LARGE scale sheep producer Martin Flower says copper deficient pastures could be silently robbing wool growers and lamb producers of valuable yield.
Mr Flower, who manages the ASX-listed Duxton Farms' Naracoorte operation near the South Australian-Victorian border, is urging producers to be more vigilant around the signs exhibited by sheep deficient in copper from pasture-fed diets.
"It's not always clearly visible in your flocks; for us it became apparent in the feedback we were receiving from our abattoirs," he said.
"That's what caused us to investigate further to have the problem addressed."
Before selling the Naracoorte property to the Duxton Farms Limited investment group in 2018, Mr Flower owned the 2000-hectare aggregation for 27 years, bearing the Boorala name still used to this day.
Located in a highly productive, reliable farming region, Boorala is a mixed sheep and cropping enterprise, comprising 60 per cent grazing dryland country receiving 525 millimetres average yearly rainfall.
Pastures are a mix of perennial species, comprising phalaris and ryegrass with a sub clover base.
Pastures can last 10-15 years, with some even pushing beyond 20 years, depending on the persistence of perennial grass species.
"When paddocks start thinning out of perennial grasses, they normally go back into a cropping rotation phase," Mr Flower said.
"And when the cropping paddocks start getting too dirty with grasses, they go back into a pasture phase."
Depending on weed numbers and available feed on offer during the season, pastures can receive a broadleaf weed spray.
"Insecticides are rarely used on Boorala pastures," he said.
"If pastures do require a red legged earth mite spray, we try to follow the trimerite program of spraying in the spring time."
Fertiliser rates for pastures are calculated on Dry Sheep Equivalent (DSE) per hectare.
Working on 0.8 units of phosphorus (P) per DSE, P levels are maintained at a range of 40-50 Colwell P.
"If phosphorus levels drop below this range, we would normally up our DSE rate of P to 1.3-1.6, depending on the budget," he said.
Mr Flower's carefully-managed pasture program supports a flock of 5000 F1 Merino/Border Leicester breeding ewes, with female progeny mated to Poll Dorset rams.
In an average year, Boorala will turn off more than 6000 lambs to JBS.
In 2005, when Boorala was under his ownership, Mr Flower received feedback from processor, Tatiara Meat Company, now owned by JBS, that consigned lambs post slaughter were exhibiting brittle ribs that were highly susceptible to cracking during deboning.
Mr Flower estimates that in carcases with cracked ribs he was losing between one and two kilograms of meat per beast.
"We haven't put an exact dollar figure on what we were losing, but even if you calculate a loss of 1kg per carcase at say $9/kg over 6000 lambs that we send to slaughter each year, it soon adds up," he said.
Further investigation and consultation with his technical agronomist, James Stewart, Hamilton, Victoria, isolated the cause as copper deficient soils.
Formerly with Vickery Bros and now with Incitec Pivot Fertilisers, Mr Stewart said the first steps in the investigation involved identifying paddocks where ewes were joined the previous year, and soil and tissue testing paddocks with an absence of any recent soil test history.
"This process definitely confirmed the paddocks with the problem," he said.
"As added assurance, we also advised Martin to get a liver biopsy done on an older ewe.
"Everything confirmed there was a problem, so copper was added to the pasture fertiliser the following year."
To achieve efficiency gains and maximise value from the added cost of the copper, calculated at an extra $20 per hectare, Mr Flower divided the farm into thirds, applying a capital rate of copper at 1kg/ha onto each third annually, so that the whole operation was covered after three years.
Meat & Livestock Australia estimates copper deficiency could be costing southern Australian sheep producers more than $15 million a year.
It can also cause slow animal growth rates, reduced wool quality, sway back or lack of muscle coordination in lambs, scouring, lameness and infertility.
"We didn't notice any other outward signs of poor health in our sheep while they were on the ground," Mr Flower said.
"It was only the feedback about the cracked ribs that got us investigating copper deficiency problem.
"Since we've addressed the copper issues on our grazing country the cracked ribs have decreased dramatically.
"I'd say it's down from 25pc to 10pc in the first five years and now down to about 3pc of our lambs in the last year.
"We continue our soil and tissue testing program every year and keep an eye on our copper levels."
Mr Stewart said addressing copper deficiency isn't always straightforward and most producers would need the guidance of a trained agronomist backed by soil and tissue tests to assess nutrient levels.
"Even if you are not in a known copper deficient area, you should understand the mechanism of both primary and secondary deficiency," he said.
"Primary copper deficiency occurs when a soil with low copper levels produces a pasture with low copper levels and therefore the sheep also have low levels.
"Secondary deficiency occurs due to the antagonistic relationship of copper with other nutrients such as molybdenum, sulphur and iron, which can all reduce the availability of copper to animals by forming insoluble complexes.
"They can act alone or in combination.
"This means graziers who are improving the productivity of their pastures - by liming or lifting phosphorus fertility or applying molybdenum - may be inadvertently reducing the copper available to their sheep.
"A lot of lamb producers these days are topdressing nitrogen to their pastures prior to lambing, or in the spring for hay and silage.
"They should be mindful that nitrogen can induce copper deficiency in the plant also."
