Reducing the risk of ergot poisoning of feedlot cattle

Summary

Sorghum ergot is a fungal disease with the potential to affect a large proportion of Australia�s sorghum crop. Studies showed that feedlot cattle were very sensitive to sorghum ergot alkaloids, mainly represented by dihydroergosine (DHES). Depressed feed intakes and growth were measured in Hereford steers given feed containing ergot and these effects were most pronounced during hot, humid weather, when affected animals were apparently unable to dissipate heat and showed signs of severe heat stress.

The tolerance was < 1 mg/kg (1ppm) of alkaloid in the feed. Rye grass ergot (main alkaloid ergotamine) is also of concern to lot-feeders, as it regularly contaminates wheat and barley crops in southern states and has been associated with mortalities in cattle, eg in WA, at Forbes in late 1999, and in SA in 2001. As with sorghum ergot, the effects of rye ergot greatly increase susceptibility to heat stress. Both sorghum and rye ergot sclerotia vary greatly in alkaloid content, and good analytical methods are essential if tolerances are to be firmed up, and feed-monitoring regimens implemented.

To reduce the risk of ergot poisoning in feedlots, this project investigated means of physically identifying those ergot sclerotia that might contain high concentrations of alkaloid, and whether physical segregation by grading could remove all of the alkaloid from contaminated loads. The project also aimed to develop rapid tests for ergot alkaloids. Effectiveness of Near-Infra-Red Spectroscopy for detecting ergot alkaloids. A previous study supported by MLA (FLOT.115) evaluated Near Infra-red spectroscopy (NIR) for detecting ergot alkaloids, as this could potentially allow very rapid screening of grain samples.