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Antimicrobials: A Privilege Not A Right

01 April 2015

CANADA - The Beef Cattle Research Council (BCRC) has produced a video explaining to producers what they need to know about anti-microbial drugs, and how to manage resistance.

Anti-microbials are a class of drugs that kill bacteria.

They have two modes of action, the first being killing all the bacteria, with the host immune system cleaning up the damaged tissue. The second mode of action is suppressing the growth of the bacteria enough so that the host immune system can come and clean up the rest.

Anti-microbials are used in human medicine, but also in all sorts of agriculture, mostly in livestock. In the feedlot industry, they are also used to treat individual animals, or at high-risk times such as when the animals arrive at the feedlot.

However, resistance to anti-microbials is a global health threat. Resistance does also affect beef producers, limiting ability to protect animal welfare, so producers need to be kept informed on these issues.

Dr Reynold Bergen is Science Director with the Beef Cattle Research Council. He said that important distinctions are made between those that are useful for human medicine, and those that are not.

There are 4 categories – low (IV), medium (III), high (II) and very high (I) importance for human health. The low category provides almost all of the anti-microbials used in beef cattle rearing, and this category is not important in human medicine at all.

Most of the remaining anti-microbials used in beef production are from the medium category, and these are only used to treat relatively minor bacterial infections in humans. Examples include Liquamycin, Aureomycin and Terramycin. There are many alternatives for the medicines in this category.

Very high is the most critical category, and these are used for very serious bacterial infections. In beef cattle, less than 1 per cent of the drugs used fall into either the high or very high categories.
“What’s really important about that category is that if those don’t work, we’ve got nothing else,” he said.

In the beef industry in Canada, there are drugs from all four of those categories licensed and available for use. The BCRC said that it’s only appropriate to use drugs from each class in a situation where the benefit to the animal outweighs the risk of resistance developing.

The BCRC recommend producers to find out which drugs on their farms fall into the high and very high importance categories, and discuss with their veterinarian when and why to use them.

Vets give recommendations based on how well the drugs are working in the past and how well they work now across the industry, helping to decide what drugs to use and how and when to use them.

The most responsible action to take is the one that will give the best probability of curing the animal, with the lowest possible impact on human health. 

To manage resistance, there may be better ways of rearing cattle that will prevent the need for anti-microbials to be used in the first place.

One example is low-stress weaning, giving calves more chance to adapt to their environment. In addition, pre-weaning vaccination has been a big success.

This involves giving the vaccinations 2 weeks before the weaning process, giving the calves stress-free time to develop the immune response needed for the vaccine to work. That way, they already have the immune protection they need before they are transported elsewhere.

Anti-microbials can be managed more effectively, and sometimes not used at all if the cattle arrive with all their immune protection already in place.

TheCattleSite News Desk

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