Objective: To assess the validity of claims that heavy metal contamination from an open-cut mine caused the death of 226 cattle on a nearby farm over a period of 18 months, and to investigate other possible contributing factors.
Procedure: A retrospective assessment of previous investigations combined with additional chemical analyses.
Results: Extensive chemical analyses produced no evidence of heavy metal contamination associated with the mine. Analysis of bones indicated exposure to fluoride in greater than normal amounts. The main source of fluoride seems to have been gypsum that was included in a feed supplement and also ingested from fertiliser dumps on paddocks. The gypsum itself may have contributed significantly to the ill health. Other factors probably affected some classes of animals, notably the young calves.
Conclusions: What originally seemed to be a disease problem of single aetiology probably was an expression of interacting multifactorial causes. This investigation has highlighted the potential toxicity of gypsum to livestock and the need for further studies to establish its basis.