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Mob grazing for dairy: can tall grass unlock underperforming fields?

Mob grazing for dairy: can tall grass unlock underperforming fields?

20 September 2022 Pasture resilience


The latest field lab sees six dairy farmers team up with researchers to investigate whether tall grass grazing practices can work for dairy herds - following successes in UK beef cattle. The idea is to test the practice on both milking cows and some young stock and dry cows to find out if mob grazing can add value to a dairy business.

The concept mimics the natural grazing behaviour of wild ruminants in big herds, which intensively graze in one area and then move on. The stock grazes on the basis that one-third of the forage is available to feed the cows, one third is trampled to feed the soil, and one third is left so the plant can regrow more rapidly. The cows are moved on frequently to prevent overgrazing.

Applying this method to grazing systems by controlling where cattle graze can allow the grass to grow up to 50 per cent taller meaning seed heads can develop and root structures are stronger, which boosts soil health and biodiversity.

The farmers testing mob grazing on dairy

Field lab participant Debbie Wilkins farms a 900-acre, mixed conventional farm on a floodplain in the Severn Vale with dairy beef and arable. She said: “I’ve heard mob grazing works well on brittle environments, which is not what we have here in the Severn Vale, so I am really keen to see how it works on my farm. After our first weighing, the tall stemmy grass is giving similar growth rates of 0.8 kg/day to the conventionally grazed grass, time will tell if there is enough nutrition to have good growth rates all season. There is a lot to discover and manage and it will be interesting to see how it progresses.”

Debbie is grazing weaned to 12-month-old calves in the trial, in two groups on daily moves. Half are on grass leys sown with grasses and herbs that cope with flooding, and the other half are on permanent pasture flood meadows. The tall-grass group is going in at high covers of 6000+ kg/dry matter (DM) on plate meter, and she reports that it is getting quite a bit of trampling which helps add organic matter to the soil.

Also involved in the trial are Tom and Sophie Gregory, who have been battling with underperforming fields on their 900-acre, organic dairy farm in Dorset. They farm a block calving system of 360 cows and are determined to utilise all their fields while minimising their use of organic fertilisers and supporting better biodiversity and water quality, but without risking the yield of their herd.

Tom thinks there could also be animal health benefits. He said: “As the animals will move on at a faster rate there will potentially be less flies, the stock won’t be grazing as low meaning there should be less exposure to fluke and worm eggs. And we should minimise the risk of underfeeding as they will be eating what they need – resulting in optimum health and production.”

The impact of tall grass grazing

While there is a need to maintain animal health and production, the trial also aims to test and research improvements in soil health, particularly improving the balance of bacteria and fungi to increase nutrient availability in fields.

Underpinning the trial are periodic soil samples, the farmers’ ongoing pasture assessments, and periodic forage samples – with research support from Harper Adams University.

In addition, one farm is working with Folye Food Group to look at growth rates of cattle, weekly calf worm counts, dung beetles and brix measurements on same group as this trial. They aim to see if paddock-style grazing reduces need for wormers and if the diverse herbal seed mix is better than typical grass-clover pasture.

Sarah Morgan from Harper Adams University, who is supporting the trial, said: “Biology takes quite a long time to adapt to management changes. Although this field lab is set to run for three years, that time span may yet prove to be too short to find significant changes and differences between the tall grass and control treatment. I’m hoping to see that tall grass can be used as a tool by dairy farmers to improve soil health and functionality. It will be really interesting to see how similar the results will be compared to the Agri-Tech Cornwall funded ‘Cell grazing’ project and other previous studies, and I’m excited to learn more about how grazing management effects soil bacteria and fungi in particular.”

Making mob grazing work for dairy

One hope is that tall grass grazing is not just considered for sheep or beef – where the nutrient demand may be lower – but that there is scope to embrace this style of grazing and its holistic approach for dairy herds too, unlocking the full pasture growth potential on all available land. This may not be with the milking herd but could still be achieved using dry cows or young stock, where nutritional demand is lower.

Rebecca Swinn, Innovative Farmers manager said: “Field labs are a great way to test on-farm ideas. They provide a framework of research support and technical data which can be a stumbling block preventing farmers from testing their own theories. Bringing farmers together means the benefits also stretch far beyond just one farm. Tall-grass grazing is a practice utilised by beef and sheep farmers but less so in the dairy sector, due to the need for a consistent supply of high-quality forage in the diet. This field lab will test the premise that you can successfully integrate tall-grass grazing into dairy farming as a means of improving the soil health of poorer fields.”

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