Wondering about antibiotics in cattle feed?


Jean L Clavelle

Farm Animal Council of Saskatchewan


There has been much discussion on antibiotics that go into livestock production and their influence on antibiotic resistance.  Antibiotic resistance is so incredibly complex that not even the scientific community fully understands all of the causative factors.  We don’t have the space to tackle that topic here but I would like to chat about antimicrobial use in cattle production – in particular a group of medications called ionophores – as they are a widely used tool by cattle producers and wildly misunderstood by the general public.

Rumen diagram

The rumen is the main digestive center.

So let’s start from the beginning.  Cattle are considered “ruminants”, a class of animals which have not just one stomach but four (yes you read that right – 4 stomachs!).  Of the four compartments, the Rumen is the first and largest, and the main digestive centre.  The rumen is filled with billions of bacteria that are able to break down grass and other coarse fibrous materials (such as hay and straw) that animals with only one stomach (including humans, chickens and pigs) simply cannot digest.

Bacteria found in the rumen have a symbiotic relationship with ruminant animals.  Bacteria break down feed into various nutrients that are absorbed and used by the animal.  Without rumen bacteria, the animals themselves would not be able to access the nutrients found in highly fibrous feeds.

Interestingly enough there are different types of bacteria in the rumen.  Some are very efficient – they produce a greater proportion of nutrients that the animal can use for energy and only a small proportion of ‘waste’ energy that cannot be used by the animal.  Other types of bacteria however are inefficient in that they take nutrients from feed and turn them into mostly waste or non usable energy like methane gas, carbon dioxide, lactic acid, and heat that are essentially lost into the environment.

beef ration

Typical beef cattle feed

So how do antimicrobial drugs or ionophores play a role here?  First, they are mixed into the feed at tiny amounts (anywhere from 11 to 33 parts per million) where it’s consumed with their daily diet.  Ionophores work by reducing the number of less efficient bacteria which then allows for the more efficient bacteria to grow and function.  This means there is less gas released into the environment, the animal requires less food for the same amount of growth, and less energy is lost to other inefficient processes.  This is another tool that has allowed producers to be more efficient with less waste.  A management strategy that is safe for animals, humans and the environment.

Now, I’m sure you are wondering if they are safe.  Ionophores are considered to be of “low importance” to human medicine signifying that they are not and never have been used in human medicine.  That is because ionophores work specifically and only on bacteria in the rumen.  The Beef Cattle Research Council noted that drug sales for use in human medicine did not include any ionophores (none have ever been used in human medicine) while drugs of “low importance” (such as ionophores) accounted for 91% of drug use in cattle production.  So you may hear that medications are widely used in livestock production but the drugs most commonly used – ionophores – are  considered extremely safe and have little or no impact on human medicine.

You might also be interested to know that this antimicrobial drug use is highly controlled.  Health Canada’s Veterinary Drug Directorate approves the use of medications for animals once they have gone through an extensive investigatory process to confirm they are safe.  Then the Canadian Food Inspection Agency monitors the use of drugs at feed mills and on farms to ensure they are being used according to label instructions.  In addition, most feed mills in Canada are part of a HACCP based program called FeedAssure which helps to monitor the use of medications (see the link below for more info on this program).   Producers who are a part of the Canadian Verified Beef Program must also be able to show how what and where medications are being used to maintain their status in the program.

Yes, these medications are used in cattle production and yes they are antimicrobials but as you now know they have little or no impact on human health.  So hopefully this answers a few questions for you on antimicrobial use in Cattle Production.

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