Winter brassicas provide both cost-efficient and high-quality feed for livestock. Outwintering on brassicas mitigates the need for winter housing and bought-in concentrates, helping to cut costs. From Maris Kestrel kale and the hybrid brassica, Redstart, through to Triumph swedes and Appin turnips, brassicas offer high-quality grazing to suit a range of needs during the winter months.
Grazing brassicas such as Maris Kestrel, Redstart and Stego usually begins in late October or November, running through until February. This autumn’s mild conditions are likely to mean little pressure on forage, with grazing continuing as normal until target covers and residuals are met.
For those beginning to graze brassicas, here are some important points to remember:
Calculating crop yield
Understanding the dry matter yield of brassica crops is vital for reliable feed planning and successful grazing. Having an accurate figure for yield helps calculate daily grazing requirements.
Take a number of representative samples from each field:
- Within a 1m2 area use garden shears to cut each plant to around 10-15cm from the ground
- Weigh the cut crop in a bag to give the fresh weight per m2
- Multiply the fresh weight by 10,000
- Multiply this figure by the expected dry matter percentage to give dry matter yield per hectare
Expected dry matter percentage for commonly grazed brassicas:
|Crop||Dry matter (%)|
|Kale (eg. Maris Kestrel)||12-15%|
|Hybrid Brassica (eg. Redstart)||12-14%|
|Turnip (eg. Appin)||9-12%|
|Swede (eg. Triumph, Marian)||10-12%|
If you know you need to carry livestock on the brassica for a certain length of time, divide the length of the field by the number of days required. For example, if a field is 200m long and needs to last three months (90 days), the daily grazing strip needs to be 2.2m (200/90). It is still important to calculate the DM yield, however, as the daily allocation may not be sufficient to adequately feed the stock and additional supplements will be required.
Brassicas provide a nutritious, high-energy feed but are naturally low in fibre so an additional fibre source, such as silage, hay or straw, is needed. Brassicas should form no more than 70% of the diet’s dry matter content, with the additional fibre source meeting the remaining 30% of their daily dry matter requirement.
Brassicas are also low in minerals such as selenium, iodine, copper and cobalt. Give a mineral bolus before brassica grazing begins to ensure they are receiving all the essential minerals and trace elements and speak to your vet for advice. Also, ensure animals always have access to fresh water.
Grazing brassicas in long, narrow strips maximises crop utilisation while minimising wastage, trampling and soil damage. If managed well, strip grazing can result in 85-90% crop utilisation. Long, narrow strips also ensure there’s plenty of feed space available so any “shy” animals can graze easily.
Introduce livestock to brassicas slowly over a period of 7 to 10 days, with the time spent grazing gradually increased by an hour or so each day. During this period animals should have access to a lie back area to prevent them needing to be moved to alternative ground.
Protecting ground conditions is important when grazing brassicas during the winter. Strip grazing helps minimise poaching but the correct grazing infrastructure, such as back fences and portable water troughs, is also necessary.
These prevent livestock travelling over the same area repeatedly or moving back over areas they have already grazed. Putting bales in place in the field prior to grazing and before weather conditions deteriorate also helps to reduce soil damage from the impact of machinery.
For more information about grazing brassicas over the winter Click here to watch our webinar: Grazing Brassica Crops.