by Andrew Prest, PhD Microbiology

For pet food manufacturers the main hazards are:


Many of the same pathogenic micro-organisms that affect humans also cause disease in companion animals. For example, improperly canned dog food has a similar risk (likelihood x severity of impact) of botulism due to toxin production by Clostridium botulinum as it has for human foods.

Likewise, while adult dogs are generally less likely to be symptomatic than humans, Salmonella enterica infections in dogs are relatively common, and salmonellosis can be a serious disease in puppies and elderly animals leading to severe diarrhoea and in some cases death.

Recent outbreaks have shown that Salmonella can survive on dry pet foods for extended periods of time (over a year) and serve as a vehicle of contamination and infection to both the pet and the pet owners. In addition, Salmonella has repeatedly been implicated in outbreaks where contamination rates were very low down to #1 cell/g.

A number of large recalls have been undertaken by manufacturers after dry pet foods and treats have been found to be contaminated with S. enterica or manufactured with ingredients that were subsequently found to be contaminated with the pathogen.

For example, a substantial portion of the products recalled as a result of the widespread contamination of peanuts and peanut flour with S. enterica were pet foods. Thus, it is critical that pet foods are produced in a manner that prevents Salmonella contamination.

Managing Salmonella contamination in the production of pet foods can be very challenging as many of the raw materials are naturally contaminated with Salmonella especially meat destined for rendering). Therefore, it is crucial to perform a risk assessment to understand which materials and processes pose the most risk and develop an effective control plan that addresses and minimises the potential product safety concerns.

This is why an effective HACCP program comes into play – Purpose – People – Process – Plant. Explaining the Why (or the purpose) of doing anything is so important and yet so many companies fail to do it well. Paraphrasing Nietzsche – ‘With a ‘Why’ we can ensure any ‘How’’.


There are 3 types of chemical contamination that can occur in pet foods. These are natural, misformulation and adulteration.

a. Natural chemical contamination

The most commonly isolated natural contaminants in pet foods are mycotoxins.

Aflatoxins are the most common mycotoxins associated with pet food recalls in the U.S. Other mycotoxin contaminants also have been reported. Aflatoxin production is associated with the growth of yeasts and molds on typically grain and other dried feed material.

This can occur on field crops or in storage. Temperature, humidity, drought stress, insect damage, and handling techniques all influence mycotoxin production.

Effective controls and maximum limits must be in place on vulnerable raw materials to manage this risk because mycotoxins are not destroyed by heat processing (e.g. extrusion or can retorting).

Early clinical signs of aflatoxicosis include feed refusal, anorexia, weakness and obtundation (reduced alertness), vomiting, and diarrhea. Later, petsbecome icteric (jaundiced), often with melena or frank blood in the faeces, hematemesis (vomiting blood), petechia (bleeding under the skin), and epistaxis (bleeding from the nose). In most cases the animals recover but some do not if the levels are acutely high.

b. Misformulation chemical contamination due to human error

Misformulation is another cause of adverse reactions to pet foods in cats and dogs. Hypervitaminosis D and thiamine deficiency have been reported recently. Other misformulations have involved excesses of methionine and vitamin A. Addiction Foods adopts checks and balances to ensure the correct ingredient are added to each production batch. This is a Critical Control Point (CCP).

c. Chemical contamination due to Adulteration (deliberate product abuse for economic gain or Food Fraud)

Early in 2007, Melamine was detected in cat and dog food after several reports of renal failure in cats and dogs consuming commercial pet foods in the U.S. Melamine which is not a food ingredient was being used illegally to artificially boost the protein content of food.

Estimates of the number of pets affected range from hundreds to thousands. Analysis of 451 cases matching the definition of melamine toxicosis found that 65.5% were cats and 34.4% were dogs. The case mortality rates were 73.3% and 61.5% for affected dogs and cats, respectively.



Physical hazards include Glass, metal, wood, plastic, stones, bones. Any one of these can cause choking or laceration if consumed. Metal detector and X-ray machines can be used to detect extraneous metal and dense material respectively.

For more detail please click on this FDA link.

Regardless of whether the focus is human or pet nutrition, the ability to manufacture and distribute safe products is a prerequisite for marketing a food product.

For example, the US Food and Drug Administration clearly articulated its expectations that pet food be manufactured under conditions similar to those that it requires for human food.

These changes in consumer expectations and accompanying regulatory interest are likely to have major impacts on the pet food industry, particularly for dry pet food products. The most obvious will be a wide scale need to upgrade facilities so that they meet the requirements for the production of human foods.

However, it will also have an impact on all operations as the need for more care in the acquisition of ingredients, the maintenance of records and the level of quality assurance will be expected by both retail markets and consumers.

READ ON: Key nutritional parameters and how they influence food safety

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About Dr Prest
Andrew Prest is the Founder and Managing Director of Sustainability Systems. He has extensive theoretical and practical understanding of food manufacturing processes and systems having held senior management positions with major global food and beverage manufacturers for over 20 years supported by a Masters in Food Technology and Quality Assurance and a PhD in Food Microbiology. Andrew has significant experience in auditing and integrated systems management within the Quality, Food Safety, Health & Safety and Environmental Management sphere.

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