The Subtropical Dairy program is warning farmers in northern drought-affected areas to be aware of the risks in feeding stressed or stunted sorghum crops to animals.
The warning also applies to feed hays made from these crops.
According to this Queensland Government website, cyanide (sometimes called prussic acid) and nitrate can be present in various amounts in grain and forage sorghums.
"In hot and dry conditions, such as drought, these plants become stressed, causing them to accumulate these toxins," it said.
"Fatalities can occur where ruminants graze sorghum crops or are fed sorghum hays containing excess levels of cyanide and or nitrate toxins."
Signs of cyanide poisoning in animals include:
Signs of nitrate poisoning in livestock are similar to cyanide poisoning and include:
The website warns that animals eating large amounts of toxic feed die within 5–15 minutes of developing clinical signs of poisoning.
"Affected animals rarely survive more than 1–2 hours after consuming lethal quantities," it said.
Samples of suspect crops and hay can be sent to labs for testing before feeding out.
There is a 1-2 day turn-around-time for cyanide testing after the sample is received at the laboratory.
The cost of sample processing and testing is about $80 per plant sample.
The website said the following guidelines for using sorghum crops as fodder can help reduce the risk of cyanide and nitrate poisoning:
More information about prussic acids and grazing affected crops can be found on this Queensland Government website this Queensland Government website and this NSW Primary Industries website .