Glenlyon Jill clocked up an impressive 64 kilometres in only half a day of testing. By comparison, the marathon run at the Tokyo Olympics was just 42 kilometres.

From Monday, August 16, a dozen working dogs from around Australia and New Zealand will be tracked over three weeks to chart their endurance in the Cobber Challenge.

A GPS will be fitted to Jill's collar and that of the other competitors to find the winner.

Mr Leahy and his dogs work on several farms on the slopes of the Great Dividing Range in Victoria's high country, east of Seymour.

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Just a year out of school, he already has a team of seven dogs, though three of them are from Jill's litter earlier this year.

"You can't run stock on this country without dogs," Mr Leahy said.

"They can get to places in the nooks and crannies of this sloping, granite country that I can't on the motorbike.

"The dogs are worth two to three workers."

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Mr Leahy works with prime lambs and black cattle on his own family property, but he also works on neighbouring properties like Tarcombe Herefords.

He said two-year-old Jill was a star.

"She understands what to do without commands. She casts wide and keeps them [the stock] bunched tight while still keeping them in motion."

Mr Leahy said he entered the Challenge because he was fascinated to learn how far his dogs range.

"They travel long distances but also up some pretty steep country as well," he said.

His only worry for Jill is that she is injury-prone. She is not allowed a free ride on the motorbike because of previous mishaps.

He fuels his crew on dry food, mutton and even venison occasionally.

"I reckon Jill will do pretty well but I think her competition will come from those New Zealand dogs which also cast wide and travel a lot of hilly country," Mr Leahy said.