Don’t shrug off shrubs

Frank SmithCountryman

Using native shrubs to supplement sheep and cattle feed can add 15 per cent to the average farm bottom line.

That was the conclusion of a six-year research program, titled Enrich, run by a consortium of CSIRO, state departments of agriculture and grower groups.

The first of six countrywide forums was held in Merredin recently, with a follow up at Mingenew.

Dean Revel of CSIRO said the MIDAS whole farm model showed an optimum area in shrubs of about 15 per cent.

“Half the benefit is due to saving on supplementary feed during the autumn feed gap and the rest because shrubs allow better management of annual pasture,” Dr Revel said.

“Other benefits include improved nutrition from a range of dietary sources, reduced soil erosion and salinity control.

“If you increase the proportion of shrubs by more than 15 to 20 per cent, you begin to lose cropping land and hence profitability.”

Perennial shrubs extend the grazing season. Although shrubs are not as productive as annual grasses, they provide digestible energy in autumn, when it is most valuable and allow farmers to defer grazing in autumn and allow other pastures to grow.

Dr Revel said most shrubs responded to summer rain. He said summer rain in the Wheatbelt was an all-or-nothing event and, without perennials, the rain was usually wasted.

“Many shrubs struggle or don’t persist under grazing. We are not recommending wall-to-wall shrubs, just adding shrubs as a component in mixed pasture,” Dr Revel said.

Other advantages of shrubs include shade and improved gut health.

Shade has a massive impact, especially on young animals. Sheep can use from 10 to 20 per cent of their energy intake just maintaining body temperature.

Phil Vercoe of the University of WA School of Animal Biology said shrubs supplied more than just energy and dry matter.

“Shrubs are a value package — not just a source of energy. They provide crude protein minerals and bioactive compounds,” Professor Vercoe said.

“A diverse forage system is of value to the rumen. Think of the rumen as a black box containing a dynamic microbial fermenting soup. Its output comprises energy, microbial protein, methane and ammonia.”

Methane and ammonia are waste products and greenhouse gases. Up to 10 to 15 per cent of feed energy is wasted as these gases.

“We need to find food components that reduce methane production, but not fermentability. These have been bred out of usual pasture plants,” Professor Vercoe said.

“We have screened 150 plants. On average, there is a linear relationship between methane output and fermentability but there are a few outliers that exhibit high fermentability and low methane production, giving scope for selection. There is also variation within species.”

Bacteria that break food down to methane live on the surface of protozoa in the rumen. Some shrubs contain bioactive substances that reduce their numbers.

One shrub that reduces methane is tar bush Eremophila glabra at 10 to 20 per cent of intake.

Other bioactive substances prevent bloat and acidosis.

Many are also anthelmintic, meaning they reduce the worm burden by more than 50 per cent.

“When animals browse shrubs, they are not ingesting parasite larvae. In addition, when on a rotational grazing system, they regularly move into clean paddocks. That helps to break the parasite lifecycle,” Professor Vercoe said.

Jason Emms of the South Australian Research and Development Institute said sheep were not “lawnmowers”; they made decisions about what to eat based on what had previously been fed to them.

“Sheep learn quickly. They learn what to eat from their mum, their peers and by trial and error,” Dr Emms said.

Given a choice, sheep will eat a wide range of shrubs and grasses, perhaps as many as 20 different species, including small amounts from unpalatable shrubs.

Bruce Maynard, who farms in central New South Wales, has been growing saltbush as a forage shrub for 25 years and other varieties of shrubs for eight years.

“It is important to use shrubs the right way, providing sheep with a diversity of pasture,” he said.

“I’ve doubled my stocking rate because of shrubs and I don’t conserve any fodder now, which reduces my workload and machinery overheads.

“I’m able to choose the time to buy and sell stock. I’m buying when everyone else is selling.

“We’ve just had nine years of drought and there was always some feed from shrubs.

“Shrubs also provide shelter for lambing ewes and bring nutrients to the surface from deep in the subsoil.

“I call it my vertical real estate. We don’t use fertilisers any more.”

Mr Maynard has around 15 per cent of the area of each paddock planted to shrubs.

“We plant shrubs in alleys, preferably curved to improve the windbreak effect. Each alley has three rows, so all is not lost if we lose some shrubs,” he said.

The only block planting is in mini paddocks next to the yard, so we can leave sheep there overnight if necessary.”

Management is different with shrubs. Having enough water points is critical, as well as small paddocks, moving stock often and having shorter grazing cycles.

In addition, Mr Maynard only has a specific amount of land planted to shrubs, so the property would be attractive to croppers if he decided to sell up.

“We chose locally adapted shrubs established by direct seeding where possible,” he said. “They also help in fire suppression, act as a wind break, reduce evaporation and improve soil health.”

Dr Emms said a range of shrub species might work, but there was no short answer for each farm.

“Base your selection on shrubs that occur locally and are adapted to the environment, have been shown to be palatable by rangeland researchers, are woody perennials and are not known to have a potential as weeds,” he said.

The South Australian Research and Development Institute has investigated 119 different indigenous species of shrubs, plus a handful of exotics such as tagasaste and lucerne. These have been tested for palatability in the laboratory.

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