Cats and dogs are not human, nor are they tigers or wolves. Unfortunately, the latest feeding trends – raw, prey, grain-free and so on – seem to be based on the premise that the cats and dogs we live with are anything but domesticated pets.
Cats and dogs require nutrients, namely: protein, lipids, vitamins and minerals. These nutrients are required in varying, specific quantities which differ between species and at different life stages.
A good analogy when explaining nutrition to pet owners is to think of a delivery van as an ingredient and a package as a nutrient – as long as the package arrives in good condition and it’s what was ordered, one doesn’t usually mind who delivered it!
We can get good, high quality nutrients from a number of different ingredient sources. More importantly, we must remember that most ingredients provide more than one nutrient and that nutrients interact with each other. Consequently, trying to balance a diet without a PhD in animal nutrition is nigh on impossible.
| Essential Amino Acids | Non-Essential Amino Acids |
|---|---|
| Arginine Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine Taurine (cats only) | Alanine Asparagine Aspartate Cysteine Glutamate Glutamine Glycine Hydroxylysine Hydroxyproline Proline Serine Tyrosine |
Protein, amino acids and lipids
If we look at nutrient requirements scientifically, we can break it down further; what our pets really need are amino acids: 10 essential for a dog, 11 for a cat (see Table 1). These are vital for many processes, including cognitive function, reproduction, vision and growth. Deficiencies of any of these essential amino acids can have catastrophic consequences. For example, cats can quickly become critically, and even fatally, ill, from eating a diet that is deficient in arginine.
Marketing a pet food using a list of amino acids isn’t very appealing or understandable to most pet owners; using anthropomorphic phrases, such as “packed with fresh chicken” or “delicious human grade meat”, is much more appealing. The fact that human grade meat must be used by law, that fresh chicken is around 75 percent water or that the word “meat” gives no indication of quality, digestibility or amino acid profile is generally not known nor easily understood.
Certain vegetable sources, such as corn, wheat and soy, when processed properly, can be highly digestible protein sources and in combination with by-products from the human food chain, such as offal, can provide palatable, balanced and sustainable foods that provide all the nutrition – including the essential amino acids – that a pet needs. Lipids are essential for the utilisation of vitamins A, D, E and K but are also an excellent source of energy.
Vitamins and minerals
The potential dangers of over- or under-supplementation of vitamins and minerals is so great that all prepared pet foods (even “natural” ones) must contain synthetic vitamins and minerals, making 100 percent of “natural” foods unnatural. This is done, of course, for sound, scientific safety reasons – one example of serious excesses would be hypervitaminosis A, seen in cats fed excessive quantities of raw liver. Deficiencies can also cause serious health issues, such as cases of nutritional secondary hyperparathyroidism due to calcium deficiency.
Unfortunately, most home-made diets for cats and dogs are not balanced. In fact, studies of almost 300 different recipes found that all but 5 percent were deficient in at least one nutrient and around 60 percent profoundly deficient in many nutrients (Dilitzer et al., 2011; Stockman et al., 2013).
Carbohydrates
Carbohydrate is a broad term covering starches, fibre and sugars. While carbohydrate is not an essential nutrient for a dog or cat, when used strategically, it can be very useful. For example, specific starches improve faecal quality and carbs are a great energy provider, allowing protein to be spared for other biological uses and, practically, it is essential to bind kibble together.
Specific fibre blends can be used to improve gastrointestinal health, encouraging the proliferation of healthy gut microbiota, including in cats, and to provide a satietogenic effect in pets prone to weight gain.
Despite all the proven benefits of carbohydrates, cynicism persists. Around 7,000 years ago, the digestive systems of some wolves evolved to produce amylase in order to digest starch. This was necessary for them to cohabit with us and eat what we ate. A dog’s role would have been guarding livestock, which would primarily have been used for sustainable benefits such as wool and milk, with only occasional meals of meat for both humans and dogs.
The debate around carbohydrates in cats and the definition of “obligate carnivore” rages on. While it is important that cats are not fed vegetarian or vegan diets, it is their dentition that defines their carnivorous status. In the wild, they would eat carbohydrates from the intestines of their prey. An all-meat diet is not healthy for cats, as evidenced by veterinary nutritionist Catherine Lenox in 2015, who treated a five-month-old kitten fed an all-meat diet since weaning, which presented with both retinal degeneration and metabolic bone disease as a result of taurine deficiency. Table 2 shows some important differences between the species; it is notable that there is no salivary amylase in cats and dogs. Nevertheless, they are very adept at digesting carbohydrates.
| Human | Cat | Dog | |
|---|---|---|---|
| Taste buds | 9,000 | 500 | 1,700 |
| Olfactory cells | 2 to 10 million | 80 to 90 million | 80 to 220 million+ |
| Digestive tract as a % of body weight | 11% | 2.3% | 2.7 to 7% |
| Salivary amylase | yes | no | no |
Choosing a diet
The three most important questions to consider when choosing what to feed a pet are: Is it safe? Is it nutritious? And is it right for this pet?
Food safety should be the first priority, particularly when feeding raw foods. Recent papers show that the risk to human health, particularly the elderly or immunocompromised, is significant. A discussion about hygiene is vitally important when debating what to feed a pet – traditional, dry, raw, grain-free or otherwise.
Considering whether a diet is completely balanced or complementary is important too – and if it is complementary, it should be considered a treat, make up no more than 10 percent of the diet and be mixed with a fully balanced and complete diet.
Different pets have different needs and certain factors drastically affect nutritional requirements. For instance, neutering reduces energy requirements in both cats and dogs. Adapted levels of protein, calcium and phosphorus are needed in growth and large dog breeds have different nutritional requirements to small breeds.
Finally, indisputable scientific evidence tells us that dogs and cats are living longer (dogs by 4 percent and cats by 10 percent according to a 2013 report by Banfield Hospitals) and although in part this is due to better veterinary care, it must also be due to better nutrition and a better understanding of the complexities of dogs’ and cats’ nutritional needs.
Within a profession which prides itself on making evidence-based decisions, can we afford to ignore the abundance of scientific evidence around companion animal nutrition yet embrace the current fad of home-prepared or raw feeding?
A full reference list is available on request
