A central nervous system disease occurred in a group of beef steers placed into confinement feeding pens during a period of prolonged drought and high environmental temperatures in Oklahoma, USA (September 2000). The steers began exhibiting neurological signs during the 3rd week after placement into the pens. Microscopic examination of brain tissue revealed lesions consistent with polioencephalomalacia. Tissue analysis for lead and evidence of water deprivation-sodium ion toxicity were negative. The steers had been drinking well water containing 3000 ppm sulfate. In addition, the total mixed ration contained 2950 ppm total sulfur. Total sulfur intake was calculated to be 77 g of sulfur per steer per day, which equated to 1% (10?000 ppm) of the ration on a dry matter basis. Based upon clinical signs, histopathology and high levels of sulfate and sulfur in the water and feed, respectively, a diagnosis of sulfur-induced polioencephalomalacia was made. No further cases occurred after the steers were provided water with low sulfate content.
A herd of beef cattle routinely fed cotton industry by-products was poisoned by disulfoton-treated cotton seed that was disposed in cotton gin trash. Disulfoton is an organophosphorus insecticide. Eighteen of 48 animals died. Blood acetylcholinesterase (AChE) levels were used to determine clearance of disulfoton from the surviving animals, and to determine when the animals could be sold. At 36 days post-exposure three animals, although asymptomatic, hadAChE levels that suggested persistentAChE inhibition. At 77 days following initial exposure, AChE levels were within normal limits.
Blister beetle poisoning (cantharidiasis) of horses has been well documented. Primary exposure to blister beetles is through consumption of contaminated lucerne hay. Confirmed cases of bovine cantharidiasis due to natural exposure have not previously been documented in veterinary literature. This report describes four cases of blister beetle poisoning in three dairy herds and one beef herd in New Mexico and Oklahoma, USA, that were reported between 1995 and 1999. Cows in two large dairy herds consumed blister beetles in a total mixed ration containing green chop lucerne. The most significant clinical signs were mass refusal to eat the freshly cut green chop lucerne, although the cows appeared hungry, and the corresponding dramatic decrease in milk production. Cows in a smaller dairy herd and a beef herd consumed large round bales of lucerne hay containing blister beetles. In contrast to cows exposed to the beetles in green chop, feed refusal in these cases was limited to individual cows. Other clinical signs included salivation, bruxism, frequent urination, diarrhoea, reluctance to move, abdominal pain, ataxia and recumbency. Postmortem examination did not reveal significant gross or microscopic lesions. Cantharidin was detected by gas chromatography-mass spectrometry analysis of either urine or feed samples. In addition, blister beetles were found in the lucerne green chop or hay.
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