Minister for Agriculture David Littleproud announced the new definition change today, which he said would remove NZ producers “unfair advantage”  over Australian farmers.

Australian lamb had been considered to have grown into the less lucrative “hogget”, or mutton, as soon as incisor teeth were visible.

The NZ definition classifies an animal as a lamb even after two incisor teeth had popped through.

That enables slightly-older sheep, which are typically in good condition, to be sold under the more profitable lamb name.

“Lamb will continue to be called lamb when the animal has two permanent incisor teeth, so long as those teeth are new and have not begun to wear,” Mr Littleproud said.

“Our export definition will now match New Zealand’s definition and our own new AUS-MEAT definition.

“After decades of discussion, the time for talk was over. This is a simple common-sense change.”

Mr Littleproud said the new definition would allows Australian growers to sell more lambs towards the end of the growing season and expand their export opportunities.

“It will be easy for growers to see when a lamb becomes a sheep – when there is visible wear on the incisors.”

The change will require amendment to the Export Control (Meat and Meat Products) Orders 2005, to change the definition of what constitutes lamb.

Research by Meat and Livestock Australia found no discernible difference in eating quality between lambs immediately prior to incisor teeth and immediately afterwards.