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Antibiotic resistance in livestock - is it a concern?

November 13, 20234 min read

If you ever read the wonderful James Herriot series of books you know how much harder it was for farmers to deal with sick livestock in the days before antibiotics were available. Diseases that today are easily cured, such as mastitis, would often be a death sentence. 

Human and veterinary medicine dramatically changed when Sir Alexander Fleming discovered penicillin in the 1920s, revolutionizing the fight against bacterial diseases. This breakthrough not only changed human healthcare but also significantly improved the health management of our livestock.

For many years, antibiotics were a roaring success. New antibiotics were developed in the ongoing fight against disease but over the years, some of the bacteria got smart and started to develop resistance.

How resistance happens

Bacteria become resistant to antibiotics through a natural process of evolution. When we treat an animal with an antibiotic, the most susceptible bacteria will die off, but some may survive due to a mutation that protects them against the antibiotic's effects. These resistant bacteria multiply. The repeated use of antibiotics, essentially 'train' the surviving bacteria to withstand future treatments, which leads to bacterial strains that are much harder to kill with existing antibiotics. 

Superbugs, such as MRSA, have developed in humans. These can be highly resistant to antibiotics. The infections mainly occur in hospitals in patients who have been exposed to repeated long-term use of antibiotics.

While there is an increase in antibiotic resistance in humans worldwide, generally speaking, in New Zealand, the problem is small but growing.

Understanding Antimicrobials and Antibiotics

Rather than the term ‘antibiotic resistance’ you may hear about ‘antimicrobial resistance’ or AMR. Antimicrobials is an umbrella term for treatments that combat various germs such as viruses, fungi and bacteria. So antibiotics are an antimicrobial which specifically combats bacteria. 

AMR happens when the germs no longer respond to treatment. Antibiotics and other antimicrobials are vital tools for farmers and vets, and we need to use them wisely to avoid the emergence of resistance.

How would antibiotic resistance affect our livestock?     

As farmers, there are times when we need antibiotics for our animals. It may be an animal that has had an assisted birthing, an animal that has injured itself or an animal that has a bacterial infection either through a wound or disease. The antibiotic treatments can come in the form of injection, spray, ointments or as feed additives.

If antibiotics were no longer working, we’d need to develop new ways to fight common infections and probably lose a lot of animals in the interim.

Our pasture-based farming in New Zealand, and strict legislation, mean we don’t routinely use antibiotics unless prescribed by a vet for a specific disease. Because our animals aren’t subjected to a large amount of antibiotics, we don’t have a big problem with AMR.

sheep in the foreground with a vet holding a syringe in the background

Intensive farming and antibiotics.

Intensive farming presents a greater risk. In high-density farming operations eg broiler poultry, intensive pig farming or feedlots the close quarters and higher stress levels among animals mean that disease can spread rapidly. Farmers in these situations are more inclined to use antibiotics preemptively, raising the likelihood of resistant bacteria. 

Antibiotic resistance between animals and humans - is this likely?

Humans and animals share some of the same bugs.Bacteria do not respect species boundaries; they can move between animals and humans, posing a risk of transferring resistant bacteria. Although the risk is currently considered low, especially in our local context, it underscores the need for caution with how we use antibiotics on farms.

What can we do?

If we want antibiotics to remain effective, then we need to use them wisely. The best way to do this is to avoid as much as possible the need for antibiotics. Keep your animals healthy by providing a healthy environment and appropriate nutrition. 

In addition:

  • Only give antibiotics to animals under veterinary supervision.

  • Give the appropriate dosage for the weight of the animal.

  • If prescribed a course of antibiotics by the vet, give the entire course.

  • Vaccinate to reduce the need for antibiotics.

  • General farm hygiene is important - water troughs and sheds should be cleaned regularly.

  • Don’t bring resistance onto your farm - check the health status of new animals and quarantine them when they arrive on your farm.


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Amanda Bowes

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