Dr. Suzanne Moyes explains how we make our tasty Excel Nuggets

This is an extract from the article “Small animal food: what’s involved in creating nutritionally balanced nuggets?” By Dr. Suzanne Moyes, published in the Vet Times in 2022.

Ever thought how we make our tasty Excel Nuggets? Dr. Suzanne Moyes, Deputy Managing Director and in-house vet at Burgess Pet Care explains the extrusion process as well as the benefits for small animals below.

“First and foremost, we cannot underestimate the importance of fresh grass or high-quality feeding hay in a fibrevore’s diet. In addition to being the primary source of fibre – which is essential for digestive health – grass and hay also provide other important health benefits.

These benefits include supporting dental health, by wearing down constantly growing teeth, and emotional health, by allowing natural foraging behaviour. These are the reasons why 85% to 90% of a fibrevore’s diet should be fresh grass or feeding hay.

Given the natural variability in the levels of nutrients other than fibre, concentrated feed – in the form of nuggets – has an important supporting role in ensuring a balanced diet by supplying a controlled level of macronutrients and micronutrients. For rabbits, guinea pigs and other fibrevores, single-component nuggets should make up 5% of the diet.

Following on from research carried out by The University of Edinburgh, which highlighted the risks associated with feeding muesli-style diets, Burgess no longer manufactures muesli diets for any species. We believe that, given the strong biological drive to consume energy, all small animal species will selectively feed if given the opportunity. For that reason, we only make single-component nuggets.

When it comes to creating top-quality nuggets for small animals, it is essential to ensure the right balance of nutrients. While that sounds relatively straightforward, putting it into practice is actually quite tricky.

While extruded nuggets are widely acknowledged as the best way to support a forage-based, balanced diet for rabbits, guinea pigs, chinchillas and other fibrevores – as opposed to muesli-based diets, which may encourage selective feeding, increasing the risk of several health issues – creating those tasty little bullets of nutrition takes a high level of skill, knowledge and expertise. So, if you have ever wondered exactly what is involved, you will find all the answers here…

First up, I will explain how the thermal extrusion process works, and the benefits it brings to creating nutritionally balanced, highly digestible and safe food for small animals. Next, I will take a closer look at the wide range of nutritious and tasty ingredients we use in our recipes – and explain why we choose them. Finally, I will run through the vitamins and minerals we add to the mix to ensure each species of small animal gets the correct amount they need.

I will also explain how we keep those vital vitamins intact during the thermal extrusion process and throughout the shelf life of the finished product, ensuring small pets get the best nutrition possible.

The nugget-making process

Single-component small animal food can be made via two manufacturing processes:

• cold-pressed pelleting
• thermal extrusion

Cold-pressed pellets (sometimes called nutri-pressed pellets) are made at lower temperatures using high pressure to bind the ingredients together. In comparison, nuggets made via thermal extrusion are cooked at higher temperatures.

At Burgess, all our nuggets are made at our own factory in the heart of Yorkshire using thermal extrusion. The process involves grinding down a range of ingredients into a fine flour and mixing them together. We add steam and water to create a soft mixture that can be pushed through an extruder, where it is cooked by thermal and mechanical energy, then through a die plate to form the nugget shape. The freshly pressed nuggets are then dried, cooled and packaged.

Producing nuggets via thermal extrusion has a number of benefits.

Better for digestion

Our nuggets contain whole grains, which are a source of fibre, protein and energy in the form of starch. However, starch can be difficult for small animals to digest. By using heat in our process, the starch is cooked (gelatinised). Without this cooking process, a bacterial overload may result, as the starch is rapidly fermented by the microflora present, which has the potential to cause digestive issues – particularly in very young or stressed animals.

Cooking of starch has been shown to increase its absorption in the small intestine. Internal testing showed cold-pressed pellets had a gelatinisation of around 65% whereas, for thermally extruded nuggets, this was 80% or higher.

Food safety

Many of the ingredients used in small mammal feed are minimally processed before extrusion and may have been exposed to the wild animal population. The temperatures reached during thermal extrusion are an important step in ensuring food safety.

Combating anti-nutritional factors

Using heat also reduces anti-nutritional factors in the food. Many of the ingredients used in animal food, such as soya beans, contain anti-nutritional factors – essentially components in foods that can reduce the effectiveness of some of the nutrients. These include compounds such as trypsin inhibitors, phytates, polyphenols, tannins, anticoagulants, phyto-oestrogens and other alkaloids. The temperatures reached in the thermal extrusion process destroy these compounds to ensure any risk to animal health is eliminated.

Of course, any cooking process results in the loss of some nutrients. However, these losses are outweighed by the benefits of thorough cooking – notably the reduced risk of digestive upsets and the destruction of anti-nutritional factors. The reduction in nutrients in thermal extrusion is well-researched and can be considered when formulating recipes. The formulations Burgess uses are designed to ensure our thermally extruded nuggets contain the right level of nutrients after processing.

A whole host of nutritious ingredients

Each ingredient that goes into our nuggets – ranging from grass meal and wholegrain wheat to beneficial dried herbs, such as mint and oregano, along with dried nettles and dandelions, which all make up a typical forage-based diet – comes with its own set of challenges.

---Read more about the specific ingredients we use in our Excel Nuggets in our blog post "Beneficial ingredients used in Burgess Excel: A list from A to Z and the benefits for small animals"---

For example, a significant natural variation exists in the nutrient content of forages, influenced by many factors – including the mix of plant species in the forage, time of year it is harvested and the soil the plants are grown in.

In addition, some ingredients – such as lucerne (also known as alfalfa) – have high levels of calcium that need to be tightly controlled to ensure any foods produced with it are safe for small animals. Peas – which, along with being a source of protein and energy – also contain anti-nutritional factors, but these can be destroyed during the thermal extrusion process.

The benefit of added vitamins and minerals

At Burgess, we add vitamins and minerals to our nugget recipes to ensure each species of small animal gets the correct amount they need. Importantly, these are added in specific compounds. This ensures they are not only safe and beneficial for small animals, but also remain intact during the thermal extrusion process and throughout the shelf life of the product.

And, while a deficiency of vitamins and mineral will result in health problems, it is essential that small animals do not consume excessive amounts, as this can also be bad for them. To ensure optimum safety, at Burgess we consider all the available research to ensure our foods contain the correct levels so pet owners do not need to add extra supplements to their small animals’ diet.

The vitamins and minerals we use at Burgess are tightly regulated and must be approved by the Government. Labelling regulations mean that vitamins and minerals are often classed as “additives” on our products.

92% of UK vets recommend our Burgess Excel small pets range

At Burgess, we are continuously monitoring the latest research into small animal health, nutrition and well-being, and constantly building on our extensive knowledge to expand our range of specially tailored foods.

Burgess Excel small animal nuggets are made using only the finest quality ingredients for rabbits, guinea pigs and chinchillas. The entire range is single-component nuggets to prevent selective feeding. We also offer a range of high-quality feeding hay and grass-based treats.

Burgess Pet Care has led Rabbit Awareness Week for the past 16 years and is a founding member of the Rabbit Awareness Action Group, which comprises some of the UK’s largest animal welfare organisations and charities, and has been established to ensure a greater understanding of rabbits’ health and welfare requirements.”

Read the full article on the vet times at https://www.vettimes.co.uk/article/small-animal-food-whats-involved-in-creating-nutritionally-balanced-nuggets/