Lead toxicity is unfortunately a common diagnosis in North Western NSW, despite it being preventable in most cases. The most common source of lead in this area is batteries, either left in the paddock or contained within old car and truck carcasses. Generally the landowners are unaware of the presence of the batteries until the diagnosis is made.
District veterinarians were called to investigate a single 8 month old Charolais x steer that was observed standing along a fence, separate to the mob. It was dull, depressed and able to be approached and touched - which was abnormal for this animal.
The steer was part of a mob of 50 that had been moved 2 weeks ago to the property near Narrabri from another property on the mid north coast of NSW. The cattle had recently been vaccinated with a 7-in-1 clostridial vaccine. They were feeding on sparse native pasture, an oat crop and had access to hay (Rhodes grass hay brought from the coast). Water was from a bore in a trough, and also a dam which held rainwater.
On arrival at the property the steer was recumbent, but was able to rise when approached. It was ataxic and circling (Video 1).
The steer was blind and seemingly unaware of our presence. During examination it progressed rapidly to recumbency, paddling and inability to rise (Video 2).
It was euthanased for post-mortem, with initial differential diagnoses including sporadic bovine encephalomyelitis, polioencephalomalacia, and lead toxicity.
The post-mortem revealed no gross abnormalities. A small amount of gravel-like material was found in the reticulum, but no evidence of metal.
The next day a second steer was found recumbent but died prior to veterinary examination. A post-mortem revealed a small amount of metallic material in the reticulum (Figure 1). Widespread enteritis with petechiation of the intestines was also noted.
At this stage the owner reported he had found a battery in an old truck that the cattle had had access to, which showed evidence of being chewed on by the cattle.
Blood results from the first steer returned a lead level of 7.6umol/L (Normal <0.2umol/L) which is high. Subsequent testing of remaining samples was not undertaken.
The remainder of the mob was tested with a further 5 steers returning high lead levels. These animals were detained on the property.
The two steers that died at this property presented with classical clinical signs consistent with lead poisoning. The presentation was of the subacute form which is typical of cattle of this age. Circling, anorexia and blindness in one steer and the other reported to be dull, blind and anorexic prior to death.
Post-mortem findings can vary from no gross lesions to some degree of abomasitis and enteritis with degeneration of the liver and kidneys and epicardial haemorrhages (Radostits, 2007). In the second post-mortem there was enteritis with petechial haemorrhages along the outer mucosal surface of the small intestines (Figure 2).
Only small particulate matter was found in the reticulum of the first post-mortem but some larger metallic particles were discovered in the reticulum of the second post-mortem (Figure 1), further confirming the diagnosis prior to laboratory confirmation.
An acute form of the disease which presents with a more rapid onset of clinical signs and in some cases sudden death is more common in calves less than 5 months of age owing to the better absorption of lead when on a milk diet as opposed to post weaning (Parkinson et al., 2010). It is also suggested that poisoning in this age group is the more common occurrence however in the authors' experience, lead poisoning is most common in young weaned cattle.
The inconvenience caused to landholders by a lead diagnosis can be substantial. Not only do all other cattle on the property have to be mustered and blood tested - at the owners expense - but the ongoing feed requirements for cattle who are detained for a 12 month period can be substantial, particularly during a drought.
In this case, the landholder was unaware of the presence of the battery, and also unaware of how inquisitive and destructive young stock can be in accessing seemingly inaccessible batteries within car and truck carcasses. According to advice by the manager of the stock, the cattle had access to the source of lead for a 24hr period only.
Rotary often organises battery collections as a fundraiser for their community works. Landholders should be encouraged to take advantage of these opportunities to clean up around their farms and reduce the risk of lead intoxication in their stock.