What are harmful residues in livestock?
A residue is what remains of a chemical or heavy metal (e.g. lead, arsenic, cadmium) inside an animal at a point in time. The residue may be the original substance or a derivative (metabolite) of the original substance. All chemicals and heavy metals cause residues but the time taken for a residue to break down varies depending on the substance and the animal.
Residues may be harmful when the amount of residue in the animal exceeds the maximum residue limit (MRL) for the chemical or heavy metal. The MRL is the maximum amount of residue allowed in a food to be safe for human consumption. MRLs are legal limits and penalties may apply if produce is sold which exceeds these limits.
Not all residues are harmful - products containing residues less than the MRL are considered safe for human consumption.
How do harmful residues occur?
Harmful residues may occur when:
- veterinary chemical label instructions or veterinary directions are not followed
- the withholding period (WHP) or export slaughter interval (ESI) of a veterinary chemical is not observed
- livestock are exposed to plant chemicals used to control weeds or insects
- unregistered chemicals are used on livestock – these chemicals don’t have WHPs and are of an unknown residue risk
- livestock access hazardous materials such as lead batteries often found in places like the farm dump, sheds, old yards, old house sites or painted materials
- livestock are grazed on land contaminated with persistent chemicals such as organochlorines (e.g. old potato paddocks, orchards, stock feed treated with a pesticide is given to livestock, like pickled grain).
How do you know if an animal has harmful residues?
It is difficult to tell if an animal contains harmful residues because not all chemical or heavy metal residues will cause signs of illness in animals.
It is important to note that the MRL establishes safe limits for humans not animals. Exceeding the MRL will not necessarily affect the health or welfare of an animal.
What happens if livestock contain harmful residues?
If you suspect your livestock may contain harmful residues, contact your local Department of Agriculture and Food, Western Australia (DAFWA) field veterinary officer for advice. Department staff are able to assist in the management of these animals before they enter the food chain.
WA has laws to manage harmful residues in livestock. These laws safeguard the public and market access by helping to ensure animals are not slaughtered if they contain residues in excess of the MRL.
DAFWA manages chemical residue laws under the Biosecurity and Agriculture Management Act 2007 and Biosecurity and Agriculture Management (Agriculture Standards) Regulations 2013.
Under these laws it is an offence to sell livestock containing residues in excess of the MRL. The department will investigate residue detections above the MRL and issue corrective actions. Penalties or prosecution may also result if harmful residues are found in food.
What can I do to avoid harmful residues in my livestock?
Keep livestock free of harmful residues by:
- following all veterinary chemical label directions or veterinary directions
- observing the WHP or ESI
- conducting a farm risk assessment to identify contaminated sites like old dips, spray races, farm dumps and areas sprayed with organochlorine chemicals (e.g. orchards, telegraph poles)
- testing soil in areas where organochlorines or other persistent chemicals are known to have been used
- restricting stock access to contaminated sites like farm dumps. Permanently fence, remove or bury potentially hazardous material in consultation with your local government authority or the Department of Environment Regulation
- avoiding lead exposure – prevent stock access to lead batteries, lead-painted machinery or buildings, sump oil treated fence posts,old house sites etc
- avoiding exposure to plant chemicals used to treat weeds or pests. Follow grazing withholding periods (GHP) or other label withholding periods
- identify animals exposed to residues – ensure livestock with residues do not end up in the food chain
- check chemical records before selling animals – correctly declare if sale animals are inside or outside of the WHP on the National Vendor Declaration waybill.
- be aware of the chemicals you use on your property and livestock
- keep livestock safe from unnecessary chemical exposure or use
- prevent access to residue risk areas (e.g. farm dumps, chemical storage areas, sheds) and remove any chemical risks left in paddocks such as old machinery parts, chemical drums or batteries
- help maintain WA's well-earned reputation for safe, reliable meat, milk and fibre products. These markets were worth $1.6 billion in 2014/15.