Sixty cattle can be released into a 262-hectare site in the Wonnangatta Valley in the first year of the program, which the Napthine government says is necessary to test whether grazing reduces the risk of bushfires by removing fuel loads.

Critics say past research has shown cattle grazing does not stop bushfires and damages sensitive alpine ecology, and the trial lacks scientific rigour.

As Premier Denis Napthine said he welcomed the approval of the trial - proposed in different forms since before the 2010 election - the opposition immediately vowed to overturn the decision if it won the November election.

Mountain Cattlemen's Association of Victoria president Charlie Lovick was overjoyed and relieved at the decision, which he said was a chance for the cattlemen to ''demonstrate their own conservation credentials''.

''I've been waiting for this day for so long - since we were unceremoniously kicked out by [former federal environment minister] Tony Burke, with his purely green intentions. And every year that we've been out of the bush I feel for the bush, because I know it's getting closer to destruction,'' he said.

Mr Lovick said the cattlemen planned to jointly drive their cattle for the last 60 or so kilometres over the mountains and into the trial location. He hoped they would graze in the valley for four to six weeks this season.

He called on environmentalists who objected to high-country grazing to stand back and let the ''well-designed'' trial occur.

University of Melbourne ecology professor Ary Hoffmann, a fellow with the Australian Academy of Science, said the trial was scientifically flawed and was likely to do unacceptable damage on a national heritage site and threatened species in the park.

''It ignores an awful lot of research that shows that cattle grazing has detrimental effects on biodiversity and would have no impact on fire,'' he said.

Professor Hoffmann said there was growing concern over the lack of respect for science in policy decisions.

Mr Hunt stressed that the trial would initially be conducted over a much smaller area than the proposal blocked by the Gillard government, but Professor Hoffmann said it was still in an area deemed worthy of a national park.

''There are areas out of the park that could be used for this purpose,'' he said.

The trial may be increased to 300 cattle in its second and third year subject to approval from Mr Hunt.

Victorian National Parks Association spokesman Phil Ingamells said it was a farce. ''The same thing can be easily done outside the national park, but this option was not even considered,'' he said.

With Henrietta Cook