Welfare officers and farmers have welcomed new laws which are aimed to stamp out fly-grazing.
Horses can be left in terrible conditions or cause damage to crops and fences after being dumped illegally or tethered to one spot by irresponsible owners.
But the Control of Horses Act came into force on Tuesday and gives greater power to landowners.
Previously landowners had to wait 14 days to dispose of the horses through a sale or auction.
Thanks to new laws, landowners can immediately take the horses to a place of safety, notifying police within 24 hours. If no owner is identified within four working days, the horses can be sold or re-homed to charities.
Field officer for World Horse Welfare in West Norfolk, Jacko Jackson, has welcomed the new act.
He says 25 per cent of his workload is down to fly-grazing and has recently rescued three mares from a field in Stoke Ferry, which were found with bones.
Mr Jackson said: “It is a major problem across Great Britain. Some of these people will knock down a fence and put their horses in a field.
“It is not too bad at this time of year providing they move the tether but problems start occurring when the animal can’t reach food and water. A lot of these horses don’t have access to water.
“They also have a worm burden as they are eating and defecting in one area.
“Quite often under the old act, they would wait until the landowners have put the horses up for action and buy them back for a fraction of the price.
“We hope it will deter people from doing it.”
The worst case he had seen was 30 horses dumped in Thetford.
Mr Jackson said: “People need to be aware that the law is changing and this puts another tool in the box of organisations who deal with these things.”
World Horse Welfare along the CLA and NFU have been campaiging for changes.
CLA East Regional Director Ben Underwood said: “Fly-grazed horses can damage land, crops and fencing, restrict space for livestock and cost money to provide for their welfare and safety. It has been very difficult, time consuming and expensive for landowners to deal with these situations but from Tuesday they can take swifter action to resolve the problem by, for example re-homing the horses to charities or privately.”
Chairman of Downham and District NFU branch Ed Lankfer has also welcomed the new law.
He said: “It can’t be a bad thing if we can sell or re-home these horses. Flytipping is a problem.”
The bodies of three horses were seen floating in the drain near Marshland St James earlier this week.
Middle Level Commissioners paid for the removal of two bodies. One had sunk.
The drainage board’s John Fenn said: “People should take responsibility for their animals whether they are alive or dead. This is not the best use of rate payers’ money.”