Gatecrashers to a party at the Moree Racecourse on Saturday night released Bleue Pepite from the stables after being refused entry.

Bleue Pepite cut its leg just below the knee, forcing the trainer to withdraw the horse from a $10,000 race being held the next day in Coonamble.

Bleue Pepite and another Sinclair-trained horse, Joppick, ran around the carpark before they were caught by one of the people at the party.

Mr Sinclair said the two horses were loose for up to an hour, which is when Bleue Pepite suffered its injury.

"She must've run into something when she was running around," he said.

Mr Sinclair said he had a good idea who the culprits were, but didn't want to name names.

"It was just some undesirables who turned up and weren't invited."

Mr Sinclair also said he knew the people who had hosted the party and was sure they would have felt bad about the incident.

Letting the horses loose was a cowardly act by the gatecrashers, Mr Sinclair said.

"It wasn't the horses who put them out of the party. If they were brave enough they would've done it to the people not the horses."

Retired jockey Danny Frahm said it wasn't the first time people had let horses loose from the Moree Racecourse.

He said the solution to the problem was simple - locks and fencing.

"It's a common sense thing. They've got to put those 2m-high fences with the barbed wire," he said.

"[The racecourse has] got to have the fences there, but you can't have the fences unless the horses are secure."

Mr Frahm said fencing wasn't only needed to protect animals that could be worth up to $30,000.

He also said it was necessary to stop unscrupulous characters doping horses.

He said if someone wanted to, there was nothing to stop them sneaking into the stables and secretly drugging horses. The trainer would then be held responsible for the positive drug test, which would mean a fine or suspension.

"Anybody can go in there. You just go through the gate," he said.

Mr Frahm also pointed out the possible consequences had Bleue Pepite and Joppick wandered onto the Newell Highway and caused an accident.

Death, injuries and legal action would all have been possibilities, he said.

"It could've been a lot worse," he said.

"You've got to be able to leave the place and know your horses are secure," he said.

"I think it would be money well spent if they put in suitable security fences.

"It's something that needs doing, I reckon. It will benefit everybody all around."

The Champion was unable to contact anyone from the Moree Racecourse Trust.