An animal welfare group is calling on the Department of Conservation to fast-track trials of a reproductive vaccine that could do away with the annual Kaimanawa muster.
Last year, the Department of Conservation (DoC) rounded up more than 200 of the country's only wild horses, as part of its effort to bring the base herd down to 300.
The cull is set to take place again in late May or early June.
Kaimanawa Wild Horse Welfare Trust chairperson Elder Jenks says DoC should be using a new vaccine developed for deer in the United States to reduce the fertility of mares.
DoC analyst Bob Fleury says the department is looking at holding a trial in conjunction with Australia.