In part one of the raw meat-based diet series, I investigated and explained a few myths associated with raw meat-based diets, this was predominantly focusing on dogs. In part two of the series, I was asked is raw food ‘best’ for dogs, now we look at the question – is raw best for cats?
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As with dogs I am going to burst that bubble and say that I truly do not believe anyone should claim there is a ‘best’ food. Every cat and situation are individual and so are their nutritional needs, what suits one cat may not suit another. So, as per the last article where I dispelled some common raw food myths used to create a negative commentary around commercial dry/ wet diets, this article also does not aim to tell you what is ‘the best’ in pet food. It does aim to use evidence to ensure owners who are thinking about, or do feed, a raw meat-based diet do so while taking all considerations into account including the evidence for its benefits, and the potential, but sometimes very serious, disadvantages.
No food choice is the ‘best’; all feeding choices have pros and cons. The reason many veterinary surgeons do not advise raw is because of the wider implication of the diet on the health of the patient; but also those coming into contact with them.
In this article we aim to investigate the claim that raw is ‘best’ so owners can understand the evidence, or lack of, behind feeding raw.
Cats are carnivores
Like all cats, the domestic cat is a carnivore. This means they are primarily a meat eater and are well adapted to a hunting lifestyle. However, unlike dogs (who were domesticated many tens of thousands of years ago and have changed from their ancestors in both genotype and phenotype), cats became domesticated only in relatively recent history. Therefore they retain many similarities with wild felines. Felis catus, the domestic cat, is one of the most recently evolved species within the Felidae family.
Genetic analysis has demonstrated that the DNA of modern-day domestic cats throughout the world is almost identical to that of the ancestral wildcat, Felis sylvestris lybica. However, this process should not be regarded as ‘domestication’ in the same way that dogs have been domesticated. In general, cats have not undergone major changes during domestication and their form, anatomy and behaviour remain very similar to that of their wildcat ancestors.
As they have naturally evolved, cas have become dependent on a meat protein diet and cannot survive without it in their diet. This means that cats are obligate carnivores; they need animal proteins in their diet for their body to function correctly. There are some essential nutrients found in meat that cats cannot synthesise or ‘make’ themselves. This may not necessarily mean that cats must eat raw meat to achieve this aim, however, so let’s look further.
What can’t Cats make?
Cats lack the ability to synthesise (make) a number of important nutrients. This is due to a complete deletion or severe limitation of the enzyme or pathway that makes each nutrient. Important examples include taurine, arginine, and Vitamin A, but there are others.
Protein
Proteins are large complex molecules consisting of chains of smaller ‘building blocks’, these are called amino acids. These are essential for the cat for many different biological processes.
However, while humans and dogs can adapt to diets that have a relatively low protein content, for example plant-based diets, cats have a much higher protein requirement in their diet that would typically only be met by feeding a meat-based (or, in theory, a chemically supplemented plant-based) diet, because they have come to rely on protein as an energy source.
In addition to requiring a much higher level of protein in the diet, cats also require a number of specific amino acids to be present:
- Taurine
- Arginine
- Methionine
- Cysteine
So, meat in a cat’s diet is important
This inability to make specific amino acids makes meat important in a cat’s diet. Many animals (including dogs and humans) can convert and use other amino acids derived from plants for at least some of these. But cats have lost the ability to synthesise these amino acids. As mentioned above the pathways have been lost or depleted because their natural diet (animal flesh and meat) contains these amino acids in abundance. These amino acids may not be found in plants, or the cat cannot use the plants to ‘make’ them. Without these amino acids in the diet, cats become very sick and ultimately it can be fatal.
What about Taurine?
Dogs and cats exclusively use taurine to conjugate bile acids which have a number of important functions. Dogs can make at least some of their own taurine to meet their needs, if their food contains adequate amounts of sulphur-containing amino acids.
In cats, the ability to synthesise taurine is so limited it is insufficient to compensate for the natural losses in the gastrointestinal tract. Therefore, taurine is an essential nutrient for cats.
Taurine deficiency can lead to:
- Feline central retinal degeneration and blindness
- Dilated cardiomyopathy and heart failure
- Reproductive failure
- And more…
How does this relate to meat and cat food?
Taurine is not degraded by enzymes in the cats’ body; but is excreted in the urine or via the gastrointestinal tract. However, some studies have indicated that taurine can be degraded by the intestinal microflora.
So, taurine is important, but the level of it can differ between foods and still be safe. The composition of the cat food, as well as the type of production process influence this intestinal degradation. Heat-processed cat foods resulted in lower taurine plasma levels and greater losses compared to frozen-preserved. For this reason, the recommendation for taurine inclusion in canned cat food is higher than that for dry food or purified diets.
Individual companies can have different levels of taurine in their products; as long as they ensure that the products maintain adequate blood value in the cat’s body. They can ensure this through feeding trials. So raw or not, taurine levels can be maintained at adequate levels. And as an extra safety net using a company who has followed up their formulations using feeding trials can help ensure that taurine remains at certain levels in cats after feeding their diet formulation.
Are Carbohydrates bad if they need high meat content?
Although obligate carnivores, cats can digest and use carbohydrates. However, cats have a slightly reduced ability to digest and utilise carbohydrates. This is because a carnivorous diet is naturally relatively low in carbohydrates.
In contrast to many other animals, cats will derive most of their blood sugar, and therefore their energy, from the breakdown of protein in the diet rather than carbohydrates.
So, are carbs bad?
The cat’s “native” diet is inherently low in carbohydrates; consisting mainly of whatever is found in the gut contents of their prey such as rodents. As such, even very low carbohydrate diets can be safely fed to many cats of all life stages. However, this does not mean that cats cannot use carbohydrates or that they should not be present in the diet.
Pros of a raw food diet in cats
Anecdotal benefits for the diet include improvement in coat and skin; elimination of breath, body, and faecal odour; improvement in energy, behaviour, and immunity; and a reduction in medical conditions including allergies, arthritis, pancreatitis, dental disease, and parasitism; these potential health benefits have not undergone thorough scientific evaluation yet.
The WSAVA states that there is no evidence that raw meat-based diets provide health benefits over commercial or balanced homemade cooked diets.
As with dogs’ digestibility or raw meat for cats is a common benefit stated by proponents of raw food feeding is in reference to digestibility and bioavailability of raw feeding. Studies have documented high digestibility of raw meat diets fed to exotic and domestic carnivores. Kittens raised on a rabbit-based raw diet also had better stool quality, assessed with a visual grading system, than their commercial diet-fed peers, but both groups grew normally and at a similar rate.
Negatives of a raw food diet in cats
Zoonoses (infections that can spread from animal to human)
Microbial contamination, by either bacteria or viruses, is the most frequently documented disadvantage of raw feeding. Specifically, Salmonella has received the most attention; however, other pathogenic bacterial contaminants include Escherichia coli, Listeria, Clostridium, and Campylobacter species. Other worrying contaminants include tuberculosis infections in cats.
Pathogenic bacterial contaminants in raw meat and poultry products sold for human consumption varies greatly. Overall, a prevalence of 10 to 20% is reported for raw human edible products being contaminated with Campylobacter, Escherichia coli or Salmonella species. Just because a food claims to be ‘human grade’ does not make it safe. Nor does it mean that much because meat used in animal food cannot be meat that has been removed from the human food chain because of disease etc.
Gut bacteria
Of the primary gut bacteria, Salmonella spp. is found in the feline intestinal tract. And yet salmonellosis is uncommon in healthy cats, being seen more in cats that are immunosuppressed. The frequency of faecal shedding of Salmonella by dogs fed raw diets correlates with the Salmonella risk of the food material in many studies but we don’t appear to have a huge amount of evidence for shedding in domestic cats. Salmonella prevalence among cats is variable with shedding rates from 0-14%. However, higher prevalence rates are found in cats fed with raw food diets with the odds of shedding Salmonella estimated to be 23 times greater for dogs fed with raw food diets than those given commercial diets.
Multi-resistant (to antibiotics) epidemic Salmonella serovars that are not currently present in UK food animals pose a risk of the subsequent incursion of such resistant strains into British poultry flocks via pet cats (and dogs) shedding the organisms. Furthermore, two studies reported associations between raw meat-based diets and faecal carriage of E. coli in cats. Another found E. coli isolated from raw cat pet food and from faeces of cats fed raw meat-based diets was a common clinical isolate seen increasingly in human cases in Europe.
Viruses and immune function
Worryingly, there have also recently been reports of Avian Influenza being spread to cats through consumption of infected birds.
Another frequently cited benefit when feeding raw meat-based diets is an improvement in immune function. In experiments conducted by one of the authors, domestic cats fed a raw diet for 10 weeks had a significant increase in lymphocyte and immunoglobulin production, whereas there were no significant changes over the study period for cats fed a cooked commercial moist diet. In those experiments, it was also found that cats fed the raw meat-based diet were faecal shedders of Salmonella spp. This increase of lymphocyte and immunoglobulin production does not necessarily mean that these cats have superior immune function. But perhaps more likely that they are having to work harder to keep microbes at bay. More evidence is required in this area.
Parasites and Protozoa
Parasites are a risk for raw meat-based diets in both cats and dogs, there are steps we can take to help mitigate the risk of parasites in raw food. Studies have shown that adequate freezing at the right temperature and for the right amount of time can remove most parasitic risks. It has been suggested that the ideal freezing time is a minimum of −18°C for 10 days. Cats who are avid hunters are also at risk. With Toxoplasma gondii, there is an established zoonotic risk from infected cats; raw-fed cats have been shown to demonstrate increased toxoplasma rates and oocyst shedding. Toxoplasmosis can be passed from cats to humans through exposure to oocysts in the cats’ faeces and the consumption of raw meat significantly increases the likelihood of a cat being exposed to and developing antibodies to T gondii.
What to look for in a good ‘brand’ of food
We do know however, that there are some commercial foods, whether wet, dry, cooked or raw, whose formulations are more likely to be good quality because the companies use veterinary nutritionists (PhD or Board Certified), feeding trials and evidence to back up their choice of formulations, feeding trails are massively important to understand who formulations work in ‘real life’ circumstances. Some formulations, that may appear to be complete and balanced on paper, when applied to living animals, can often begin to fall short.
If you think that home formulation is best, be careful. The vast majority of home prepared diets, whether cooked or raw, fail to meet nutritional standards. This is why it is essential to use a board-certified veterinary nutritionist to guide your recipes if you choose to home prepare. Interestingly a study into homemade diets in dogs found them to be rarely balanced leading veterinary professionals to worry about the short and long-term implications this diet may have on companion animals’ health. Although ‘home-made’ doesn’t necessarily correlate with ‘raw feeding’ as there are commercial brands available, a percentage of raw feeders do make their own formulations at home. So using a board-certified veterinary nutritionist to support you is essential.
Conclusion
There is lots to weigh up when choosing a cat’s diet. But raw is certainly not ‘best’ in many circumstances; particularly if the cat is coming into contact with children or immunocompromised individuals. By picking a company we can trust to have formulated well, and given thought to adequate freezing, storage, testing and transport we can mitigate but not eliminate all these risks.
So, there is no ‘best’ diet for cats because every situation is unique. But there are certainly some serious considerations to consider when picking a good quality diet for our cats.
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