Rotational grassland grazing management
Rotational grazing can boost livestock yields by as much as 20% when grass is used correctly, according to grassmaster Charlie Morgan.
Managing and measuring grass growth is crucial for optimal production through rotational grazing, said Mr Morgan at the recent National Soil Symposium in Bristol. “Grass is too valuable a resource not to measure,” he said.
One Sussex sheep farmer and client of Mr Morgan who benefited from switching to rotational grazing has recorded improvements in daily liveweight gain of up to 180g a day.
The previously set-stocked triple-worm-resistant sheep were struggling at weaning and losing weight instead of gaining. After changing to rotational grazing, more finished well with their mothers and were sold before weaning, improving the bottom line.
“The combination of addressing soil nutrients, reseeding a high quality grass and clover mix and making sure it is used to its full potential has given the farmer the best opportunity to get the most from his animals,” explained Mr Morgan.“ Even though they are worm challenged, we were able to improve the system after the improvement in feed quality.
Planning a system
Farmers considering adopting a rotational grazing system need to plan their paddock sizes and stocking density carefully, based on how many kilos of dry matter are available a hectare. This can be calculated by taking a current sward height measurement and subtracting the residual sward height measurement (the height at which the livestock must leave the field).
How much each animal will eat plus a 20% wastage figure can then be used to work out how many animals can be on the pasture and for how long. The size of each paddock may also be affected by farm labour availability and handling systems.
“The Sussex farm system geared the paddocks to have 650 lambs in one batch. They spent 3-4 days in a 3ha paddock and moved around eight different paddocks in a 24-day cycle,” said Mr Morgan.
Another benefit of well-managed rotational grazing is grass is always left with enough leaf surface area to regrow once the animals leave the paddock, shortening the length of time between use.
Mr Morgan advised entering a paddock at about 2,700kg/DM a hectare and leaving at between 1,500-1,750kg/DM a hectare, depending on how well the animals graze. When set-stocking, grass in certain areas can be grazed too short. With no leaf, there is little opportunity for sunlight capture, which is needed to make food for the grass to regrow, negatively impacting on productivity.
“The most critical thing is when to leave the fields. Residual sward heights are governed by the way the animal grazes; cows wrap a tongue and rip where sheep nibble down tight. The leaving point for cattle should be a sward height of 6-8cm and 4-6cm for sheep, (shorter in spring, longer in autumn), any lower than these points and the animals are not getting enough intake for the energy expended during grazing,” said Mr Morgan.
Measuring sward height
There is a wealth of tools available for sward height measurement and increasing technology is not without the heavy price tag. The message from Mr Morgan is to measure in any way you can.
“A mark on the wellie boot is the simplest option, but sheep farmers can use sward sticks for more accuracy as they are grazed tighter, and plate meters are good for cattle. How often you measure depends on the time of year; from weekly between May and June, to once every three weeks this time of year,” he added.
Reseeding
Reseeding is expensive, so Mr Morgan’s advice is to be aware of what you’ve got and look after it. It is vital to keep pastures in good condition; “test soils and measure swards, feed them and make sure the vast majority of grass is taken by the animal, he said”
“Mowing is a better way to control uneven grazing and increasing weed species than being smashed with a topper. Topped grass is whipped, damaged and lets in disease. Once the animals go back in, it only takes 12 hours to mop it all up and you can start again at a clean growing point.”
Rotational grass seed varieties
| Variety | Benefits |
| Intermediate and late heading diploid rye grass | More persistent, better seasonal growth patterns in spring and autumn, improved protein |
| Small to medium leaved clover | Small-leaves close to the ground suit tighter sheep systems |
| Timothy grass | Better in the spring, earlier growing, more resilient to our climate |
Academy: Managing grazed grass