Brassica fodder crops have grown in popularity over the last decade, providing an alternative and highly cost effective source of homegrown feed within the widespread drive to increase milk production from forage.
New varieties and fresh ideas around management have certainly helped maintain the momentum, with this best demonstrated by the modern hybrid brassicas.
According to forage specialists Germinal, sales of the kale/rape hybrids Redstart and Swift reached unprecedented levels in the past 12 months, with applications in the dairy sector ranging from summer catch crops to out-wintering.
“Versatility is certainly a key factor with the hybrid brassicas,” says the company’s national agricultural sales manager Ben Wixey. “We are seeing their value in dairying systems in a wide range of situations, from supplementary grazing for milking cows through to the mainstay of an over winter ration for dry cows or youngstock.
“To make the most of these crops, however, it’s important to understand the nutritional value of what you have and to manage the system for optimum utilisation. From the work we’re doing, out in the field and at the Germinal Research Station in Wiltshire, we know hybrid brassicas have the potential to grow up to 10 tonnes of dry matter per hectare, with feed quality as high as 30% protein and 13MJ/kg ME. With this kind of feed value, it’s important to make full use of the crop, with 80-90% utilisation possible through good grazing management.”
One area where Germinal has been focusing attention, in order to maximise the return on investment, is multiple grazing. The hybrid brassicas Redstart and Swift have the potential to regenerate after grazing, with aftermaths offering additional dry matter production from second or even third grazings. In addition to the extra feed generated, multiple grazing will increase the break crop benefits and lead to higher soil fertility for following crops.
Germinal included multiple grazing in its 2018/19 farm trials programme, to investigate the value of this practice and establish some key management principles.
Whilst many aspects of the management are consistent with those that apply with single grazed crops, several points specific to multiple grazing emerged.
“To have the potential for multiple grazing crops ideally need to be drilled no later than early June,” explains Ben Wixey. “It’s then important to manage the first grazing in blocks, as opposed to strip grazing, as this will minimise the amount of damage done to the crop.
“Unlike with a single graze crop, where you are looking to maximise the utilisation throughout, when seeking to multi-graze it’s better to move stock on when stems still remain. This will accelerate the rate of regeneration and mean regrowth is available for grazing within six to eight weeks.
“If the second grazing is the final grazing, then manage for maximum utilisation, but if a third grazing is the target then aim to minimise damage and leave the stems to accelerate regrowth.”
Whether growing brassicas for a single grazing or for multiple grazing, factors such as nutritional quality, palatability and crop utilisation remain important. As with any other part of the ration, the attitude should be to know what you are feeding and to maximise intakes.
“Utilisation is an essential part of the picture,” adds Ben Wixey, “because crop left on the field after the stock has gone is a lost opportunity and wastage that businesses should seek to avoid.
“Good grazing management is certainly integral to the success of any system, but it is also important to consider the quality of the forage presented to the stock.”
Leaf versus stem
In crops such as hybrid brassicas, the leaf to stem ratio is a key factor in crop quality and subsequent livestock performance. It is a factor that will vary, but there has been little research to date to establish individual variety characteristics.
Note: When the intention is to multiple graze, stock should be moved on when the leaf has been eaten but stems remain, as shown. Management for higher utilisation should be used for the final grazing.
“We’ve carried out field trials on some of the main hybrid brassicas currently grown, measuring the relative dry matter of leaf and stem at different stages of the season and also recording the nutritional quality in the different components,” explains Ben Wixey.
“Total production potential is important, but the relative value of leaf and stem is arguably a more important level of detail, as is an assessment of what stock will actually eat.
“Unsurprisingly, the stem is of lower feed value than the leaf in all cases, but that does not mean the stem should be considered a waste product. We’ve found marked variation in stem quality between varieties and – in the case of Redstart in particular – the higher stem quality can be directly correlated with the extent of crop utilisation.”
Overall qualitative results from Germinal’s field trials show what a good nutritional balance is provided by the hybrid brassicas, underlining their real value and again emphasising the importance of utilisation.
Note: Variations in utilisation are clearly visible between Redstart hybrid brassica (left) and another leading variety. Drilling date and sowing rate were identical, but greater crop rejection on the right amounted to 2.8tDM/ha.
Brassica forage crops are included in the programme of trials currently on-going at the Germinal Research Station, now established near Melksham. Replicated trials now in the ground are looking at companion cropping and different cultural establishment techniques to limit damage from flea beetle. Further work is also being done on leaf and stem ratios, and the relative contribution each component makes to yield and nutritional quality.
Successful establishment of hybrid brassicas
Table: Yield and quality of hybrid brassicas (Redstart, multiple grazing)
DM (t/ha) **
DM content (%)
First grazing (leaf)
|4.0 - 6.0||12-14||12-13||20-24|
*Nutritional value of stems sampled in late February was 11.6MJ/kg ME and 17% crude protein, showing a higher than expected quality.
**Overall cost of production at multi-graze location was calculated at 3p/kg of dry matter
Source: Germinal field trials 2018/19