Already the second largest organic lamb producer in Australia, it turned off 23,000 Dorper lambs last year and aims to at least double its 18,000 breeding ewe numbers within three years - mostly to satisfy US export orders.

Tandou is also targeting a big improvement in weight gain rates to lift its production efficiency.

Dorpers already enjoy a reputation as hardy, wide-ranging foragers with good fertility rates, but Tandou's pastoral manager Paul Martin wants to get his flock genetics capable of producing 45 kilogram lambs at six months.

"They seem to be the best converters of dry matter to protein I know of - even when conditions are dry," he said.

"We're still two or three years away from getting breeding stock capable of producing lambs which achieve daily weight gains of 170 to 225 grams a day in our environment, but we're doing a lot of testing and culling to select for genetics with good conversion rates.

"When we had plenty of clover growth our lambs were getting 300g/day, but we know pasture conditions will often be more like the past year (just 48 millimetres since last March)."

Tandou, which ran as many as 28,000 Merinos in the mid 1990s before opting for lower maintenance Dorpers a decade later, has initiated a major fencing and yard building program to contain its expanding meat sheep flock.

They run at a conservative stocking rate of one sheep to 7.8ha on 113,200ha at Tandou's main Menindee pastoral operation, and on leased Ivanhoe properties "Paddington and "Keewong".

"You don't have to shear them, or worry about drenching out here, but good fencing is a major issue with Dorpers," said Mr Martin whose team spent about $500,000 upgrading fences in the past year.

Lambs are sent to SA meat processor T and R Pastoral to service a fast growing US trade, and the Arcadian Organic Meat Company at Junee, a major supplier to Woolworths.

"T and R's doing a massive job trying to grow the market in the US - it's very promising," Mr Martin said.

Tandou's livestock business also includes a beef herd of 1200 predominantly Angus and Hereford blood young cattle, mostly bought in weighing around 225 kilograms and turned off at 450 to 480kg (liveweight).

About 10,000 goats and 1200 pigs were also trapped (or shot) and sent to slaughter from the Menindee and Ivanhoe properties last year as part of a campaign to reduce feral grazing pressures on the landscape.