Nicholas Cole, 47, pleaded guilty to dangerous driving following the incident in July 2023 between junction 14 and 15 of the motorway in Northamptonshire.
Northants police said National Highways had closed lane one due to a broken down horsebox.
However, despite a red X gantry sign and a parked highways vehicle behind the horsebox with flashing amber and red lights, Cole failed to move out of the lane.
At the last moment, he attempted to steer his lorry out of the path of the stationary vehicles, but he clipped the Highways vehicle and crashed into the horsebox.
The driver and passengers were waiting on the bank and were unharmed, but their horse was killed in the collision.
Cole claimed he had been listening to the radio before the collision and that the next thing he knew he saw the Highways vehicle and swerved to avoid it.
He was sentenced at Northampton Crown Court to 42 weeks in prison and suspended from driving for 21 months.
PS Richard Hill from Northamptonshire Police’s Roads Policing Team said: “This was a shocking collision that sadly resulted in a horse being killed.
“It’s a stark example of how important it is to keep your focus on the road when you’re driving and to ensure you read the gantry signs displayed on the motorway. Cole would have had plenty of time to see the red X and yet still caused this collision.
“I hope this sentence is a lesson to him and to other road users. Driving a vehicle is a big responsibility and it is paramount that you are always aware of your surroundings.”
