Agriculture Minister Bridget McKenzie has offered 100 vets to bushfire-affected states to assess and euthanase thousands of injured livestock.

Senator McKenzie fears the bushfire crisis could devastate the national herd, with animals dying from heat stress and smoke inhalation.

Defence personnel will be sent into fire grounds once it is safe to dig pits and bury dead stock.

"Bearing in mind, though, it's about getting access to those still live fire grounds," Senator McKenzie told the ABC.

"Where it's safe to do so we need to be getting in within a week, ideally, to really be dealing with the carcasses in an appropriate way."

The National Farmers' Federation estimates thousands of sheep and cattle have been killed in the bushfires.

The livestock toll is expected to climb after fires tore through southern NSW over the weekend, with dozens of dead livestock seen lining the road into Batlow.

Fodder and water is being distributed to surviving livestock herds on blackened paddocks, while fencing and other farm infrastructure is repaired.

Water stocks contaminated by ash are also being investigated.

Emergency Management Minister David Littleproud said disposing of dead livestock was an urgent task.

"We will be trying to take pre-emptive steps today with state agencies around making sure the disposal of the livestock is done quickly - there is a biosecurity risk there," Mr Littleproud said.

"We have to think about our native species that have been decimated by the fires, too, in terms of our recovery."

Senator McKenzie paid tribute to farmers dealing with sick and dying stock while fighting the ongoing fires.

"We're looking at very stretched, superhuman efforts here by our agriculture sector," she said.

Farming organisations have also asked for fodder and water, but bringing hay into communities could increase the fire danger.

The federal government has committed $2 billion over two years to a national bushfire recovery fund.

The fund will support local governments, farmers and primary producers, and deliver mental health supports.

Scott Morrison has pledged to commit "everything that is needed and more" to the recovery effort.

"If more is needed and the cost is higher, then more will be provided," the prime minister told reporters.

The states will not be asked to match the federal government's funding.

The recovery fund will be administered by a new agency headed by former Australian Federal Police boss Andrew Colvin.

The prime minister said his government was not focused on the financial cost.

"The surplus is no focus for me," Mr Morrison said.

"What matters to me is the human cost and meeting whatever cost we need to meet."

Reconstructing bridges, roads and critical infrastructure destroyed by the blazes is expected to cost hundreds of millions of dollars.

The prime minister is considering launching a royal commission into the bushfires, an idea which opposition leader Anthony Albanese is open to.

"We're going to have to have a comprehensive inquiry that goes to the full suite of measures," Mr Albanese told Sky News.

"How we manage our national parks, the long-term impact of climate change, this is not business-as-usual."

Australian Associated Press