Irradiated Pet Food

LAST UPDATED 13 APRIL 2023

This article is written by Pet Circle's qualified veterinarian, Dr Gillian Hill, BVSc (Hons)

Contents:
What is irradiated pet food?
Why is some pet food irradiated?
How does gamma irradiation work?
What is the evidence regarding the safety of irradiated foods?
Which pet foods are irradiated?
Is irradiated food safe for pets?
Further reading

What is irradiated pet food?

'Irradiated pet food' refers to pet food products that have been subjected to a sterilisation procedure by exposure to either electromagnetic radiation (most common - using Gamma irradiation or x-ray ionising radiation), or particle radiation (less common - using electron beam).

Irradiation has been used in the food industry in many countries to extend the shelf life of food by reducing the population of bacteria in the finished product. The option of irradiation is not available as a biosecurity import measure for food for human consumption unless supported by the Australia New Zealand Food Standards Code.

Why is some pet food irradiated?

Australia has some of the most biodiverse environments in the world. Our biosecurity policies are designed to protect these pristine environments, and keep Australia free from harmful pests, diseases and weeds.

Pet food products can pose a risk to our country as they may contain disease agents or pests that are exotic to Australia. Irradiation of pet food products is currently accepted by the Australian Department of Agriculture, Fisheries and Forestry (DAFF) as a "biosecurity treatment for a range of products of animal origin"¹, in order to address biosecurity concerns about the product. This is "especially the case where a product does not meet Australia's biosecurity requirements, the product has not been adequately processed or tested to address Australia's biosecurity concerns, or where the manufacturer is unable to provide the department with sufficient information to complete the risk assessment."¹

How does gamma irradiation work?

In the pet industry, heat treatment and irradiation are the only options for managing food safety risks. Both treatments have the potential to affect the characteristics of the food, including dose-related effects on certain nutrients, and the production of radio-lytic byproducts.

Gamma irradiation is the predominant type of irradiation used for food treatment. It is a type of electromagnetic radiation originating from either cobalt-60 or caesium-137 (cobalt-60 is the main type in use).

When cobalt-60 decays, it becomes nickel, and emits 2 high energy gamma rays which have great penetrating ability, similar to x-rays. These rays can pass through both high and low density products, including those in their final packaging.

When the gamma rays are absorbed by the food product, the atoms in the product become ionised (transformed to a charged or unstable state), and this results in the breakdown of the chemical bonds within the food. This process affects the DNA of any microorganisms within the food, rendering them non-viable. However, this process can also produce free radicals, and can result in the loss of nutrients in the food.

The macronutrients in the foods (carbohydrates, fats and proteins) have not found to be significantly affected in terms of nutrient value and digestibility by treatment with irradiation. However, some micronutrients, such as vitamins A, E and thiamine, can be particularly sensitive to irradiation, and an increase in the oxidation of the fats in animal feeds has been found where the product has been treated with a dose over 25 kilogray (kGy). Currently, the level of irradiation required for pet food products is set at 50 kGy. Because of this, irradiation as a biosecurity option is not supported by DAFF if the products are likely to make up a significant portion of an animal's diet, such as dry kibble.

It is important to note that the gamma rays are well below the threshold for photonuclear activation of any chemical element, so no radioactivity can be induced in the treated food.

What is the evidence regarding irradiated food safety?

There have been numerous studies looking into the safety of irradiated foods. Some of these are:

1959 - A study was performed on rats fed either fresh or stored beef irradiated to 2.79 megarad (equivalent to 27.9 kGy) and 5.58 megarad (equivalent to 55.8 kGy). The consumption of the irradiated diet resulted in internal bleeding and prolonged blood clotting times in growing male rats. Generally the female rat did not show this syndrome. Supplementation with vitamin K prevented the bleeding.¹⁸

1965 - The United States Army Surgeon General was given responsibility for testing irradiated food wholesomeness. They concluded that in general, irradiated foods are as acceptable as non-irradiated foods.⁶

1970 - A study was performed on rats over a 2 year period and through 3 generations. The rats were fed carrots irradiated to 2.79 megarad (equivalent to 27.9 kGy) and 5.58 megarad (equivalent to 55.8 kGy) as 35% of their total dry diet. A small but significant depression in growth rate was seen, otherwise no deleterious effects were observed. The growth depression was not observed consistently in subsequent experiments.¹⁷

1976 - The effect on reproductive function of feeding adult rhesus monkeys a diet of irradiated wheat flour and potato was evaluated. At the end of 3 months, the experimental and control animals behaved similarly with regard to their reproductive functions.¹⁹

1980 - The Joint Food and Agriculture Organization (FAO)/International Atomic Energy Agency (IAEA)/WHO Expert Committee on the Wholesomeness of Irradiated Food concluded that the 'irradiation of any food commodity up to an overall dose of 10 kGy presents no toxicological problems'⁸

1994 - The World Health Organisation reviewed a large number of animal feeding studies, mainly in dogs and rodents, looking at the safety and nutritional adequacy of irradiated food, and concluded that when requirements for good manufacturing practice are implemented, food irradiation is safe and effective.²

1999 - The Joint Food and Agriculture Organization (FAO)/International Atomic Energy Agency (IAEA)/WHO Study Group concluded that food irradiated with doses above 10 kGy (classified as 'High-Dose Irradiation') is both safe to consume and nutritionally adequate.⁷

2007 - Investigations on 8 out of 190 cats from a colony experiencing impaired coordination in their hindlegs were carried out. The findings provided circumsantial evidence that the exclusive feeding of a gamma-irradiated diet of reduced vitamin A content was associated with the development of the neuronal lesions, leading to a syndrome of feline leucoencephalomyelopathy (a neuro-degenerative disorder of the white matter of the brain and spinal cord).⁹

2008 - Following on from the 2007 study, the same researchers investigated the effects of 'typical'and 'high end' doses of gamma irradiation, and of pasteurisation on the amounts of fat, protein, carbohydrate, taurine, certain vitamins and peroxide in commercially available dry cat, dog and rodent diets. They found that the only treatment-related changes occurred with vitamin A and peroxide. Both doses reduced the vitamin A level in the cat diet to below recommended allowances for growth and reproduction, only the high dose reduced the vitamin A content in the rodent diet, and neither dose altered the vitamin A level in the dog diets. Irradiation increased the peroxide content of all 3 animal diets. ²⁰

2009 - A study reproduced leucoencephalomyelopathy in cats similar to spontaneous outbreaks by feeding a gamma-irradiated dry diet with elevated peroxide and reduced vitamin A concentrations.⁵

2009 - Between June 2008 and March 2009, 87 cats in Australia developed symmetrical hindlimb ataxia, paraparesis, tetraparesis, paraplegia or tetraplegia in association with eating an imported, irradiated dry pet food.⁴

2009 - A study investigating multiple sclerosis in cats found that cats fed an irradiated diet during pregnancy developed a severe neurological disease, resulting in severe myelin degeneration. On returning to a normal diet, those cats recovered slowly withing 3-4 months. No dietary deficiencies or toxic accumulations were found in the food or in the tissues from affected cats.¹¹

Studies have confirmed the general safety of irradiated food at doses typically used for product for human consumption (i.e. <10 kGy). However, due to the significant reduction in some vitamins, other nutritional factors and increase in lipid oxidation at doses over 25kGy, irradiation of foods that will be consumed as a significant part of an animal's diet (e.g. kibble) is not supported by DAFF.¹

Which pet foods are irradiated?

Numerous studies have shown that irradiated pet food is not safe for consumption by cats. The use of gamma irradiation for imported cat foods and treats is therefore no longer offered as an option for importers as of 2009¹³, and in line with this, we do not recommend feeding cats any irradiated food products.

For multi-pet households, care must be taken to prevent cats from consuming any irradiated dog food products.

In approving the import of pet foods, DAFF assesses the risk of those foods based on the country and species of origin of each ingredient, and the processing of those ingredients and the final product.

If the product and/or it's ingredients have been heat treated sufficiently (according to regulations), the import is approved. For those dog food products which do not meet the requirements, importers have the option to irradiate the foods.

If importers choose to irradiate their products, the Australian Standard for the Manufacturing and Marketing of Pet Food requires that the product will be labelled 'must not be fed to cats'.¹³

Is irradiated food safe for dogs?

Irradiation is a method of ensuring food safety and minimising the potential risk of pathogenic bacteria, viruses and food-borne parasites to your dog. There are currently no studies linking irradiated dog food products to any ill-health effects in dogs. Along with pathogenic bacteria, metals, pesticides, illegal dyes and more, irradiation is being investigated by the US Food and Drug Administration, as one of many potential causes of illnesses in pets relating to jerky treats. At this stage however, their testing has not implicated any specific agent/s as the cause.

In line with Australian standards and regulations, at Pet Circle we do not sell any irradiated food products for cats, or any irradiated complete and balanced dog foods.

We recommend limiting the amount of treats to no more than 10% of your pet's daily calorie intake (whether irradiated or not for dogs) to ensure that their overall diet remains complete and balanced. Keep treats as just that - a treat for good behaviour, a well-deserved reward. Shop from our range of Australian-made dog treats and cat treats for treats that align with Australian standards of food-safety and manufacture.

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Irradiated Pet Food

What is irradiated pet food?

Why is some pet food irradiated?

How does gamma irradiation work?

What is the evidence regarding irradiated food safety?

Which pet foods are irradiated?

Is irradiated food safe for dogs?

Further Reading

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Save up to 5% on selected brands* Learn More

Irradiated Pet Food

What is irradiated pet food?

Why is some pet food irradiated?

How does gamma irradiation work?

What is the evidence regarding irradiated food safety?

Which pet foods are irradiated?

Is irradiated food safe for dogs?

Further Reading

Save up to 5% on selected brands^*
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