Fodder crop warning

Prussic acid warning on sorgum - feed tests, caution urged


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Department of Primary Industries feed quality service analytical chemist Richard Meyer says great care must be taken when dealing with stressed forage sorghum crops.

Department of Primary Industries feed quality service analytical chemist Richard Meyer says great care must be taken when dealing with stressed forage sorghum crops.

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Half of the forage sorghum crops in NSW could be potentially fatal to cattle and sheep if grazed at the wrong time.

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AS MUCH as half the state’s sorghum crops could potentially be poisonous, with alarming feed test results by the Department of Primary Industries revealing high levels of prussic acid.

DPI feed quality service analytical chemist, Richard Meyer, said close to 50 per cent of sorghum samples received this year had significant levels of prussic acid, which could cause serious poisoning and death if grazed by stock.

“Prussic acid, hydrogen cyanide, is produced by sorghum, millet and Sudan grass during drought and following rain, when drought-stressed, stunted plants begin to grow,” Mr Meyer said.

He said producers should never allow stock to graze sorghum less then 50 centimetres high, and hungry stock should be fed hay before grazing forage that could contain prussic acid.

Mr Meyer said fodder should be tested, otherwise producers could find themselves on shaky ground, putting their stock at risk. He said producers should ensure sorghum hay is cut during low-risk conditions as prussic acid content survives the hay-making process.

Elders agronomist Benjamin Romeo, who works between Orange and Forbes, said the season had created a lot of stress events for crops, and that was when prussic acid levels, and nitrate levels, tended to soar to dangerous levels. “Prussic acid is cyanide, they can be dead in a couple of hours, they don’t come back from it,” he said.

“It’s really something you have to be very mindful of when you’re chasing feed.

“You need to put them in with a full belly and wean them onto the paddock.

“And a sulphur lick, while it can help mitigate risk, is certainly no cure,” he said.

Mr Romeo also warned of the dangers of cutting hay or silage if a crop was stressed.

Farmers could find themselves stacking poisonous fodder in the shed if they weren’t careful, he said.

“Silage production can reduce toxin levels of prussic acid by up to 50 per cent after three weeks, but we recommend all fodder produced from susceptible crops is tested,” said the DPI’s Mr Meyer.

Symptoms of prussic acid poisoning are similar to nitrate poisoning with respiratory stress, muscle tremors and staggering.

Prussic acid toxin combines with haemoglobin to turn blood a notable cherry red colour, while nitrate toxicity turns blood a chocolate brown colour.

Producers can send samples to DPI FQS laboratory for testing, https://www.dpi.nsw.gov.au/about-us/services/laboratory-services/feed-quality-service and should consult their veterinarian if they suspect prussic acid poisoning.

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