The subject attracted about 100 farmers to Farmwise consultant Brent Boyce's annual field day near Nelson, with many already convinced that mowing is lifting milk production.
Figures for Evan and Adrienne Baigent's Kohatu farm, where the field day was held, show an 11% increase in megajoules of metabolisable energy (MJME) since they began mowing pasture, taking it to 22.4 million MJME utilised, with no other variation in inputs or management to attribute the increase, Boyce told the field day. This season they are targeting an extra 4.1% lift in MJME.
He attributed the increased gain to a combination of increased pasture quality, more grass grown, higher intake, and more energy because reduced grazing time means more resting.
Production for the 128ha mostly irrigated dairy farm, which milks 415 cows at the peak of the season, increased from 157,092kg milksolids (MS) and 1224kg MS/ha to 175,680kg MS and 1368kg MS/ha. This season they estimate total production of 185,000kg MS and 1441kg MS/ha.
"I'm seeing a lot of farms achieving production and profitability results that I wouldn't have expected before they adopted strategic mowing. These farmers are producing 150 to 200kg MS more per hectare with no increase in inputs. Guys who were producing 1400-1500kg MS/ha are now getting 1600kg."
His advice to farmers was to mow in front of the cows when there was a surplus of feed to increase cow intake, and behind the cows to improve pasture quality when there were clumps left behind.
"Those clumps are your worst enemy. They'll still be there three rounds later."
Normal grazing residuals were 1500kg DM/ha, Boyce said, whereas clumps were more likely to be at 2400kg DM/ha. Those clumps grew twice as fast as the rest of the pasture and could cover 10% of the paddock.
"We need those clumps back in the round and in a harvestable grazing state for the cows."
To mow paddocks in front, Boyce said ideally there should be at least 200kg DM/ha more than the cows' requirements. By doing this, the farmer was able to take out small surpluses and maintain a suitable grazing rotation that best matched third-leaf emergence.
Peer-reviewed literature on mowing was based on data that assumed mowing either took residuals down to about 1300kg DM, or mowed at the same height as cow grazing, Boyce said, whereas he was suggesting mowing residuals between 1550kg and 1600kg. Information to date ignored the increased ME levels from mowing and he would like to see research carried out to evaluate the value of today's strategic mowing techniques.
"Because we're mowing at 1550 to 1600, we've got a faster growing point. Normal cow grazing to a 1500 residual typically gives 90% of the residual at 1400 and 10% at 2400 with the clumps."
The Baigents farm had settled at about 159,000kg MS operating on a system three that equated to 10-20% of feed imported and for years it had been run by sole managers. They wanted to maintain cow numbers to suit the 30-aside herringbone dairy, increase pasture available per cow and increase the per cow production and profitability using the same inputs. To take the farm to that next level needed drive and enthusiasm and that came in the form of 50:50 sharemilkers Brian and Hannah Dineen.
‘It's not just the quality, but conception come mating time. We're fully feeding those cows right up to mating.’
The Irish and Kiwi team had some experience with mowing in Canterbury and considered it a practical solution for grass quality and intake at Kohatu. Last year they mowed 250ha, which included some paddocks being mown four to five times while others were mown only once or twice. This year they anticipate mowing 350ha.
"One of our hardest tasks is controlling our residuals, but each time I'm going in with the mower I'm guaranteeing those residuals," Brian said. "Those clumps are going to produce stalky feed and so it's a domino effect that becomes worse and worse."
When mowing before grazing, the Irishman mows just 45 minutes to an hour before the cows go into the paddock so the grass is only just starting to wilt and is still palatable.
"And when we put them in, it's a great sight to see those girls hoover it up and put it in the vat."
He began mowing in late August when grass growth took off and considered it was never too early to start. The mowing had the added benefit of suppressing thistles, while mowing on other farms around the region was helping to control docks, pakihi rush, and giant buttercup.
Even with the cost of mowing, farm working expenses on Baigent's farm dropped by 46 cents a kg MS because costs were spread over higher production. It puts service costs for the tractor at $3 an hour, fuel costs $21 an hour, running costs at $24 an hour, and blades at $4.57 each. General consensus was that mowing, including depreciation, cost about $50/ha.
With a lower payout looming, Boyce looked at the financial implications of mowing. Last season the farm produced an extra 18,588kg MS which resulted in a net margin of $101,000 including the cost of mowing. Working on $5.30/kg MS at the time of the field day, Boyce said the extra cost of mowing would yield an additional $26,000 compared with 2013-14 if it reached its targets and that would give a net margin of $127,000 compared with 2012-13 when there was no mowing.
Pre-mowing at the field day.
The farm could drop 200 tonnes of palm kernel and mow just 130ha of pasture which would make a saving of around $66,000. But total production would fall to about 130,700kg MS because of less feed and pasture quality and that would reduce the net margin by $73,896 compared with the 2012-13 season.
Alternatively, they could mow 350ha but drop the palm kernel, which would reduce production to about 157,760kg MS, similar to the 2012-13 season. That would increase profitability by $51,350 compared with that same season, but significantly lower than if palm kernel was also retained.
Practical advice for mowing was also thrown in to the field day, such as the importance of keeping blades sharp to avoid frayed tips on the grass that would inhibit growth.
On the fertiliser for the mowing, between 25 and 30kg/ha of nitrogen was usually incorporated in the mix with potassium and sulphur applied behind the mower if budgeted. On the irrigated areas the nitrogen was applied at any time of the day, while the dryland paddocks were given nitrogen applications in the evening to catch the dew.
The farm has 15ha of dryland and those paddocks were usually mown after the cows had grazed them to improve grass quality as Boyce said there was no point mowing in front of the cows if the pasture was "rubbish".
"Let the cows get into it and then mow it afterward."
He recommended pre-mowing no more than 50% of non-irrigated grazing on any day and preferably ahead of the night feed. Mowing too much area in one round or when growth was below demand resulted in reduced cover and growth rates through dry periods.
Paddocks of new grass on the Baigent farm had been mown three times to improve the quality as young stock that could have done the job were not grazed on the farm.
Boyce said a major advantage of mowing was that it gave the business the ability to control increased variability in feed spikes rather than wait for a contractor.
Murchison variable-order sharemilker Jason Macbeth was another advocate of mowing and he told the field day he averaged three mowings a paddock last year, adding up to 273ha, and this would be his fourth season.
‘I'm seeing a lot of farms achieving production and profitability results that I wouldn't have expected before they adopted strategic mowing.’
He began with topping grass after the cows but decided too much grass was going to waste, so began mowing before the cows so they would eat more as they came up to mating.
"It's not just the quality, but conception come mating time. We're fully feeding those cows right up to mating."
This spring he had so much grass that he was sending the cows back to the same paddock, where they were happy to clean up the mown grass for a couple of hours before moving to the next paddock.
Boyce said many of those at the field day had been following the results achieved at Lincoln University Dairy Farm and were adapting those practices to their own farms.
The three rules of strategic mowing
1. Top any clumps or high residuals left after grazing.
2. Mow excess feed in front.
3. Always let the cows graze it first when you have it right.
