Lead exposure and poisoning in livestock
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Preventing lead residues in livestock products protects human health and Victoria's ongoing access to international markets.
Lead is highly toxic to livestock and humans and may cause sudden death in livestock.
All animals that have been exposed to lead sources must be managed to ensure that animal products for human consumption or export do not contain lead residues.
How are livestock exposed to lead?
Livestock find lead palatable and will readily lick and chew on lead material. Younger animals may be more commonly affected as they are more inquisitive. Old batteries are the most common source of livestock lead poisoning. Battery cases become brittle and are easily broken open by stock.
You can prevent lead poisoning by removing and/or securely fencing off lead sources from livestock. All rubbish dumps should be fenced, and livestock should not graze areas where old rubbish dumps or burnt machinery is located.
Other sources include: sump oil, posts painted with sump oil; linoleum; grease; lead paint and old paint tins; lead panels, weights and shots; oil filters; lead-light windows; and old putty cans. Fragments may lodge in the stomach of ruminants and provide a reservoir from which lead continues to be absorbed.
What should I do if I think my stock may have had access to lead?
Lead exposure may cause death in livestock. In live animals, teeth grinding and blindness are the most common signs, however stock may also show muscle spasms, a lack of coordination, rolling eyes, head pressing and tongue paralysis.
Affected animals generally stop grazing and become dull and unresponsive.
If an animal shows clinical signs, it has generally ingested a large amount of lead. Euthanasia may be the most humane option for the animal, especially due to the likelihood of unacceptable residues that may linger for years.
Treatment of livestock showing clinical signs must be administered by a veterinarian and is often ineffective. Testing blood samples from exposed stock will confirm lead poisoning (defined as levels greater than 0.24 µmol/L).
It is important that a post-mortem examination is done, and blood and tissue samples are submitted for testing to confirm lead poisoning and rule out other diseases such as plant poisonings, polioencephalomalacia, grass tetany, or exotic diseases that cause nervous system symptoms.
What happens to my stock if lead poisoning is confirmed?
Agriculture Victoria’s policy for the management of lead residues in grazing livestock is based on a national agreement.
The policy aims to manage the risks associated with high levels of lead in meat, liver, kidney and milk that could adversely affect human health and impact Australia’s international trade in meat and dairy products.
Not all stock that have ingested lead will show symptoms, however their blood and tissue lead levels may be higher than the permitted maximum limit (ML).
All livestock that have had access to the lead source are regarded as contaminated until individual blood tests are completed.
Lead poisoning is a notifiable disease under section 7 of the Livestock Disease Control Act 1994 (LDCA), therefore any suspected cases must be reported to the Victorian Chief Veterinary Officer within 7 days.
How does testing of stock occur?
Any suspicion of lead exposure and related concerns should be discussed with your private veterinarian, who will sample exposed stock and liaise with Agriculture Victoria. Producers must also notify Agriculture Victoria of the suspicion and confirmation of lead poisoning on their property.
The cost of all laboratory analysis to confirm or exclude lead exposure, or enable change of lead status, is borne by the producer and will be undertaken by your private veterinarian.
Why is lead exposure so serious?
Lead is an extremely serious human health hazard, which is why lead residues in livestock must be managed so strictly. The World Health Organisation states that there is no known safe blood lead concentration in children:
- Lead exposure can have serious consequences for the health of children, including unborn babies. They are also at risk because they absorb more lead than adults.
- Even at low levels of exposure, lead can irreversibly affect brain development resulting in reduced intelligence quotient (IQ), increased antisocial behaviour and reduced educational success.
For further information about the health effects of lead in people, please see betterhealth.vic.gov.au: Lead exposure and your health.
Please contact your local Agriculture Victoria Animal Health Officer or District Veterinary Officer.