It is believed the man was standing alongside the moving trailer, feeding hay to sheep when he was knocked to the ground about 9.30pm on Monday.
The trailer was attached to a ute.
WorkSafe is investigating.
The fatality brings the number of confirmed workplace deaths this year to ten, and is the sixth to occur on a farm.
WorkSafe Acting Executive Director Health and Safety Paul Fowler once again urged farmers to put safety first.
"Tragically, many on-farm fatalities involve people doing tasks they have done many times before, but experience doesn't prevent injuries or deaths," he said.
"WorkSafe is urging farmers to think about the tasks they do each day and whether they can be carried out more safely, for their own sake and the sake of their loved ones."
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