NSW MLC Mark Pearson has backed a program, piloted with mustangs in the United States, where wild horses are shot with a dart containing a PZP vaccine.

The drug makes a horse sterile for two years, and a second shot after that period generally makes them unable to reproduce for the rest of their life.

The Animal Justice Party politician met with environment minister Mark Speakman last Thursday to lobby for the measure, blasting any “Rambo operations” to control populations.

“We brought them here,” Mr Pearson said. 

“They certainly shouldn’t have to suffer just because they have been able to breed with no natural predator.”

In May, National Parks and Wildlife Service unveiled a draft plan to substantially increase brumby cull and removal programs from Kosciuszko National Park.

The plan proposed to reduce the current population from 6000 to 600 in 20 years.

Despite community outcry that the plan would sign the death warrant of an Australian icon, more than 40 scientists backed the plan by sending an open letter to Premier Mike Baird in August.

The academics, led by Deakin University ecologist Don Driscoll, advocated that the draft plan be completed in a quarter of the proposed time and include aerial shooting, which has been outlawed in NSW since 2000.

Wagga anti-cull campaigner and brumby owner Helen Day previously  estimated at least 200 brumbies have been culled between June to the end of July.

A Department of Environment and Heritage spokesperson said over 900 submissions on the draft plan had been received, with methods such as fertility control being considered. 

A final decision will be announced later this year, the spokesperson said.