Extend the grazing season with hybrid brassicas
The development of hybrid brassicas has been a significant breakthrough for fodder crop feeding options, offering livestock farmers a versatile option for extending the grazing season whenever other forages are less productive.
Historically forage crops have been regarded as a feed option for livestock in the winter/early spring feeding period. Their high yield potential, nutritional quality and winter hardiness make them an attractive choice for farmers wintering stock outdoors. Traditional crops of choice still include kale, forage rape, swedes, stubble turnips and fodder beet.
Hybrid brassicas have the potential to produce high energy grazing crops within 8 to 10 weeks and also act as an effective break crop in reseeding programmes. The most common hybrids are Redstart and Swift; these are crosses between kale and forage rape which have been developed in New Zealand. The hybrids are very vigorous and grow rapidly, and also have significant regrowth ability; if they are not severely damaged or poached in a first grazing, they will grow again rapidly to give a second and possibly third grazing. This won’t happen in the winter due to low temperatures and severe grazing conditions, but it is a trait that can be taken advantage of in both summer and autumn. In addition hybrid brassicas have a very high nutritional value both in terms of energy and digestible proteins.
Many grassland farms suffer a dip in yield and quality from their swards in mid-summer. This can impact on finishing lambs, cattle and milk production. Hybrid brassicas sown in late April/early May are ideal for filling this grazing gap, as they will be fit to be grazed only 8 to 10 weeks after sowing. They have a yield potential of 4 to 6tDM/ha and offer extremely palatable material. After grazing, the crop can be fertilized and grown again for a mid-October grazing, or alternatively it can be deferred for winter forage. Depending on grazing management, a similar yield to the first grazing is achievable.
Alternatively these crops can be used as a nurse crop to new reseeds. The new leafy, highly digestible grass and hybrid combination provides a high energy feed for finishing lambs, and the intensive grazing management demanded by the crop creates an ideal sward in the new reseed. These crops are block grazed in rotation having been divided into 3 or 4 sections. Lambs achieve their required weights more quickly, reducing the need to finish with concentrates or sell as stores.
Advice for successful use of hybrid brassicas
1. They are small seeds so a fine firm seed bed is essential
2. A vigorous growth habit generally out-competes weeds
3. It is critical to use adequate N and P to realise their yield potential
4. As with all brassicas, trace element supplementation is critical
5. When feeding all brassicas, provide a fibre source to the animals (this is not necessary where they are sown along with grass)
6. Overgrazing or grazing in very difficult conditions will affect regrowth of the crop
7. With good management, hybrid brassicas can be used for several grazings during the summer season or for single grazing as a dedicated winter feed
8. Key varieties are Redstart and Swift hybrid brasssica