Your Reading List

Stop Recycling Pathogens In Animal Feed

“Something needs to be done to show reduced levels of these frequencies.”


Two recent high-profile cases of foodborne illness have once again raised concerns about the safety of North America’s food supply.

Last year, 20 Canadians died and 36 more sickened after eating processed meat contaminated by Listeria monocytogenes from a Maple Leaf Foods plant in Toronto.

More lately, the Peanut Corporation of America filed for bankruptcy following 575 illnesses, including eight deaths, in 43 U. S. states from salmonella poisoning traced to contaminated peanut products at a company plant at Plainview, Tex.

The listeria outbreak was the result of inadequate plant sanitation. So was the salmonella outbreak.

But the incidents raise the larger issue about the increasing frequency of foodborne illnesses and why they occur.

For Richard Holley, one of Canada’s leading food scientists, the issue is not just what comes out of processing plants. It’s what enters animals’ mouths before they go to the plants.

In other words, it’s about contaminated livestock feed.

It’s scientifically accepted that bacteria and other zoonotic pathogens from colonized food animals can be transmitted to humans through the food supply. (Zoonotic means transmissible from animals to humans.)

But Holley takes it one step further by saying animals get these pathogens through the recycling of animal waste into livestock feed.

The result is a cycle of recontamination, which good agricultural practices and on-farm HACCP programs fail to solve because they do not consider the use of pathogen-free feed important, said Holley, a University of Manitoba food science professor.

“It’s a no-brainer for me, based on evidence that currently exists in the literature, there is a link between feeding animals zoonotic pathogens and the animals shedding them,” he said in a recent interview.

“When you take a look at the increasing frequencies with which animals are contaminated by these organisms that find their way into produce, something needs to be done to show reduced levels of these frequencies.”


The only way to accomplish that is to strictly control and monitor the way livestock feeds are manufactured and distributed, said Holley.

Currently, there’s no restriction on what goes into livestock feed as long as it doesn’t make animals sick, he said.

As a result, animal feed ingredients can include rendered animal products, plant-and animal-based fats, antibiotics, metals and even poultry litter (the latter more so in the U. S. than in Canada).

Recycling animal waste into livestock feed has been practised for years, partly as a way to cut feed costs.

But because of these feeding practices, “etiologic agents” (things that cause disease in humans) abound in animals and even in the food they produce, said Holley.

These include bacteria, bacterial toxins, viruses, fungi, protozoans and parasites.

As a result of recycling pathogens in feed, infectious agents are now endemic in food animals. Nearly 100 per cent of chickens have campylobacter, 50 per cent of hogs are contaminated with salmonella and four per cent of cattle carry the potentially deadly E. coli 0157:H7 bacteria strain, Holley said.

In a recent article in Prophylaxis, the Ontario Food Protection Association newsletter, he noted the risks of recycling zoonotic pathogens in the food supply.

Holley said he’s not opposed to including animal protein and other byproducts in livestock feed because they can have nutritive and medicinal value.

But he called for stricter regulation of the livestock feed industry, including programs to prevent cross-contamination with zoonotic pathogens.

“They would be instituted in such a way that there would always be a critical control point allowing for the elimination of these zoonotic pathogens in animal feed. In addition, (they) would ensure that the final products were not cross-contaminated at any time.”

Holley said industry must take responsibility for this because the only people who can make sure it happens are the ones actually doing the work.

At the same time, food safety in Canada goes beyond having more inspectors and end-product testing, he said.

“It relates to developing a better co-ordinated food inspection system in this country and development of better foodborne surveillance programs.” [email protected]

About the author



Stories from our other publications