Cell grazing: lessons learned in trials across the NT over the last 15 years
By Robyn Cowley, Dionne Walsh and Jane Douglas, NT Department of Primary Industry and Resources
Proponents of intensive rotational grazing or ‘cell’ grazing suggest it will increase the productivity and profitability of northern cattle businesses. It seems like a good idea to regularly rest pastures, to help them recover from grazing, and we know from studies in northern Australia that wet season spelling is beneficial. So what about rotational grazing? Here we summarise the impacts of rotational grazing compared to continuously grazed paddocks when trialled in four locations in the NT.
|Trial||Beetaloo||Newcastle Waters||Pigeon Hole||Douglas Daly Research Farm|
|Median rainfall (mm)||450||476||650||1209|
|Trial duration (years)||4||3||3||6|
|Paddock size (km²)||2-25||1-8||1.2||0.06|
|Stock density when grazed (AE/km²)||846||370||404||2773|
|Graze period (days)||2-5, some open gates||15 (1-116)||5||1-3|
Rotationally grazed pastures did not stay in phase two growth during the dry season. They stop growing and become dormant when there is no more soil water for them to regrow after grazing. While cell grazing may work in regions where there are multiple growth events throughout the year, this is not the case in northern Australia and this is what sets north Australia apart from other areas where rotational grazing is regularly practiced (e.g. irrigated dairying country, New England Highlands).
In the three to six years of the trials, rotational grazing did not affect pasture yield, composition or soil carbon, either for better or worse, compared to continuously grazed paddocks.
Carrying capacity of rotationally grazed paddocks was the same as fully watered (within three kilometres of water) continuously grazed paddocks.
Diet quality (crude protein) and live-weight gain is sometimes lower in rotationally grazed, possibly because cattle are forced to eat less palatable pastures, which reduces intake.
The higher operating costs (1.5 to 1.8 times higher) and higher capital investment of rotationally grazed systems led to poorer economic performance compared to continuously grazed systems.
But there were some benefits of rotational grazing. Smaller paddock size of rotationally grazed paddocks was associated with more even grazing with distance from water. Managers observed better temperament of their cattle, and had sale cattle on hand without needing to muster large paddocks. Importantly rotational grazing provides an opportunity for wet season spelling, which improves pasture condition, even in otherwise continuously grazed systems.
Fully watered continuously grazed paddocks with appropriate stocking rates perform as well as or better than rotationally grazed systems. But wet season spelling is still a good idea to keep your pastures healthy.
The lower or similar production combined with higher operating and capital costs of rotationally grazed make them less profitable at least in the short term. Unless rotational grazing leads to higher carrying capacity, there is no potential for it to lead to higher profit given the higher costs.
Getting the scale of development right makes a big difference to economic return on investment. At Pigeon Hole the minimum paddock size to maximize economic returns was between 20–30 km². Smaller paddocks did not pay their way.
Neat conversion trick between cell grazing and set stocking units
Cell grazers and set stockers tend to talk a different language, and it can be hard to decipher what the other mob is talking about.
What does it mean when a cell grazer tells you that a paddock has 40 SDH worth of feed in it?
If a set stocker tells you they reckon their paddock can safely run 7 AE per km² what does that convert to in SDH?
SDH – Stock days per hectare. The number of 450 kg dry beasts that can be run for one day on one hectare to utilise 50% of the preferred pasture plants.
AE/km² - Animal Equivalents per square kilometre. The number of 450 kg dry beasts that can be safely run all year (365 days) in 1 km² to utilise 50% of preferred pasture plants.
To convert between the two systems we are converting between 1 day to 365 days (x by 365) and from 1 ha to 1 km² (÷ by 100). So the conversion factor is 365 ÷ 100 = 3.65.
To convert from SDH to AE/km², divide by 3.65.
To convert from AE/km² to SDH, multiply by 3.65.
Some examples are:
40 SDH = 40 ÷ 3.65 = 11 AE/km².
7 AE/km² = 7 x 3.65 = 25.5 SDH.
Last updated: 28 September 2020
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