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Should Canadians be concerned about antibiotics in food animals?

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Last week in part one of this three-part series, we explained why and how antimicrobials (of which antibiotics are one type) are used in beef cattle. This week we’re exploring the causes for concern over that use.

We continue our conversation with Dr. Sherry Hannon, research team lead and veterinary epidemiologist at Feedlot Health Management Services Ltd.

How long do antimicrobials stay in an animal’s system?

There are many different antimicrobials labelled for veterinary use in cattle in Canada. Each is classified according to its uses, its effect on bacteria and the way it works.

“As part of the label, a ‘withdrawal period’ – a period of time before which the animals are not allowed to enter the food chain – is specified. Some antimicrobials have a zero day withdrawal period (they are eliminated from the body within a very short period of time), while others are known to stay in the body for much longer periods,” Sherry explained.

Causes for concern in the use of antimicrobials

Sherry explained that there are two main concerns related to the use of antimicrobials:

1. Antimicrobial residues

A residue is a remnant of the antimicrobial molecule itself or a degradation product of that molecule, left in the animal after harvest.

“For each antimicrobial, a level of residues (usually extremely low) has been deemed to be acceptable for human health through rigorous safety trials,” said Sherry.

“Therefore, meat that goes for sale to people must be at or below that level. The withdrawal period for each antimicrobial defines the amount of time that must have elapsed from the last dose before an animal can be harvested for meat, thus ensuring any possible residues are below the acceptable level and safe for human consumption.

As an added step of food safety oversight, meat at processing plants is regularly tested for residues on an ongoing basis as part of quality assurance and compliance monitoring.”

2. Antimicrobial resistance

According to Sherry, of greater concern than residues is the issue of antimicrobial resistance, which for many reasons, has become a global health issue. As the use of antimicrobials continues, for people and animals, there is increasing development of bacteria that are resistant to them.

“There is a potential for the presence of bacteria on meat or in the environment which carry resistance genes for particular antimicrobials, and this relates to the possibility that these bacteria could multiply or infect people,” she said.

The role of continued research and monitoring

“The above concerns are actively addressed through continued research, regulatory requirements, veterinary oversight, antimicrobial stewardship practices, and producers’ commitment to provide safe and nutritious beef,” noted Sherry. “In addition, appropriate cooking of beef further protects against these concerns by inactivating any residues present, or by killing any viable microorganisms,” she stressed.

The Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) monitors and describes antimicrobial resistance (and some use) in retail meat, on farm and in animal and human populations.

Stay tuned for part three of this series, in which we’ll discuss how food safety is ensured when antibiotics are used in cattle – and ongoing changes to regulation.

In the meantime, check out part one, ‘Antimicrobials and food production: 4 reasons antibiotics are given to beef cattle’.

Antimicrobials and food production – 4 reasons antibiotics are given to beef cattle

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Some Canadians have questions about antibiotic use in farmed animals. In an earlier post, we looked at the science behind the use of hormones in beef cattle. This week, in part one of a three-part series, we’re exploring another hot topic – antibiotics.

First up, an explanation of what antibiotics are, and how and why they are used.

Antibiotic or antimicrobial?

An antimicrobial is any agent that is used to treat microbial infection. An antibiotic is one type of antimicrobial, specifically made from natural microorganisms.

When looking at the safety or issues of using antibiotics in beef cattle, it makes the most sense to discuss the use of antimicrobials as a whole, rather than only antibiotics.

We spoke with Dr. Sherry Hannon, research team lead and veterinary epidemiologist at Feedlot Health Management Services Ltd. to learn more about the use of antimicrobials in feedlot animals.

Sherry explained that there are four main reasons for the use of antimicrobials in feedlots:

#1 To treat disease

“Diseases such as respiratory disease, arthritis and other lameness, abscesses, etc., are effectively treated with antimicrobials in injectable or oral form,” said Sherry.

#2 After surgery or injury

Antimicrobials are used to prevent infection in individual animals after specific events.

#3 As a preventative

Antimicrobials are sometimes used when animals have been exposed to disease, or unfavourable environmental conditions, and are at risk from an outbreak of infectious disease. They are also fed to groups of cattle at specific times to help prevent common diseases.

“Based on clinical field trials, we know that specific groups of animals may already be sick by the time they reach the feedlot after weaning, co-mingling in auction markets, and transport,” explained Sherry. “Antimicrobials help us prevent outbreaks that could spread through the herd.”

#4 To improve growth and production

The use of antimicrobials have historically been used to improve rumen function and enhance growth and production of meat, but this use is declining, and becoming increasingly regulated, due to the risk of antimicrobial resistance. We will discuss antimicrobial resistance further in part two of this series.

When antimicrobials are withheld

When an animal is sick, or at risk from disease, it would be cruel to withhold treatment.

“There are three main health implications when antimicrobials are withheld,” Sherry noted:

    • Poor animal welfare – animals would become sick or die.
    • Greater potential for spreading of disease among animals in a pen.
    • Food safety concerns increase because animals are more likely to have infections when sent to slaughter.

Stay tuned for next week when we will discuss the causes for concern around the use of antimicrobials in beef cattle, and what’s being done to address them.

In the meantime, check out ‘Beef and hormones: what the science says’.