Livestock production: Selective and sensible use of antibiotics to prevent microbe resistance

Calls to reduce the use of antibiotics are becoming more frequent. The aim is not to prevent the use of antibiotics, but to use antibiotics rationally and carefully, so that we can prolong the useful lives of current antibiotics, and comply with residue regulations.

Antibiotic resistance is a global concern. Misuse, which includes taking antibiotics unnecessarily for lesser ailments, or to compensate for poor hygiene, increases microbial resistance to antibiotics in human and animal populations.

The rational use of antibiotics does not forbid the use of antibiotics. Rational people understand that it’s wise to use antibiotics cautiously. There is much a farmer can do to reduce the build-up of anti-microbial resistance. The first is to understand that these drugs are not a cure-all for every problem in the herd or flock.

The outflow of new antibiotics has virtually run dry. Many bacteria are resistant to the older, and to the more recently developed, antibiotics. Some analysts predict that antibiotics will only be useful for up to a century or less.


Anti-microbial restistant (AMR) micro-organisms can develop in our food chains and move from animals to humans through direct exposure, consumption or via the environment.

The first priority on the farm is to keep the animals healthy by providing enough and proper feed and keep their surroundings clean and dry.

Your first priority is to keep your animals fed and healthy.
Your first priority is to keep your animals fed and healthy.


Always ask the vet before you use antibiotics to make certain that you have the right antibiotic for the disease and for the type of animal. Read the insert to double check the drug, the dose and the application method. that you use the right type of antibiotics for the disease and the type of animal.

Mark treated animals with chalk or tape, or another identification method if you have one. This way you and your staff can identify animals who are on antibiotics.


Use antibiotics at the right dose. It is highly irresponsible to under-dose with antibiotics. The animal is unlikely to recover and the microbes have a ‘free run’ at developing resistance to the drug.


Good biosecurity protects your farm from diseases and has a positive effect on reducing antibiotic use.

Quarantine animals to make sure they are disease-free when you move them from one farm to another. Remember that disease-free animals may be carrying bacteria with resistant genes. These genes could be transferred to on-farm disease causative bacteria. Quite suddenly, the effective antibiotic you’ve been using for years, will become ineffective.

Visitors, feed trucks and free-living animals like rodents are all possible carriers of bacteria which may threaten your animals.

Limiting visitors, cleaning feed and other trucks before they come onto the farm, and controlling rodents are biosecurity measures that a modern farmer implements on his or her well-run farm.


The withdrawal period is the time which must lapse between the last antibiotic treatment and the use of either milk, eggs or meat from the animal.

Each antibiotic has a different length of stay in the body of the animal, which may change according to the type of animal.

Withdrawal times also differ according to product type. Consult your vet and read the insert that comes with the drug.

Rather than taking a blanket antibiotic cover approach over an extended period, use antibiotics at critical times just before animals would be likely to pick up disease. If a few animals become ill during the antibiotic-free gap, they could be treated individually. For example – Blanket treating your cattle with an antibiotic to fight the threat of a disease like Anthrax would be an example of a critical time.


The fewer bacteria that vulnerable animals encounter, the smaller their chances of becoming ill. A single bacterium rarely causes disease. There usually have to be at least 100 bacteria, and more likely a thousand or more, before disease takes hold.

Hygiene is critical for disease control. Clean dung and pus, that carry millions of bacteria, away as quickly as possible.

Rodents carry many bacteria and uncontrolled rodent populations readily infect feed with urine and faeces.

All-in, all-out systems, in which animals are raised and then marketed, decrease the build-up of resistant bacteria. Once the animals have been sold, the farmer can clean out pig sties, poultry houses, weaner camps and feedlots. The sun is an excellent ‘antibiotic’ and can play an important role in keeping bacteria down.


Ensure that disinfectant washes are at the correct strength, the milking machine is treated according to manufacturer standards and cows with mastitis are milked last. Do not feed raw milk from cows with mastitis to calves or other livestock. Bacteria can multiply rapidly in milk standing at ambient temperature for an hour or two, and spreading bacteria from treated quarters around the farm, will also spread antibiotic resistant bacteria. The low levels of antibiotics in mastitic milk promote the development of resistant genes.


The bacteria that cause pneumonia are coughed or breathed out, and animals in close contact can inhale a lethal amount. Animals that are more spread out, and not overcrowded, will inhale only a few bacteria.

Don's keep too many animals in a closed space, and ensure their space is clean and dry.
Don’s keep too many animals in a closed space, and ensure their space is clean and dry.

Contaminated water may carry virulent bacteria

This may be seasonal, with a higher concentration of bacteria during times of drought. Chlorinating the water would decrease bacteria. Chlorination could be strategic, during dry seasons and crucial times for general farming. Dairy farmers would be wise to ensure that their water is always chlorinated.


Be pro-active and vaccinate your animals against preventable diseases in your region. This decrease the chances of your animals getting ill and needing antibiotics.

  • Most of the information for this article was provided by Dr. Marijke M Henton (, specialist veterinarian (bacteriologist) at Vetdiagnostix (

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