Drought-stressed sorghum crops could poison cattle and sheep, the NSW Department of Primary Industries warns graziers.
DPI Feed Quality Service (FQS) analytical chemist Richard Meyer said nearly half of sorghum samples received this year contained dangerous levels of prussic acid (hydrogen cyanide), which could poison or even kill stock.
Drought-stressed, stunted sorghum, millet, and Sudan grass plants produce prussic acid during drought and after rain.
“If livestock safety is in doubt, we advise producers test plants that commonly cause prussic acid poisoning before stock graze risky feed,” Mr Meyer warned.
Producers should only allow stock to graze sorghum more than 50 centimeters high, and feed hungry stock hay before grazing forage that could contain prussic acid.
Producers should cut sorghum hay during low-risk conditions, as prussic acid content survives the hay-making process.
While silage production can reduce toxin levels of prussic acid by up to 50 per cent after three weeks, Mr Meyer recommended that producers test all fodder produced from susceptible crops before feeding sheep and cattle.
Symptoms of prussic acid poisoning are similar to nitrate poisoning: respiratory stress, muscle tremors, and staggering.
Prussic acid toxin combines with haemoglobin to turn blood cherry red, while nitrate toxicity turns blood chocolate brown.
Producers can send samples to the DPI FQS laboratory for testing, and should consult their vet if they suspect prussic acid poisoning.
More information about prussic acid poisoning is available from the DPI.