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I Refuse to Feed Kibble : A Vet’s Perspective

I Refuse to Feed Kibble : A Vet’s Perspective

Author Dr Nick Thompson, The Holistic Vet

Rendering, Extrusion & Advanced Glycation End Products.

Don’t know what these terms mean? Read on and in 5 minutes, you will, and you will be glad for the health of your canine pal you did!

I could regale you with twenty reasons I turn my back on kibble for pets. I won’t bore you. Just trust me – if you feed ultra-processed food (yes, there is such a thing!), you are likely to induce diseases in your pets.

Obesity, for example, 65% of dogs in the UK and USA are overweight or obese. The British Small Animal Veterinary Association now defines obesity as a disease. They state that obese animals are not only more expensive to keep through their lifetime but can die up to two years before similarly aged trim buddies. 

High carb, ultra-processed kibbles raise blood glucose levels and, as such, induces long term insulin excess. Insulin increases nutrient storage (as fat). In wild animals, it’s the hormone of the autumn that animals rely on to put on fat to get them through food shortage in winter. 

I could go on to the other 19 reasons I can think of to avoid kibble, but I won’t. Today I’d like to look at the three REALLY evil bogeymen in modern kibble nutrition: 

  • Rendering carcass to produce meat and bone meal,
  • The kibble production process is called extrusion and the damage it does to food.
  • Glycation end products (AGEs – carcinogenic by-products of high-heat processing in rendering and extrusion).



If you read the websites of meat and bone meal producers, they say positive things about rendering, such as: 

“The Integrated Sterilizer and Shredder gives a full medical sterilisation cycle with steam at low temperature (121 °C) to keep the animal by-product protein content of the load. It secures the quality of the end-product, and while neutralises bacteria and viruses, it shreds the loaded material into pieces within a pressure vessel”.

This particular site goes on to say: 

“The feeding of by-products and the discharge of end-products are performed automatically. The materials (solid – meat meal, bone meal, blood meal, feathers meal-, water and oil) are collected in separate containers for easy access and discharge.

After the animal waste recycling treatment in the ISS, the processed animal by-products are rendered non-infectious, non-hazardous, and are sterile from bacteria, viruses and prions”.

Rendering is the process by which everything from dead food animals is recycled.  I think recycling everything from dead food animals is a great thing. It’s essential for the sustainability of farming, but what’s terrifying is this stuff is fed back to cattle, sheep, pigs and our pets? 

Prepare yourselves, here comes the factual account of rendering:

In concentrated beef animal feed operations in the USA, chicken and beef meat and bone meal are fed to growing animals to increase protein intake. It’s just wrong to make these animals cannibalise each other, but that’s another story. Read The Omnivores Dilemma by Michael Pollan if you want the full horror of this practice in the USA. 

Rendering is an excellent way to remove all vitality and nutrients in the meats at the beginning of the process. 

That in itself is bad enough, but in reality (and you might want to sit down to read this), in busy rendering plants, plastic bags containing heads and viscera, nylon string and plastic ear tags also go into the mix. So these toxic plastic materials are powdered into the meat meal that goes to your pet’s kibble factory. Yummy. 

Don’t believe me? Ask your kibble manufacturer where they source their meat and bone meal and whether they can guarantee it is free of trace quantities of plastics. 

You may have noticed that the renderers text mentions feather meal. Feather meal? Are you serious? I’m afraid I’m deadly serious (pun intended). Here’s the ingredients list of Royal Canin’s Anallergenic kibbled food. I’ve underlined the ‘interesting’ ingredients: 

Composition: Maize starch, feather hydrolysate with low molecular weight (source of L amino acids and oligopeptides), copra oil, soya oil, minerals, vegetable fibres, chicory pulp, fructo-oligo-saccharides, fish oil, mono – and diglycerides of palmitic and stearic acids esterified with citric acid, animal fat, marigold extract (source of lutein). Protein source: feather hydrolysate with low molecular weight. Carbohydrate source: maize starch.

On we go with our grim analysis. Next – extrusion. 


Extrusion is yet another step in the kibble production process. You can’t get a simpler or more concise description of the rendering and extrusion process than in Amy Marshall’s fantastic book, ‘Why You Need to Feed Your Dog a Raw Food Diet’. This is a direct quote from it. Thanks, Amy! 

‘Kibble opponents argue that roughly half the nutrition is baked out of your dog’s food every time it’s heated. When ingredients are heated five or six times throughout the entire process, it’s safe to assume what nutrients may have been present in the food are now lost’.

 She goes on to describe the process in full:

  1. Rendering – raw animal material or “protein” is processed at least once, possibly twice. It’s cooked at temperatures hovering around 280 degrees, often for hours at a time. 
  2. Hammer Mill – Dry ingredients including meat and bone meal are ground into a flour-like powder. Animals, meat and bone have been heated, melted, and processed so intensely that they are now in the form of flour. 
  3. Preconditioning – Hot water and pressurised steam cook the ingredients. 
  4. Extruder – Tube walls reaching extremely high temperatures cook ingredients as they’re pushed through the steel cylinder. 
  5. Enrobing Round One– After kibble is sliced from the die, it goes into a heated oven to dry and harden. 
  6. Enrobing Round Two – After being sprayed with other liquids and powers, the kibble goes back into the heated oven for the final phase of drying and hardening. 

Yes – systems like this account for the majority of pet kibble. The bulk of the 825,000 tonnes of dog food sold in the UK in 2018 was kibble – made using these extreme processes. 

(statistics from


Advanced Glycation End Products (AGEs)

AGEs are aptly named because they are significant drivers of the degenerative process we call ageing, getting old and sick. AGEs are made in the body, especially in the presence of high blood glucose (see above for the link between kibble and long term excess blood glucose). Sticky glucose sticks to body proteins, denaturing and ‘ageing’ them. 

In food processing, too, glucose (from starch breakdown from cereals and sweet potato etc.) clings to food proteins, this time because of high temperatures. This damages the delicate proteins, rendering them useless and toxic to pets eating the resulting kibble.

Think of pouring golden syrup into your laptop keyboard and see how you get on! 

Kibble defenders argue that AGEs are only present in small quantities. I would say to them that they’re also present in small quantities in cigarette smoke – would they consider cigarettes harmless, too? 


  • Rendering damages food and adds plastic particles. 
  • Extrusion nullifies any goodness left in meat and bone meal after rendering. 
  • Both produce toxic, ageing AGEs.  

Kibble, anyone?  

And these are just three reasons I don’t feed kibble!  I have another 17, but I will save those for another blog. 

If this article has highlighted practices you weren’t aware of before, and you are a kibble feeder asking what DO I feed my dog then? My answer is a raw dog food or fresh wholefood diet, formulated with minimal processing, as close to its natural form as possible. Explore our full grain free dog food range.


Dr Nick Thompson

BSc (Hons) Path Sci., BVM&S, VetMFHom, MRCVS. Founding President of the Raw Feeding Veterinary Society. Petplan Vet of the Year Nominee 2009, 2015, 2017, 2018 & 2020. The practice of the Year Nominee 2018.


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