An independently managed pasture trial that has already highlighted benefits in prime lamb meat production from grazing different perennial ryegrass cultivars is this year turning its attention to measuring the impact on Merino wool production.

The research aims to build on results originally captured for the Pasture Trial Network (PTN) variety selection tool, which compares the performance of more than 100 varieties across key pasture species for the red meat industry in southern Australia.

Developed by Meat and Livestock Australia in partnership with major pasture seed companies, the online tool enables in-store agronomists, farm advisers and producers to select varieties with the greatest chance of success, based on seasonal dry matter production in plot trials carried out in a range of environments. Persistence after three years was also measured.

The varieties covered by the selection tool include Victorian perennial ryegrass, a long-standing favourite found in paddocks across higher rainfall zones, and relative newcomer, Base AR37, a late-heading perennial ryegrass bred in Australia by PGG Wrightson Seeds.

Independent agricultural advisory business Meridian Agriculture was approached by Wrightson (now DLF Seeds) in 2016 and engaged to put the two ryegrass varieties through their paces under intensive grazing pressure in a commercial prime lamb production enterprise. This led to a demonstration trial being established on Tony Fleetwood’s property at North Byaduk in western Victoria.

“The PTN tool is extremely useful for retail agronomists putting together recommendations for their clients, but Wrightson wanted us to take it a step further and test these two options in a real-life situation, and then measure animal performance,” says Meridian senior agronomist Andrew Speirs.

“We chose Tony’s farm because he was pushing the production envelop with his maternal composite ewes, utilising every bit of pasture to get maximum results. Some ryegrass cultivars don’t persist under a relatively heavy stocking rate, so we thought it would be a real test.”

The trial was set up in a 15-hectare paddock with consistent clay loam soils. The paddock was divided into two equal sections. Victorian ryegrass was sown in one half at a rate of 12kg per hectare, with 5kgs each of Leura and Campeda sub clovers; Base was sown in the other half at the same rate, with the same sub clovers.

Throughout the trial, the paddocks were rotationally grazed up until about six weeks prior to lambing in mid-August. They were then set stocked according to their capacity through to at least marking, about six weeks after lambing.

“Our aim was to measure how much lamb we could turn off per hectare by early summer. If we needed to put more sheep in to utilise the pasture we did, or if the ewes started losing condition, we took some off,” Mr Speirs said.

Having seen Base in other trials, Mr Speirs was expecting it to perform better than Victorian, but he and Mr Fleetwood were both surprised at the extent of the difference, and what they discovered about the newer variety’s growing habits, persistence and livestock grazing preferences.

By 2021, Base had produced average returns of $606 more per hectare per year, calculated on kilogram liveweight production. Ewes kept on Base also had improved body condition scores.

Even in dry conditions in 2019, Mr Speirs said Base out-persisted Victorian, defying common perceptions that Victorian handles low rainfall better than modern cultivars. By 2020, Victorian ryegrass plant numbers had reduced significantly, measuring 65.3% compared with 81.3% for Base.

“The Victorian ryegrass persisted almost as well in the first two years, but that’s because the stock basically refused to eat it from about late September, so it ran to seed. Once it starts to go reproductive the sheep won’t touch it, so even though the pasture lost plants, seedling recruitment held it together.

“Base is very different. It might have gone to head once in the five-year trial, because the sheep kept eating it throughout the spring, so it stayed vegetative much longer. It was so palatable they absolutely flogged it, but they didn’t manage to kill it. The plants we sowed persisted and recovered more quickly than Vic coming out of summer.

“This was really apparent by autumn 2018. By May the section sown to Base already had 1500– 2000kg of feed on offer. Then we tested it for metabolisable energy and protein and calculated the number of grazing days. It had almost twice the carrying capacity for autumn than Victorian, which meant the pasture was well set up to carry stock into winter.”

Mr Speirs said put some of Base’s persistence down to a surprising characteristic he discovered when he dug up clumps. “If Base is well grazed it actually produces tillers underground, which is something no-one had really noticed before. It’s very unusual for a ryegrass to do that.”

He said that while Base performed well, it was important agronomists and farm advisers recognised it wasn’t suited to every producer, because it required managing in a particular way. “When Base runs up, it sends tillers out aerially, not on the ground, so you can lose plants by being too kind to it. You need to graze it hard in the spring and early summer if you want persistence.

“But the most important message is that you should focus more on the productivity outcome when you are recommending seed, and not the price. Base is more expensive than Victorian, but for an initial outlay of $72 per hectare, we made $600 more per hectare for five years in a row calculated on modest liveweight prices. That’s $3000!”

With the original trial wrapped up, a new trial is being conducted by Meridian on a property at Cavendish to assess meat and wool production in 1.5-year-old Merino wethers.

In the five months from October 2022, Base produced 62.5kgs more in red meat per hectare and the sheep were 0.2 better in condition score. “And when we measured faecal egg count, the wethers on Base didn’t require drenching, while the other mobs did, which is likely a result of them being in better condition, so better able to resist worm infestations,” Mr Speirs said.

The next step is to measure wool production. Fleeces from the wethers were weighed and micron tested during the 2022 shearing, with the first lot of comparative data due to be collected in August.