Shift in grazing management boosts capacity
Case study: Andrew and Scott Colvin
Location: Blackwood Creek, Tasmania
Property size: Nosswick — 950ha, Maitland — 160ha
Average annual rainfall: 750mm plus irrigation (nine pivot irrigators and 19 pivot circles)
Soils: Light duplex soils — poorly draining soils prone to waterlogging during winter
Enterprises: Mixed farming system — sheep (4000 Coopworth breeding ewes), irrigated and dryland pastures (white clover, annual ryegrass), cropping (annual ryegrass seed, poppies, beetroot, carrots, broccoli and processing peas)
After 35 years of set stocking, the Colvin family has made a radical change by moving to intensive rotational grazing, which has seen stocking rates increase by 20%, improved pasture utilisation and lifted weaner growth rates to levels of about 250–300gm/hd/day according to Scott Colvin.
Scott recently completed the Australian Wool Innovation (AWI)-funded Lifetime Ewe Management (LTEM) course, which highlighted the potential fit for rotational grazing in the Colvin’s mixed farming system.
“Our business is going through a transition phase this year in a number of ways,” Scott explained.
“And the way we manage our sheep and the pastures that underpin our prime lamb and wool enterprises reflects this.”
According to Scott, on his return to the farm during 2012 it was clear there were a couple of key challenges he and father Andrew needed to address to boost productivity and profitability in their purebred Coopworth operation: ewe-lamb condition leading up to joining, and weaner growth rates.
With a mid-September lambing, the traditional summer feed gap was central to both these challenges.
“We’ve always struggled for feed during late December through to the start of February,” Scott said.
“We wean before Christmas, haven’t got access to our ryegrass seed paddocks, or poppy ground and our peas are still under pivot — this all comes at a time when we are at our peak stocking rate.
After participating in an LTEM course and working closely with grazing expert Basil Doonan of Macquarie Franklin, Scott and Andrew have made some radical changes to their grazing management and the dividends are already becoming apparent.
“Essentially our problem was one of pasture utilisation,” Scott said. “In the past we have run our ewes in set-stocked mobs, which didn’t allow our pastures any time to recover from grazing, but this year we have changed our tack.
“With guidance from Basil we have invested in water and wire and shifted to an intensive rotational grazing system during the past few months.
“We are currently using a 30–60 day rotation, varying the stocking rate in line with pasture growth rates.
“We aim to start grazing the pasture at the emergence of the third leaf — the timimg of this will vary according to the season and seasonal conditions.
“Recovery time between grazing also will vary depending on the seasonal conditions and access to irrigation. The biggest thing is planning — you have to be aware of what is in front of you.
The Colvins started the ball rolling with the new approach at weaning.
“We condition scored our mature ewes at weaning and split them into two mobs —above and below condition score 3 (CS3),” Scott explained. “This year we aim to have everything at CS3 for joining during late April using better feed utilisation, without supplementary feeding.
“Our lighter ewes are running on the better quality feed and have been rotating through paddocks that have been locked up since weaning.”
Scott is managing his better-condition ewes for maintenance only.
“We also are ensuring our ewe lambs have access to high-quality feed and currently have 1500 ewe lambs working their way through a 40ha paddock of a mix of white clover varieties, with access to 10ha at a time.
“They move into each new section of the paddock when there is about 3000kg of dry matter (DM) and we move them on when there is about 1500kg DM/ha left, which equates to a feed utilisation rate of 1.5kgDM/hd/day for a 35kg lamb.”
Fast results Both Scott and Andrew have been impressed at just how quickly the benefits have started to flow from simple grazing management changes.
“Implementing rotational grazing after weaning has allowed us to increase our stocking rate over summer by 20%,” Scott said. “Last year we sold the bottom 15% of our mob in January because we didn’t have the feed to keep them — we now find ourselves with a feed surplus at a time of year when it is traditionally tight. We have recently bought 900 store lambs to use this excess feed.
Measure to manage
A key component of LTEM is to help producers gain skills in measuring and managing the condition of their ewes throughout the reproductive cycle and the amount of pasture dry matter produced by their pastures throughout the year.
“LTEM taught you to assess sheep and pasture (dry matter assessment) and to develop feed budgets, which then allows you to see if the ewes will go ahead under current conditions,” Scott said.
But for Scott the benefit has come from gaining a better understanding of how to influence pasture production through grazing management.
“Our recent experience has been about increasing feed production without adjusting any other input other than the number of animals in the paddock and the grazing period,” Scott said. Investing in pasture is expensive and by better managing what we have, we are getting more out of that investment.
“We are learning to better measure our pasture, understand the potential growth rates and production under current seasonal conditions, compared with long-term data and make decisions accordingly — if you don’t measure it you can’t manage it.
Planning within the known parameters allows you to improve future feed availability calculations and making more timely stocking rate decisions.
Timing of operations
By gaining a better understanding of the intricacies of matching pasture growth with livestock demand, and developing feed budgets throughout the year, Scott is evaluating and adjusting the timing of some of their sheep operations.
“We currently start lambing around mid September,” Scott said. “But there is scope to pull this back to the start of September, which will allows us to bring marking forward and better capitalise upon increased pasture growth rates and feed availability during spring.”
The Colvins are currently achieving marking percentages in the order of 150% in their mature age ewes and 100% in their ewe lambs and would like to improve on this.
“The system (bigger mobs) does put pressure on the livestock and certainly requires you to be more on the ball in terms of managing animal health.”
Andrew is philosophical about how far they can push marking percentages.
“We can do everything to optimise flock fertility — feed our rams on lupins leading up to joining, have ewes on a rising plane of nutrition, put lambing mobs in sheltered paddocks and manage parasites — but you can’t control the weather,” Andrew said.
While the large mob sizes are working well to maximize pasture utilisation at present, the Colvins will suspend rotational grazing across lambing, returning to mob sizes of 200. Post lamb marking mobs will be combined in order to the take advantage of spring feed under a rotational system again.
Contact: Scott Colvin
This story first appeared in the autumn 2015 edition of the Sheep Connect Tasmania newsletter
To read more about the theory behind Scott’s grazing management click here