Cropping & Soil
12 September, 2025
Chemical residue exposure risk to stock
WITH the dry conditions and paddocks looking a bit bare, it’s only natural to start eyeing those unused corners of your property.
Perhaps it’s the area around the old shed, the house paddock that hasn’t seen stock in years, or even that overgrown tree plantation.
Some might even be thinking about letting cattle into places like an old dip site or the farm rubbish tip.
Agriculture Victoria veterinary officer Dr Lydia Nicholson said before farmers swing open the gate, it’s worth taking a moment to consider what might be lurking in these spots, and whether they’re really safe for grazing.
“By opening up some of these areas, farmers may unknowingly expose their cattle to chemical residues,” Dr Nicholson said.
“Stock can readily pick up residues if they have access to localised areas of high-level contamination.
“A recent case near Wodonga served as a sobering reminder of how easily well-intentioned actions can pose serious risks to livestock.
“During a disease investigation, several cattle were found dead after displaying severe neurological signs such as staggering, blindness, and collapse.
“Post-mortem examinations and laboratory testing were conducted, but the key breakthrough came during a discussion with the landholder. It was revealed that a bonfire had recently been lit on the property, and the burn pile included treated timber.”
Treated timber, commonly used in fencing, yards, and landscaping, is often preserved with copper chrome arsenate (CCA), a chemical that protects wood from rot and pests.
Dr Nicholson said CCA contains arsenic, which becomes significantly more toxic when the timber is burnt.
“Burning concentrates the toxin and leaves behind ash and debris that can be highly palatable to livestock. In this case, every animal that had access to the burn site died.
“This tragic outcome highlights the importance of being vigilant about what goes into your burn piles. Even small pockets of contamination can lead to fatal consequences when stock gain access.
“Another thing to keep in mind is the legacy of older agricultural chemicals, particularly organochlorine (OC) pesticides such as DDT, dieldrin, and heptachlor.
“These chemicals were once widely used around sheds, yards, dip sites, and orchards, and can persist in the soil for decades.”
Dr Nicholson said that while you might not be using them today, residues can still pose a serious risk.
Meat processors routinely test for chemical residues, and if any carcase exceeds the Australian maximum residue limit (MRL), it is condemned for human consumption.
As the vendor, farmers may also be held legally liable.
“Farmers need to do their research about areas that may have been used for chemical storage or treated in the past,” Dr Nicholson said.
Common OC risk areas include buildings, yards, fences, stumps, and power poles treated for termite control; sheep dip sites used before 1963; old chemical containers or waste in farm rubbish dumps, and chemical storage, mixing, and disposal areas.
Others include lawn clippings from OC-contaminated areas, land used for potatoes or tobacco before 1986, land used for orchards before 1988, or vegetable production before 1986.
Dr Nicholson said if farmers are unsure, Agriculture Victoria holds historical records of known contaminated sites.
“Plus, speaking with previous property owners also help identify historical uses of some areas. In some cases, soil sampling may be needed but often, simply fencing off suspect areas is the safest and easiest option.”
Dr Nicholson added that this was just one more reason to walk the paddocks, ask the right questions, and take a cautious approach before opening up new ground to stock.
“A bit of local knowledge and forward planning can go a long way in protecting animal health, food safety, and your bottom line.”
For further information contact your local veterinarian or Agriculture Victoria veterinary or animal health officer.