More than 1,000 chickens were killed after the lorry transporting them crashed on the M62 this morning.
About 6,800 birds were packed into crates that flew from the vehicle on to the carriageway when it hit barriers at the side of the road.
Many died from the impact of the crash but others escaped on to the motorway, where some were run over.
Officers from the Highways Agency, police and RSPCA tried to herd 2,000 chickens to safety in a nearby field as they ran around the carriageway.
Michael Clarke, from the agency, told the BBC: “The more adventurous ones did manage to go quite far - I would suspect there are a handful still in adjacent fields.”
Some of the chickens reportedly found their way into the cars of queuing motorists who had wound down their windows amid the confusion.
Part of the motorway was closed near Eccles between junctions 11 and 12 shortly after 4am.
A spokesman for Greater Manchester Police said no other vehicles were involved in the accident and the lorry driver was not seriously injured.
The motorway was closed eastbound while the debris was cleared but has now fully reopened.
A spokesman for animal charity Peta said the incident exposed the “extraordinary trauma and cruelty of transport for chickens” and other animals.
“Chickens are routinely crammed by the thousands onto the back of lorries and taken on terrifying journeys to slaughter in all weather conditions,” he added.
“Peta will be asking to place a memorial sign for the chickens who died in the lorry crash near Warrington this morning.
“We hope our memorial will remind people that chickens are not just body parts to pick out of buckets but individuals with feelings who, like us, don't want to die in an upturned lorry or at an abattoir.”