The two adults and child were trapped inside the car when the wreck was found on the Gwydir Highway about 11.15am today.
The child has been taken by NSW Ambulance for further assessments, while the truck driver was treated by paramedics for minor injuries.
Multiple cows died at the scene and many others had to be euthanised.
NSW Police have closed the Gwydir Highway is closed in both directions at Matheson.
Read Related Also: Liz Cheney promises to leave the Republican Party if Trump is the nominee in 2024
“Eastbound traffic from Inverell is being diverted via Bundarra Road to Gilgai, Guyra Road to Guyra, and New England Highway to Glen Innes,” NSW Police said.
A NSW Transport Management Centre (TMC)spokesperson said Westbound traffic was diverting via the reverse route and the diversion was suitable for all vehicles.
“Motorists using this diversion should allow about an hour extra travel time and follow the directions of emergency services and traffic crews,” TMC said.