North Coast dairy farmer Robbie Gordon checks feed from the mixer wagon with DPI Regional Animal Health Leader Paul Freeman. Botulinum toxin in silage feed killed 98 of Mr Gordon's dairy cattle.

Robbie Gordon wouldn’t wish his last few weeks on anyone.

The dairy farmer from Grevilia, near Kyogle on the North Coast, has watched helplessly as 98 of his dairy cows have died from botulism by eating contaminated silage.

While the tests are not conclusive, it seems a small animal or snake may have died and rotted in the stored silage, producing the potent botulinum toxin.

"The vets told me there’s nothing you can do once the cows are affected, just watch them die - it’s absolutely devastating," Mr Gordon said.

"I still can’t sleep. I wouldn’t wish it on anyone." Mr Gordon said he wanted to "shout from the highest mountain" about the importance of vaccinating cattle against botulism.

"We had been vaccinating but, what with the drought and everything, it slipped off the agenda.

"I’ve spoken with other people, who like me, haven’t vaccinated their cows for one reason or another.

"They’ve been lucky - but if you’re unlucky like we were, the impact is devastating.

"Anyone who is feeding silage to beef or dairy cattle should have them vaccinated against botulism.

"The cost at about $1.50 a head is nothing compared to the possible consequences." Mr Gordon said he would never forget the day his cows started to go down.

"I went to get the cows from the feed pad and one looked a bit crook with what I thought might be three-day sickness," he said.

"Two stopped under the bridge on the way to the paddock, and five went down at a water trough.

By dark that day there were seven dead.

"The vet told me to change the feed, which I did, but by 5am the next morning there were 25 dead."

Two weeks later 98 of the 117 cow herd had died.

Support from family and friends in the dairy industry and local factory Norco had been "fantastic", Mr Gordon said.

There had been offers of cash donations and replacement cows.

This is being co-ordinated by Norco and NSW DPI through the Far North Coast Dairy Industry Group.

"It’s going to be hard, but with the support we are getting, we hope to rebuild our herd and start milking again one day," he said.

NSW DPI regional animal health leader, Paul Freeman, said this was the second major botulism outbreak on the North Coast in the last decade.

In 2000, 114 dairy cows died when they ate contaminated silage.

He said botulism was a disease that could occur in cattle when feed was contaminated with botulinum toxin produced by bacteria growing in rotting animal or vegetable material.

"Sources of rotting material in stored silage have in the past included snakes and other animals," he said.

"These animals are sometimes killed by slashers and incorporated inside large round bales or pits of silage."

Mr Freeman said signs of botulism in cattle varied from sudden death to a slowly progressive paralysis where animals might take days to die.

"Once cattle go down their recovery is unlikely," he said.

Vaccination is a cost-effective method of avoiding a botulism outbreak.

"Beef and dairy producers who feed their cattle a prepared ration, especially those based on silage, should vaccinate their animals against botulism well before the feed ration is introduced," he said.

Anyone wanting to help Robbie and Christine Gordon and their family can contact Col Griffiths at NSW DPI, Kyogle, on 02 6636 1900, or Tim Kirk at Norco on 02 6627 8141.