Regular dry pet food contains grains such as wheat, barley, corn and rice, and they're sometimes used in wet food to provide fibre. Mirroring human dietary trends, grain-free products for pets are becoming increasingly popular.
Note that just because a dry food is grain-free, that doesn't mean it's carbohydrate free. Kibble requires some sort of starch to hold the meat and fat together, so vegetables such as potato, sweet potato and cassava, or legumes like peas and lentils are used instead. Legumes are high in fibre and can provide a useful source of protein in addition to carbohydrate. However, starchy vegetables tend to be lower in fibre and other nutrients, and are more expensive than grains.
Different for dogs?
The anti-grain brigade is quick to argue that dogs and cats are carnivores – they hunt for meat, not wheat. Some are willing to concede that while dogs are omnivores – they can eat meat, grains, vegetables, fruits, discarded pizza crusts, kids' birthday cakes including candles... pretty much anything really – cats are 'obligate carnivores' that can't digest grains and have to eat meat.
The anti-grainers counter-argue that dogs are descended from carnivorous wolves and share 99.8% of their DNA and therefore must be fed as carnivores. However, the small number of genes in which wolves and dogs differ include a group related to the digestion of starch – and these genetic adaptations formed an important step in the early domestication of the dog. Grains are relatively cheap, and they're a source of protein, vitamins, minerals and fibre, so can play a valuable role in the diet of a dog.
Cats are a different story. A small study that allowed cats to choose from foods with varying levels of carbohydrate, protein and fat found the ideal balance was 52% of energy from protein, 36% from fat and only 13% from carbohydrate – a similar balance to eating a rat! But in most dried foods at least 30% of energy is supplied by carbohydrate, and only 30–40% from protein. Wet food is usually lower in carbohydrate, and may consist of just meat products, gelling agent and added nutrients.
So the question for cats is more about whether they should be eating large amounts of carbohydrate, rather than if they should eat grains specifically.
Fat cats and portly pups
One concern is that a high carbohydrate diet may increase the risk of diabetes, and while some studies have found this not to be the case, a recent (2017) large Swedish study found cats with type 2 diabetes were more likely to have been fed a mostly dry diet. However, it's not certain whether it's because of the carbohydrate in dry food, or some other factor. Other researchers, for example, found that adding water to dry food made cats more active and eat less, and we know that inactivity and overweight are associated with diabetes.
Limited research means there's no good evidence that dogs and cats on the whole do better on a grain-free diet, and no evidence a diet with grains does harm on the whole. In the many decades since the advent of prepared pet foods that contain grains, pets have been living long and healthy lives. By the same token, grain-free foods can be healthy, as long as they're from a reputable company.
There will be some dogs that benefit from a reduced grain or reduced carbohydrate diet – skin problems and gastrointestinal upsets may be solved with a different diet.
In general, the far greater risk to pet health is obesity, which can come from eating too much of anything.
From a sustainability perspective, plant foods are more environmentally friendly than meat products.
Living a gluten-free lifestyle? Now your pet can too, with a variety of dog and cat foods claiming to be gluten-free. As with humans, there's no evidence gluten is harmful for most animals – the main exception seems to be some Irish setters, which are susceptible to coeliac disease. If you suspect a genuine intolerance, see your vet about undertaking a proper food intolerance test for your pet.
There's limited data on the incidence of food allergies in dogs and cats, but they're uncommon in dogs and rare in cats. Symptoms are mainly skin-related (itching, redness, sores, hair loss) and gastrointestinal (vomiting, diarrhoea). Studies report the most common allergens in dogs are beef, dairy, chicken and wheat, while for cats it's beef, dairy, fish and lamb. The only way to confirm an allergy is to go on an elimination diet, supervised by a vet, and then reintroduce suspect foods to test for reaction.
Meats are the main allergens, but it can be difficult to find food from single animal protein sources – a commercial food labelled "Lamb dinner" could also contain chicken, beef, pork and other meats. Checking the label carefully is important. However, a 2015 UK study of animal DNA in pet food found animal species that weren't listed on the label, while a 2013 Italian study discovered unlabelled animal species even in special hypoallergenic diets.
When a product states it's "hypoallergenic", it's important to check what allergy is assumed – and therefore what's absent from the product. For example, the range of Ivory Coat Natural Health Hypoallergenic products include potentially allergenic meats such as chicken and fish, so if your pet is allergic to chicken or fish these products won't be hypoallergenic for them, but other varieties may be. The Royal Canin Hypoallergenic food, on the other hand, contains hydrolysed proteins specifically designed for vet-supervised allergy diets.
Some products claim to have "human-grade" ingredients, though technically once a food has left the human food supply chain, it is no longer "human-grade". It's usually meant to imply the ingredients are good enough for human consumption, such as meat in the form of muscle meat, rather than by-products, as well as various plant products and fats such as fish oil.
But are the much-maligned by-products so bad? While there's no definition for by-products in the Australian pet food standard, the definition supplied by the Association of American Feed Control Officials (AAFCO) states it "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. It does not include hair, horns, teeth and hoofs". In other words, it's the parts of an animal that a carnivore would normally eat, but are less popular with humans – though this varies by culture.
From an environmental and animal welfare point of view, making pet food from the nutritious 'leftovers' of animals slaughtered for human meat consumption makes use of what would otherwise be a waste product to be disposed of, and prevents the need to raise and slaughter yet more animals.
The ingredient lists of some pet foods wouldn't look out of place on a wellness blogger's shopping list: kale, sea kelp, blueberries, cranberries, carrots, sun-cured alfalfa, emu oil, flaxseeds, salmon oil, green-lipped mussels, yoghurt, chicory root, dandelion and yes, even coconut oil!
Ingredients that sound good to humans may in fact be less beneficial than ingredients that don't sound as good, and could just be a cynical attempt to justify the high cost of the food. As Adelaide vet Dr Andrew Spanner says, "Pets don't have wallets, people do. Marketers target pet owners by making foods that sound good and look good."
For many of these ingredients, there's no evidence they provide any benefit to your pet. Furthermore, some ingredients (the fruit and herbs, rather than the oils) are likely to be present in such small quantities as to be inconsequential, even if they did have a benefit. Too much of any fat, whether coconut oil, fish oil, emu oil or any other fat, can be dangerous, leading to pancreatitis.
There's a zoo in the pet food aisle! Bison, venison, wild boar, duck, emu and kangaroo are now found among the more commonplace beef, lamb and chicken. But these more exotic sources of meat offer no benefits over regular domesticated animals, and you may simply be paying for bragging rights.
On the other hand, if your pet develops an allergy to common meats, these more unusual variants could come in handy as a source of 'novel' protein that your pet hasn't had the chance to develop an allergy to – as long as they really are novel and you haven't already been feeding them to them. There may also be quality control and supply issues, which could affect safety, cost and availability.
Is it complete and balanced?
Some premium pet food products may not contain all the nutrients required for good health.
Foods labelled "complete" are designed to provide a balanced diet for your dog or cat, and claim to meet the recommended nutritive requirements outlined by AAFCO. Foods that don't meet the minimum AAFCO guidelines should be labelled "intended for occasional or supplemental feeding", and should be fed alongside a complete food. You'll also see words like "treat" or "snack".
Buying complete cat food, especially wet food, is a minefield for the uninitiated. Only two of these similarly packaged tuna foods (pictured) are complete: Fancy Feast's Classic and A La Carte recipes (the more expensive Royale is not). The Coles Complete Cuisine is, in fact, not complete, and as for Gourmet Delight, there's no information on the tin.
What about raw food?
A diet of raw foods including meat, other animal parts (ground bones, offal), eggs, fruit, vegetables and fats seems very natural and logical – after all, wolves and lions don't cook. There are some commercially available raw foods, or people can make their own. Fans swear their pets do well on it, though this is anecdotal – scientific evidence that it's any better for your pet than other forms of food is lacking.
Raw diets have come under some criticism, in particular from a human safety perspective – raw meats may contain pathogens dangerous to humans, with potential contamination from feeding areas and contact with the animal or their faeces.
Homemade raw diets may be lacking in certain nutrients (for example vitamin D) and some nutrients need to be in balance (for example calcium and phosphorus), so diets have to be put together carefully. There are recipes available, but nutritional analysis has found many recipes don't provide for the nutritional needs of the dog or cat.
Does premium offer any benefits over regular?
A lack of quality research on the benefits of premium pet foods means it's difficult to say with any certainty that they're worth paying extra for – or that they're not worth paying the extra.
Vet Dr Andrew Spanner is frustrated by the paucity of scientific evidence on the pros or cons of different pet foods, with much of the reporting based on anecdotes.
He told us that when he first started practising as a vet, he was sceptical about the benefits of premium foods, and students who come through his practice now are also sceptical – despite the controversial presence of pet food company funding and promotion at university vet schools.
Over time, however, he became more and more convinced that premium diets were better, in particular if pets had skin conditions or gastrointestinal illnesses that didn't seem to go away.
"But for most healthy pets," he says, "owners will struggle to notice any difference. The biggest difference is in faecal volume – premium food will mean firmer stools and less of it. That said, if you asked vets what they feed their own pets, probably most would feed premium foods."
Differences in brands
Dr Spanner cautions that some premium food companies are better than others, and quality control plays an important role in the grade of the final product.
"The size of the larger companies allows them to perform frequent batch testing and feeding trials. A good question to the smaller companies would be whether they're able to match this kind of quality control."
The World Small Animal Veterinary Association recommends that you choose a pet food from a company that can provide a contact number for enquiries about its products. This way, you can call to check that the food has been developed with a nutritionist and tested using feeding trials to make sure pets can digest it properly.
This information is readily available on the websites of the biggest companies: Mars (Advance, Royal Canin, Iams, Optimum, Eukanuba), Purina (Pro Plan, Fancy Feast) and Hills. We contacted several smaller premium pet food companies about their nutritional advisers and feeding trials. Applaws, Ziwi and Meals for Mutts ticked all the boxes, while Ivory Coat requested more time to respond. VIP Petfoods, Taste of the Wild and Black Hawk didn't respond.
People often argue that premium foods may cost more than regular food, but you end up feeding less so it's not so much more. We compared the cost of various regular and premium dry dog foods (cat food was covered in our 2016 tests) based on recommended serving size. Serving size, and therefore cost, will vary according to the size of the dog, among other factors. But for comparative purposes, we used a 10kg dog, where the cost ranged from around 50 cents to $5.50 per day.
However, the amount of protein and the energy provided each day were also very different from product to product, making it difficult to do a direct comparison in terms of nutrition. Plus, the amount of food you need to feed your pet may vary from the recommended amount, depending on your pet's level of activity and other factors.
We found the recommended serving sizes for many products would not provide enough energy for a typical dog's weight maintenance, and would need to be increased – which would also increase the cost per day. For a typically active 10kg desexed dog, the recommended intake is between 470-630 kilocalories. So we also calculated the cost based on feeding enough to meet the recommended daily energy intake (550 kilocalories).
Premium dry dog food cost and nutrition comparison
|| Price ($)
| % Protein
|| % Fat
| Pedigree Adult with mince and veggies*
| Purina Supercoat*
| Advance Total Wellbeing All-breed lamb and rice
|Applaws It's All Good Grain-Free Chicken and Turkey
| Big Dog Raw Beef
| Black Hawk Grain-Free Lamb Adult
| Black Hawk Lamb and Rice Adult
| Ivory Coat Lamb and Kangaroo
| K9 Natural Lamb Feast
| Meals for Mutts Kangaroo and Lamb
| Optimum Chicken Vegetables and Rice Adult
| Purina Grain-Free Supercoat
|Taste of the Wild Bison & Venison
| VIP Nature's Goodness Grain-Free (dry)
| Ziwi Peak NZ Beef
* Non-premium products
- Costs are based on recommended retail price in July 2017. Unit cost may vary according to pack size.
- The recommended daily protein intake for a 10kg dog is 20 grams.
- Recommended daily calorie intake range is based on a 'typical' activity, neutered 10kg dog. Serving sizes providing energy outside this range may need to be increased or decreased, which will also affect cost per serve.
- Protein, fat and calories are based on food as packaged. Big Dog raw food has a higher water content than the other foods, so figures look lower per 100g.
There's not enough definitive information to say whether premium foods are any better for your pet than a regular food. If your pet is healthy and happy, you may not notice any difference, though your wallet may be lighter. But anecdotally, some pets will do better on a premium diet – this is something to discuss with your vet.
When it comes to food, the biggest health problem facing pets today is eating too much of it. Obesity affects about half of Australian pets, with consequences far greater than any arising from too much grain, too little superfood or the use of meat by-products.