Antibiotic use

We believe that disease control in salmon requires a holistic approach. Good site management, fish husbandry and rigorous biosecurity measures are central to reducing the risk of disease outbreaks and controlling the spread of infectious diseases.

Vaccines are important in preventing disease outbreaks but cannot control all losses. Medication such as antibiotics are also important but should only be used as a last line of defence to avoid significant animal welfare issues and stock losses.  This mind-set means that we are continually working to develop proactive diet regimes and vaccines to allow our salmon to combat known illnesses and lead healthy lives.

Key facts:

  • Huon has not used antibiotics at sea (both in Macquarie Harbour and in South East Tasmania) since 2016 when a single pen was treated. Furthermore, Huon did not use antibiotics at any of our land based sites (ie hatcheries) in the 2019-20 financial year. 
  • The correct use of antibiotic is critical in reducing antimicrobial resistance which is why our Vets/fish health teams follow the World Health Organisation (WHO) guidelines for the use of antibiotics in livestock industries.
  • WHO does not preclude the use of antibiotics in livestock industries, including salmon farming.
  • Our Vets only prescribe antibiotics as a last resort and always following a full investigation, confirmation of diagnosis through laboratory testing of fish health samples and after confirming antibiotic sensitivity of causative organisms.
  • Huon voluntarily publicly reports all antibiotic use (marine and freshwater) as well as reporting their use to the State Government in real time.
  • Huon has not used antibiotics on our fish growing at sea since 2016 (one pen treated, equating to antibiotic use of 0.16 grams per tonne of salmon. Our use of antibiotics across our freshwater operations (ie hatcheries) is restricted to our non-consumptive flow-through hatcheries (which only hold on average around 20 per cent of our total smolt biomass). The last use in a hatchery was in January 2019—see below for details.
  • Antibiotics are administered by a qualified veterinarian and there is a strict withholding period which means that any traces are completely passed through the fish long before it is harvested.
  • Huon also participates in an annual national residue survey to monitor levels of therapeutants, ensuring we comply with a maximum residue limit.
  • Huon is also participating in research projects to assess antimicrobial resistance in collaboration with the Australian Government as part of its National Antimicrobial Resistance Strategy 2015-2019.

A last resort

We believe that antibiotics should only be used as a last resort which is why we practice a holistic approach to farming. Integral to our approach is good site management, low stocking densities, the development and use of vaccines, feeding a high-quality diet, and keeping our fish as calm and low stress as possible.

It has been four years since we have used antibiotics at sea, which was to treat a single pen of fish.

In January 2019, we used antibiotics to treat the small fish we grow in two of our freshwater hatcheries. The fish in these hatcheries were prescribed the treatment as they had Yersinia (a coccobacilli bacterium which is naturally present in some water).

We will never use antibiotics at our other hatcheries as these are closed-loop systems which rely on good bacteria within the waste treatment system to treat the water and as anyone who has taken antibiotics will know, their use kills both the good and the bad bacteria.


Types used

Huon does not use any of the antibiotics listed as Critically Important by the WHO – despite WHO guidelines stating that this would be acceptable under certain defined circumstances.

(WHO categorises all antimicrobials used in human medicine as either Critically Important, Highly Important or Important in the medically treatment of bacterial infections in humans; in effect placing a value/importance on each antimicrobial in terms of its effectiveness in combating bacterial infections).

Huon only uses Trimethoprim (Dihydrofolate Inhibitor) and Oxytetracycline (Tetracycline) which are on the WHO Highly Important list. All use is in early life stages, well over 12 months prior to harvest, significantly exceeding required withdrawal periods so there are no residue issues in final products.

The Tasmanian industry as a whole independently made the decision many years ago not to use antibiotics such as Oxolinic Acid (Quinolone) and Amoxycillin (Penicillin) which are compounds listed by the WHO within Critically Important classes of antimicrobials. This decision was made despite these particular antibiotics being used in salmon farming across other countries.


Preventing antibiotic resistance 

To prevent and control the spread of antibiotic resistance, the agriculture sector (including aquaculture) can:

  • Only give antibiotics to animals under veterinary supervision.
  • Not use antibiotics for growth promotion or to prevent diseases in healthy animals.
  • Vaccinate animals to reduce the need for antibiotics and use alternatives to antibiotics when available.
  • Promote and apply good practices at all steps of production and processing of foods from animal and plant sources.
  • Improve biosecurity on farms and prevent infections through improved hygiene and animal welfare.

 

Voluntary public reporting

We recently undertook to publicly and voluntarily report our antibiotic use. The volumes used in freshwater and marine operations can be found below:

Antibiotic used
Over Calendar Yr Hatcheries Marine Pens treated
2013 1.17 kg 21
2014 0.96 kg 23
2015 1.99 kg 0
2016 3.7 kg 1
2017 5.6 kg 0
2018 3.0 kg 0
2019 6.7 kg 0

 

Withholding period and residue testing

In the event that antibiotics are used in a population of fish at sea, we adhere to strict withholding periods which allows any therapeutants to pass through the fish before it is harvested for consumption.

In addition, Huon participates in an annual national residue survey to monitor levels of therapeutants, ensuring we comply with a maximum residue limit, which refers to the highest concentrations of a chemical residue that is legally permitted or accepted in a food, based on good agricultural and chemical use practices. Results of flesh testing can be found via the following website: https://www.agriculture.gov.au/ag-farm-food/food/nrs.

On occasion we also conduct voluntarily flesh testing which is not required by government regulations. When we do this, we publish the results on our website