Every year small numbers of livestock die or are quarantined following exposure to lead. Usually these animals have eaten lead batteries found in the farm dump or left in the paddock.
Other lead poisoning cases occur when hungry stock seek alternative feed sources. Younger stock are more susceptible given their natural curiosity and relative size. Cattle are more likely to succumb to acute lead poisoning but sheep and pigs can also be affected.
Common on-farm lead sources:
- lead batteries, especially burnt ones
- painted surfaces – machinery, car bodies, sheds, yards
- paint tins
- sump oil
- grease and oil filters
- linoleum
- caulking, putty.
Lead batteries are the most common cause of lead poisoning and residues in livestock. Battery casings become brittle over time allowing animals to access the lead and lead salts. Burning batteries also makes the lead readily accessible to livestock.
Risk factors:
- cattle are inquisitive and appear to like the taste of lead. Lead has a sweet taste and some livestock are attracted to this
- younger animals are more likely to eat lead compared with older animals
- hungry stock may seek out feed around hazardous areas such as the farm dump or around sheds – take care during feed shortages
- reduced pasture cover may expose lead hazards not previously noticed
- agisting animals on unknown land – lead battery dumps may be present in grazing areas.
How to prevent lead poisoning:
To prevent lead poisoning and the possibility of lead residues in livestock, producers should:
- carry out a risk assessment: identify any areas on farm that could contain lead (such as farm rubbish dumps, old car/machinery bodies, painted surfaces, sump oil-treated posts, battery piles, vehicle sheds)
- where possible, remove the risk (that is, dispose of batteries at approved landfill sites) or
- securely fence off the risk (that is, fence the farm dump, sheds).
Signs of lead poisoning:
- dullness, unresponsive to sound or touch
- blindness, staggering, tremors
- death.
Seek immediate veterinary advice for livestock showing these signs. Lead poisoning can cause signs similar to other diseases that affect the nervous system such as plant poisoning, botulism, polioencephalomalcia (PEM) and metabolic diseases like grass tetany (magnesium deficiency).
Early detection is vital to help prevent continuing losses and to determine the appropriate treatment for sick animals.
Note: not all animals that have eaten lead show signs of poisoning but these animals may contain lead residues in excess of the maximum residue limit (MRL). Any livestock that have been exposed to lead must be tested for residues.
Diagnosis of lead poisoning
The diagnosis of lead poisoning is based on a history of access to lead and clinical signs. Lead poisoning can be confirmed by testing blood or tissues (liver and kidney) taken at post-mortem.
Lead tends to lodge in the fore-stomach (reticulum) of ruminant animals such as cattle, sheep and goats. This provides a reservoir from which lead can continue to be absorbed into the body and cause persistently high lead residues for months or even years.
National Residue Survey (NRS) testing at abattoirs will detect animals with elevated lead levels. When notified of such residues, Department of Primary Industries and Regional Development, Western Australia (DPIRD) officers will visit the property the animals originated from to determine the lead source and ensure other affected/exposed livestock do not go for slaughter. These animals are quarantined for a minimum of 12 months and must not be sold for slaughter during this period.
Treatment for lead poisoning
Treatment is mostly unsuccessful and only worth attempting during early stages of poisoning. It is vital to identify the source of the lead and remove the animals from the source immediately. Contact your local veterinarian for advice on treatment and follow all veterinary directions.
Treatments may include:
- vitamin B1 injections – to work on damage done to the central nervous system
- magnesium sulphate (Epsom salt) drenches – absorb lead from particles in the gut
- chelating agents – to increase the rate at which lead is eliminated from the body.
What to do if animals are exposed to lead
- contact your local department field veterinary officer regarding your suspicions - see the Livestock Biosecurity contacts webpage for your nearest officer
- seek immediate private veterinary advice if livestock show signs of poisoning
- arrange to have animals blood tested if you suspect animals have accessed lead.
If lead exposure is confirmed, DPIRD will advise you on how to ensure animals with residues do not enter the food chain.