not digested but is important for the digestive system. Sources are cereal starches, and root vegetables.

Vitamins are needed in small amounts and are important in metabolic chemical reactions. Water soluble vitamins B and C can be synthesized by the cat itself. There are also fat-soluble vitamins, A, D, E and K. Sources of vitamins include fish oil, egg, vegetable oil, cereals, organ meat, yeast, fish and vegetables.

Minerals are split into two groups. Major minerals include calcium, phosphorus, sodium, potassium and magnesium. Micro minerals, or trace elements include iron, zinc, manganese, iodine and copper. They help to maintain pH balance and body fluids, regulate metabolism and are needed for muscle tissue function and conducting nerve impulses. They can be found in dairy products, meat, bone meal, cereals, and vegetables.

Water is vital for many bodily functions like transport of materials between tissues, pH balance, temperature control, blood and lymph medium, electrolyte balance and tissue cell lubrication. Sources include food, particularly canned - which has a high water content, and metabolic water produced from the metabolism of proteins, fats and carbohydrates in the body.

Feeding your cat properly involves more than just checking that food contains proteins, fats, and whatever. The nutrients also have to be accessible to the cat. Cats aren’t able to digest some foods well, for example, grain is not a good source of protein for cats, and does not provide all the amino acids they need. Many cats react to specific foods like cow's milk, and of course will be unable to benefit from nutrients in these foods if they vomit them, or get the runs. Meat and fish are good sources of protein for cats, which are carnivores to a much greater extent than dogs.

What one should look for in a commercial cat food - nutrients, ingredients and pet food labels

You're faced with an array of cat foods at the store. How can you decide what to feed your cat? First, check the labels and see what they tell you. You should find a list of both nutrients and ingredients, together with recommended servings. A typical label on feed bags or tins will include a Typical Analysis - giving moisture content, along with protein, fat, fibre, ash, calcium, phosphorous, magnesium and taurine levels in percentages. It will also list ingredients and provide a suggested daily feeding guide.

Pet food labels do not always say what form the vitamins and minerals are in, which can be a problem because some forms are more bioavailable than others. There are disagreements on what constitutes the correct levels of vitamins and minerals, but feline nutritionists agree that it is possible to give cats an overdose of some vitamins and minerals, so don't try vitamin supplements without advice from your vet. The ratios may also be important, eg ratios of omega 3 fatty acids to vitamin E, and these may be difficult to calculate.

The ingredients lists on can and pack labels can also be very vague when describing meat and fish, and may just describe meat as 'meat and animal derivatives', without saying where meat came from. This can be a problem if your cat is allergic to certain types of meat. Other labels may give information on which animals the meat comes from, but don't specify which body parts of animals are used. Likewise, there is little detailed information on what types of fish, and parts of the fish are used in cat foods containing fish. The important issue should be what is good for cats, rather than whether the source of food revolts you as a human. Cats may eat mice, skin, bone, stomach contents and all, and that is what they are designed to do, however revolting humans might find it. However, some things owners should worry about include drug residues in slaughtered animals used for pet food, and toxins resulting from E coli infections from long-dead animals. One concern about commercial foods is that pet owners have little way of knowing about the quality of ingredients used.

Additives

Many pet foods are now made without artificial additives, and sometimes cats with sensitive stomachs, such as Persians, will do better on such diets. There is disagreement on whether some additives are harmful to cats. ‘Natural’ does not necessarily mean ‘good’. Deadly nightshade is ‘natural’ and can kill people, while preservatives do have a use in ensuring that food retains nutritional value. However, many preservatives and colourings have not been around for long, so their long-term effects are unknown, and you may want to play safe.

Preservatives tend to be used in dry rather than canned commercial food, since canning is a way of preserving food. Once canned food has been opened it should be used on the same day, and any food left over from one meal should be stored in a cool place with a cover. Cats may not like to eat food cold from the fridge, but on hot days it's safer to store the food in the fridge, and you can then take it out half an hour or so before feeding.

There is some disagreement on whether cat-owners should avoid preservatives. Some preservatives, such as BHA may be carcinogenic, but evidence is mixed. Foods without such preservatives may be safer, however, dry commercial food without preservatives will deteriorate fast, a problem if owners are buying in bulk. It's best not to buy in bulk if you use a 'preservative free' dry food, and you need to store it properly in airtight containers, and use it before the ‘consume by’ date. Some foods have vitamin E added as a preservative, and this may be safer than BHA, but is also less effective as a preservative, so you still need to be very careful about using the food before its 'consume by' date.

Common sense says it's best to avoid highly coloured food. Your cat doesn't care what colour his food is, and is quite happy if it is sludge brown. Smell, taste and texture are more important for cats, and colourings are put there for humans. Avoiding highly coloured food means that you don't expose your cat to unnecessary risk. Flavour enhancers should also be avoided, not only because they may be harmful in themselves, but they may also incline cats towards obesity.

Pet food manufacturers themselves may refrain from using additives, but it is unclear whether the ingredients they use already contain additives. The resulting product may thus contain additives, though none has been added in the final manufacturing process. A claim that a product is 'additive free' is then no guarantee of quality, and some additives may be harmless, or even beneficial, but it's a start, since it's more likely that there are no unnecessary colourings and the like. There may also be links between skin allergies and behavioural problems and certain additives, which is one reason why home-prepared foods can be superior.

Dry or wet food?

Dry food is cheaper and more convenient. However, it may also contain more grain and preservatives, because grain is easier to store dry than meat, and canning is a way of preserving food. Cats need to drink more water if they are fed dry food, and are more at risk from dehydration, kidney and bladder problems if fed dried food and deprived of water. It's also easier to overfeed cats on dry food, since it is more concentrated, so you need tobe especially careful about amounts.

Comparing pet foods: maths is important

You need to be able to do some basic maths if you are comparing wet and dry foods, to be able to compare like with like, ie you need to remove moisture from the equation. It's also important to assess amounts per serving - a food may appear to have more of a vitamin if compared by dry weight, but if the servings are smaller, then the amount of the vitamin per serving will be reduced.

Getting information from pet food companies

Clearly, people whose cats have special needs don't have enough information on pack and can labels on which to base an informed decision. Even people whose cats seem to thrive on just about any food may be worried about the lack of information on packs and cans. UK packs may, for example, state that permitted preservatives are used, but not specify which preservatives. It is worth asking the companies for more information. They may not answer your phone calls, letters and emails, but they will know that owners do care about what goes into their cats' food. You will also be able to sort out which companies care about their reputations from the reponses, or lack of responses you get. Some owners believe that expensive foods are better foods, but the cost of pet foods may just reflect the marketing budget, rather than the quality of ingredients, the research carried out into selecting ingredients. However, a company that takes the trouble to answer your queries will care more about consumers that those which ignore you.

Is home-prepared food better than commercial food?

There's no simple answer to this question. Extreme supporters of pet food companies argue that only they are able to provide balanced diets for pets, and they stress risks of overdosing pets on supplements, or feeding cats inappropriate human foods. Yet parents manage to feed children adequate diets, even though children's needs differ from those of adults. Children's diets may be varied throughout the week, so that any imbalance in one meal can be compensated for in the next meal. Cat owners may also vary their cats' diets, for similar reasons. Studies on home-prepared food vs commercial food can be flawed if they group all homecooked food together. There's a world of difference between leftovers, given to a cat because they are cheap, and nutritionally balanced home-prepared feline meals. The worst home-prepared food may be worse than most processed food, which is at least designed for cats, but the best homecooked food can be better because the food can be prepared freshly for each meal. You also have more control over what ingredients go into meals, which is especially important for cats with food allergies, and you have more control over the quality of the ingredients.

Supporters of home-prepared foods argue that widespread usage of commercial food has led to a massive increase in a number of conditions, such as allergies and cancers. However, cancers may be more common these days simply because cats live longer, since they are more likely to be neutered and/or indoor cats, so less likely to roam and be run over. Commercial foods also vary a great deal in terms of quality, and it's as unscientific to lump them all together as it is to lump all 'home-prepared' food together. The main difference between commercial and home prepared foods is that commercial foods are prepared in bulk to be stored and sold, whereas home-prepared foods are made in smaller amounts and tend to be eaten fresh. Many cat owners don't have a lot of choice, and have to use commercial foods due to lack of time. It's difficult to read up on cat nutrition and prepare tasty, well-balanced recipes if you also work full-time. It's worthwhile doing some research on pet foods before making your choice of one or more brands, and sending emails to a few companies asking about their products doesn't take long. You do need to read widely on this topic if you want to feed your cat nothing but home-prepared food, so that you're aware of accepted practice and the debates in feline nutrition. You may not be able to do this, and may prefer to rely on commercial food for much of the time, and you can still prepare the occasional meal yourself without worrying about whether it is perfectly balanced in all aspects. There's nothing wrong with scraps so long as they fit into the cat's diet. You can check out cat recipe books for ideas on how to use your scraps. A home prepared diet could include; chicken, liver, rice, sterilized bone meal, iodised salt and sunflower or corn oil.

What foods should cats always avoid?

Cat are generally much more sensible than dogs about what they eat. They can, however, get digestive upsets from eating garbage, like rotting meat, that contains bacterial toxins. They are also at risk from rats and mice poisoned with rodenticides, so confiscate any rats and mice brought into the home if you live in an area where rodenticides may be in use. Cats can also be poisoned by some plants, so check that your houseplants are not toxic for cats.

What foods should cats only eat in moderation?

Both grain-based foods and cow's milk should only be given in small amounts. Cats aren't designed to be grain-eaters, nor to drink milk with lactose. Some cats seem to drink cow's milk with no adverse reactions, but they can't digest it easily and it's clear that some cats react badly to cows' milk. If your cat reacts by having diarrhoea, stop feeding him or her cow's milk altogether. There are special milk formulations which you can buy for hand rearing kittens, or for helping out queens with a lot of kittens. These formulations can be very expensive when bought from a vet in Britain, but you can buy them much more cheaply in some countries in mainland Europe, such as Spain. So, if you have friends going or living abroad, you could ask them to drop into a vet's and check out the prices.

Can cats eat commercial dog food?

Cats and dogs have different nutritional needs, so it's not a good idea to feed commercial dog foods to cats.

What about raw meat and fish?

Most cats allowed outdoors will supplement their diet with birds, small rodents and even goldfish, so they are already eating raw meat and fish. Cats catch themselves fresh meat, however, and it's important to ensure that meat and fish you give them is fresh, and from a reliable source, eg from a trustworthy local butcher. Toxins from one type of E Coli infection can lead to kidney failure and death. Fish should also be fresh, and it tends to go off faster than meat, so should be eaten on the same day you buy it. Why not share a fish with your cat, if the fish is too big for one cat? It's safer than storing it for the next day.

Are any foods good for sick cats?

The simple answer is yes, but it's worth checking changes with your vet if your cat is ill. There are specially formulated diets for cats suffering from Feline Lower Urinary Tract diseases, and those with chronic renal failure, where there is a risk of losing B vitamins in the high urine output.

Peter Markwell et al note that diet is important for cats with feline lower urinary tract disease, since it affects the volume and acidity of urine, and how concentrated it is. Research has tended to look at acidity levels, and concentration, as a way of dealing with uroliths. Uroliths may be of different types, however, and diets for cats with struvite uriliths may not be appropriate for calcium oxalate uroliths. Cats with lower urinary tract disease may also not suffer from uroliths at all. Increasing the volume of urine can help in tackling uroliths, and can help prevent crystals from forming. Research indicates that increasing the moisture content of cats' diets can more than halve the rate at which they suffer from recurrences of lower urinary tract problems, where the cause of the problem is not clear. Other factors, like urine proteins, may affect the formation of crystals, though more research is needed on this.

Kit Sturges has written on kidney problems, and notes that there is still too little knowledge about what cats with kidney problems should eat, and many recommendations come from work on species other than cats. Some changes, like protein restrictions are needed, but the actual protein level that a particularcat might need is unclear. Not all kidney diseases are the same, and cats are also genetically diverse. Cats may lack appetite when they are first ill, and they may not want to eat low-protein diets. They should eat something, since this is better than their breaking down body protein. Appetite stimulators can help. Older cats may do well on a 'geriatric' diet geared to declining intestinal function, which is a characteristic of older cats.

Tim Watson has studied diet and skin disease, and notes that cats with skin disease may need a change of diet to ensure they are getting enough vitamin E, and the proportion of vitamin E to other ingredients in their diet may also be important.
Vitamin E deficiency can affect cats fed oily fish, and more vitamin E is needed as polyunsaturated fatty acid (PUFA) intake increases. Vitamin B deficiency can also be linked to skin problems, and brewers yeast, or other supplements that provide the whole B group can remedy this. Skin diseases often clear up if better quality food is given to cats, or if more care is given to storing cat food properly, so nutrients are not lost.

How much food should I feed my cat?

There's is no simple answer to this question. Cats vary a lot in terms of how fast they burn up food. Very active outside cats need to eat more, as do pregnant and lactating queens. How much depends a lot on how many hungry kittens they have to feed and on the breed. Other factors that affect how much food cats need include their age and condition.

An adult cat has a daily energy requirement of between 60 and 90 Kcal/kg body weight, depending on rates of activity. At least 25% of the diet should be in protein form. Typically, canned food will provide around 70 Kcal/100g. Cats will generally adjust their daily food intake to suit their energy requirements.

Kittens increase their body weight by around 100g/week in the first few weeks of life. Growth rates at around 4 weeks of age are extremely high and nutritionally demanding. Kittens should have several small meals a day (4 or 5) when they are weaned at 8 weeks, as their stomachs only have a small capacity. They should be fed a diet specially formulated for growth.

Breeding Queens have an energy requirement of 100 kcal/kg/day during gestation (compared to approx 70 kcal/kg pre-mating) and around 240 kcal/kg/day during lactation. The queen will usually start to eat more just a week after successful mating. Frequent meals should be available and even kitten food can be fed, which is concentrated. This helps because the queen's stomach has limited ability to expand, when kittens are taking up room in her abdomen.

Elderly cats will have slightly different dietary requirements, and although an adult maintenance diet can still be fed, it may need to be supplemented with minerals, and vitamins, particularly B vitamins that are water-soluble and will be flushed out as the kidneys become less efficient. There are specially formulated commercially prepared diets for elderly cats, both in dried and canned form. Some elderly cats may prefer to eat canned food if they develop dental problems or lose teeth as they age. There are elederly cats which have very few teeth left and still manage to eat dry cat food very successfully! Older cats may have difficulties digesting food and if this is not due to illness, your vet may prescribe a digestive aid, such as Pro-zyme, a mixture of enzymes and probiotics.

Convalescent cats may not want to eat, but their energy needs increase, so energy-rich food can be warmed up to stimulate interest in food. Otherwise, offer favourite foods or strong smelling good such as pilchards or sardines. There are also specially formulated commercial convalescent and recovery diets available.

Indoor Cats may lead a more inactive lifestyle than cats with access to outdoors, so they will only require around 50 kcals/kg/day. Pet food manufacturers are just starting to introduce specially formulated diets for indoor cats. Royal Canin claims to be the first, and their Indoor 27 takes into account constant coat moulting, lower activity levels leading to slower digestion and the tendency to gain weight.

Obesity is often a problem with indoor cats, and those that prefer not to go out much. Be careful about putting your cat on a crash diet, though - cats subjected to rapid weight loss may lose too much lean tissue.

Cat nutrition books provide tables, as well as recipes for homecooked meals. Go by manufacturers' recommendations, if you use processed foods, and try to select a formulation for your cat's type, age and lifestyle. The amounts recommended are just guidelines, though, not rigid rules. Treats and scraps need to be included in calculations. Adjust amounts if your cat leaves food in his or her bowl, or appears to be getting too skinny or too fat.

Can I give my cat a vegetarian diet?

It is not advisable. Cats are designed to be carnivores, and it is very difficult to feed them properly without giving them meat and fish.

What sort of feeding and watering equipment do I need for my cat?

Food bowls should be wider than the cat’s whiskers, as cats dislike narrow bowls and will usually take the food off them and eat it off the floor! There are many different types of feeding bowls including ceramic, glass, stainless steel and plastic. Plastic bowls may become scratched after a time and therefore more difficult to clean thoroughly. Ceramic, glass and stainless steel are all easier to keep clean, but ceramic and glass are also easy to break! Automatic feeding bowls are useful in emergencies if the cat has to be left alone for longer than usual.

Fresh, clean drinking water should always be available; despite this however, cats may instead prefer to drink from puddles outside in the garden. Cats are very sensitive to the chemicals used to treat water and this, together with the fact that water bowls may also smell of detergent, means they prefer the more ‘natural’ smell of puddles and pools. Therefore, water bowls should be thoroughly rinsed after washing and the water allowed to stand to allow chemicals to dissipate.

Food and water bowls should be washed in detergent and hot water and rinsed thoroughly. There are also anti-bacterial disinfectants available specifically for feeding bowls, such as Friends Feeding Bowl Cleaner and Pet Virkon. Make sure that any disinfectant does not contain phenols, which are toxic to cats.

What can research on cats and diet tell us?

Scientific methods have shown why certain foods are good for cats at different stages of their lives, and in different situations (eg indoor or outdoor cat) but nutritional guidelines can change as scientists find out more about the particular needs of cats. Sometimes studies are only short term, and the long-term effect of a particular ingredient may be unknown. Research by pet food companies can be useful, since, like owners who prepare their own cats' food, the companies want to find out what ingredients to use. However, pet food companies may focus more on different aspects of diet from those which interest pet owners. Palatability, for example, may rank high on a pet food company's list of priorities, so they can claim that cats love their food. However, the owner of an obese cat may want to avoid foods that are very palatable! Use your common sense when reading scientific research - check, for example, that the conclusions are in line with what the article actually says. This is not always the case - sometimes the conclusion and the abstract (summary) sound as though the findings are more reliable than is warranted by the research. Be wary of reports in popular journals, and read the original research if you are able to - it may be slow going at first, but is well worth it. Ask your vet to check out interesting articles you find - vets are better able to interpret research than the average owner. The more you read, though, the better you will be able to make sense of new research, and this is a fascinating area.

References

Books

Cutts, Paddy The Complete Cat Book

Delmonte, Patti Real Food for Cats, Storey Books

Dallas, Sue Animal Biology and Care

Fogle, Bruce Natural Cat Care

Morris, Desmond Illustrated Catwatching

Strombeck, Donald Home Prepared Dog and Cat Diets Iowa State University Press

Turner, Trevor and Jean Turner (eds) Veterinary Notes for Cat Owners

Articles

Butterwick, Richard F. and Amanda J Hawthorne 'Advances in dietary management of obesity in dogs and cats' Journal of Nutrition vol 128 no 12, December 1998

Markwell, Peter J. et al 'The effect of diet on lower urinary tract disease in cats'
Journal of Nutrition vol 128 no 12, Dec 1998

Sturges, Kit 'Dietary news for cats' Feline Advisory Bureau vol 38, 1 p18

Watson, Tim D.G. 'Diet and skin disease in dogs and cats' Journal of Nutrition vol 128 no 12, Dec 1998

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