Southland farmer and his dog to represent NZ

The trans-Tasman rivalry has reignited once again - this time in the search for the hardest working farm dog.

It's the first time New Zealand has entered the Cobber Working Dog Challenge, which tracks how hard each canine works over the three-week competition using GPS collars.

One duo representing the country is Josh Tosh and Trix - from Dipton in Southland.

Tosh told Morning Report he has had Trix since she was just 8 weeks old and has trained her up to the hard working 3-and-a-half year old farm dog that she is now.

"She's definitely a special dog to me, she's a fully broken Heading Dog and she's born and bred in Southland... she'd be the dog I use for about 80-90 percent of my work on the farm and she's just a bouncy ball full of energy," Tosh said.

"I can't tire her out at all and it's just because she loves her job she loves what she does ... she's my best friend really."

He said even after working a 14-hour work day Trix is keen to have another run.

In the first day of the competition on Monday, the New Zealand Heading Dog ran just over 40kms while mustering, Tosh said.

There's no set strategy in place to get the most out of Trix but Tosh said he's confident about their odds in the competition.

"I think our chances are pretty good to be honest, I hope team kiwi can beat the aussies.

"Strategy wise I'm probably just going to do what I do day-to-day really I don't think we're going to change anything special and make them run further because that's kind of bending the rules.

"I'd rather just do what we do and then if we manage to win we manage to win and it's just also going to be really interesting to see what our dogs are actually doing over that time," he said.

There are 12 dogs competing in the competition with two other Heading Dogs repersenting New Zealand - four-year-old Pine from Canterbury and three-year-old Spark from Otago.

The competition comes to a close on 5 September and the leaderboard will be updated as the event goes on.