Often under-valued or even ignored, brassicas can have a role in bridging summer grazing gaps, boosting autumn production or providing the mainstay of out-wintering systems. They can be a high energy feeding option and a vital break crop in grassland reseeding.

In this bulletin, we review the potential of a range of crops, including kale, forage rape, modern hybrids and high energy root crops such as swedes. We consider the impact of today’s agrochemical restrictions and offer some fresh thinking on utilisation.

Whilst quality grass and clover leys will remain the cornerstone of forage-based livestock businesses in the UK, brassica fodder crops offer a range of complementary solutions that can significantly enhance homegrown resources.

Building business resilience with brassicas

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Choose kale for quality firstKale-based out-wintering of cattle has gained popularity as producers seek lower-cost and more sustainable systems, but success requires a variety fit for purpose. According to William Fleming of Germinal GB, growing the wrong type of kale could result in half the crop being left in the field, which would be potentially disastrous as the feed budget should be based on the cattle utilising 80-90%.“There is a lot of research showing that kales with a superior leaf-to-stem ratio and more digestible stems deliver better animal performance,” William Fleming points out. “This trait is far more important than total dry matter yield. Cattle achieve as much as a 62% increase in daily liveweight gain when grazing leafy kale varieties with highly digestible stems.”These established research findings have been confirmed by observational trials throughout the UK. Different kale varieties were put in front of cattle with startling results – in some cases, only the leaf canopy was grazed with the stems being completely overlooked by the stock.“The aim is to be left with a brown field for your follow-on crop in the spring and this means sowing a crop that will be fully utilised by the cattle,” continues William Fleming. “The objective is to leave minimal residual green matter in the spring. “Maris Kestrel is the proven fodder kale variety and the one most farmers come back to time after time. Nothing beats it because it stands up well – yet both its leaves and stems are highly digestible.”

Year round feeding costs can be cut dramatically by adopting a multi-graze management strategy with selected fodder crops, says Helen Mathieu.With the appropriate management, a number of grazing brassicas offer second and often third grazing opportunities, allowing establishment costs to be spread across significantly increased dry matter tonnages.

Multi-graze fodder crops currently available include the grazing turnip variety Appin and the hybrid brassicas Swift and Redstart.

“Forage brassicas have traditionally been seen as a single grazing crop in the UK, but our experience in other parts of the world with some of the newer varieties shows that a multi-grazing strategy is perfectly possible,” says Helen.

“The key management point is to leave a good 10cm of stem, with plenty of nodes from which new growth will develop. This is best achieved by dividing the field into four and grazing each block for five to seven days – possibly less depending on growth rates - and then starting back in block one. If strip grazing with cattle it may be advisable to use a back fence to protect the regrowth.

“In hungry soils, where the first blocks have been grazed by the end of July, there is an option to top dress with nitrogen.

“Assuming your original crop has provided in the region of 3 - 4,000kgDM/ha of available fodder, you can expect around 75% (2,500kgDM/ha) from a second grazing, and then as much as 60% (2,000kgDM/ha) from a third grazing in some cases.

“Bearing in mind that the only additional cost is the fertiliser, your overall cost/kg DM is going to be cut by a minimum of 40 - 50% by adopting a multi-graze strategy.”

Helen Mathieu says that multi-grazing can be used with all classes of ruminant livestock, including dairy cows, but is a particularly effective method of fattening lambs. Best results will be achieved for crops sown in fertile soils by early June.

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Multiple grazing halves cost per tonne

Minimal amounts of plant residue from grazed Maris Kestrel kale indicate high levels of utilisation by livestock.

Giving brassicas the best start“Valuable forage crops such as kale, swedes and hybrid brassicas will need to be grown with additional care and greater attention to detail following the withdrawal of neonicotinoid seed treatments,” says Germinal’s Felicity Lenyk.

She recommends a five-point plan to ensure crops come through the critical early weeks of establishment with sufficient vigour to withstand any pest threat.

1. Prepare a fine and firm seedbed; avoid clods and plant residues to ensure good seed-to-soil contact

2. Achieve optimum soil nutrition; carry out soil analysis in good time and apply fertiliser to correct P and K levels where necessary. Aim for a pH close to 6.5

3. Choose varieties with good early vigour and disease resistance

4. Avoid sowing at the same time as large scale brassica crops nearby (e.g. oilseed rape). These act as a reservoir for pests

5. Maintain a rigorous rotational policy; in the case of brassicas avoid growing more than one year in six at a given location.

Recognising the key role that brassicas play in boosting production from forage, Germinal are investing significantly in sourcing and developing new varieties and systems. This includes product development abroad and in the UK, and a programme of trials at its new Research Station in Wiltshire.

For mid-Wales upland sheep farmer Rob Powell, several different root crops combine to make a significant contribution to his 2,300-ewe enterprise, but swedes – providing the basis of ewes’ rations from late December through to lambing – are the most valued.He currently grows 18 acres of Triumph swede, which he aims to direct drill into a burnt-off sward by mid-June, having established a similar acreage of fodder beet in May and with around 10 acres of stubble turnips to go in before the end of July.

“It suits us to stagger the establishment of the root crops, so we can work it around workloads and grass availability,” he says. “We apply chicken muck or compound fertiliser to ensure the P & K levels are right, and for swedes we want a pH no lower than 5.8.

“For swedes we tend to pick a dry field – it’ll stand drought better than wet. We like Triumph because it gets away well and reaches canopy closure quickly. We’ll spread some slug pellets as we drill and usually apply 50kgN/acre at third leaf stage. It’s important to keep an eye on the slug populations and apply some more around the field edges if necessary.”

Rob aims to have sheep on the swedes from Christmas and works on the basis of 10 acres feeding 500 ewes for three to three and a half months.

“We usually block graze on a weekly rotation and find the utilisation is really good,” he adds. “All the ewes have a mineral bolus, which includes iodine as swedes are low in this trace element, but otherwise its just a case of providing a run-back area and a good water supply.

“I find the ewes prefer swedes to the other root crops and tend to do better on them. It’s a simple and relatively low-cost system that works for us.”

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“We usually block graze on a weekly rotation and find the utilisation is really good ...”

Swedes the favoured root for ewes

Withdrawal of agrochemicals used widely to control common pests of new grass reseeds should not hamper livestock farmers’ ability to renew swards, as the threat can be minimised through effective cultivations and/or the strategic use of break crops.So says Bill Reilly of Germinal GB in response to the banning of chemicals such as chlorpyrifos-ethyl products (e.g. Dursban).

“These agrochemicals have been used effectively for many years to control pests of new grassland such as leatherjackets and frit fly, but they are being withdrawn,” Bill Reilly explains.

“These pests can devastate new leys if not controlled, but the risks can be avoided through effective cultivations and the use of brassica break crops. The use of fast-establishing hybrid brassicas or kale have the added benefits of providing an additional source of high quality grazing, reducing the effect of any forage shortfalls between leys. This can be timed to provide late summer, autumn or even winter grazing for cattle or sheep.”

Leatherjackets result from the crane fly laying its eggs in late summer, with these then developing into larvae over the winter months. These larvae (leatherjackets) feed on the roots and stems of plants just below the surface and cause crop damage (loss of yield and large bare patches) from early spring until mid-summer when they pupate.

The frit fly frequently produces three generations a year, with the larvae of the third generation emerging in late summer. These larvae can cause a great deal of damage to grass leys and cereals when they tunnel into the centre of the plant causing dead-hearts before then moving to another tiller or plant.

“Ploughing and cultivating in summer, and sowing a break crop, will disrupt the life cycle of the crane fly and is known to reduce leatherjacket populations by 50%,” adds Bill Reilly. “In a similar way, the risk of frit fly damage can be minimised with the use of break crops, particularly when the period between planting and utilisation is at least two months.”

In addition to their effectiveness as break crops, brassicas will also boost short term feed availability.

If drilling in mid to late summer Bill Reilly recommends the fast-growing hybrid brassicas Swift or Redstart, which have the potential to provide up to 10 tonnes of dry matter per hectare within 10-12 weeks of sowing.

“By growing brassicas in between old grassland and a new reseed you are cleaning the ground very effectively, as there are two opportunities for weed control,” he says. “In some cases, there may still be time to do this ahead of an autumn reseed, using the brassica as a short-term grazing crop to fill a late summer forage gap. Alternatively, the brassica could provide autumn or out-wintering forage, ahead of spring reseeding.”

Brassica break adds value to grassland reseeding

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“By growing brassicas in between old grassland and a new reseed you are cleaning the ground very effectively...”