The warning follows the deaths of several cattle near Wangaratta after they gained access to a burn site containing treated timber.
Treated timber, which is commonly used in fencing, yards, and landscaping, is often preserved with copper chrome arsenate or CCA, a chemical that protects wood from rot and pests.
CCA contains arsenic, which becomes significantly more toxic when the timber is burnt.
Agriculture Victoria veterinary officer Dr Lydia Nicholson said the animals showed severe neurological symptoms including staggering, blindness and collapse before dying.
Investigations revealed the burn pile included treated pine posts, commonly used in fencing and yards.
These timbers are often preserved with copper chrome arsenate, which contains arsenic.
“When treated timber is burnt, the toxin becomes concentrated in the ash and debris,” Dr Nicholson said.
“This material can be highly palatable to stock, and in this case, every animal with access to the site died.”
Landholders are also being warned about dumping garden clippings into paddocks or burn piles.
Many common plants, including oleander, foxglove, yew, rhododendrons and some sugar eucalypts, are toxic to livestock, with dried clippings often becoming more attractive to animals.
The Victorian Environmental Protection Agency said treated pine waste should be taken to local resource recovery centres, or to licensed landfill sites.
More information on how to dispose of treated pine and toxic waste can be found on the EPA Victoria website.
