Spring sowing – forage brassicas
A growing number of producers are taking advantage of forage brassicas to fill seasonal feed gaps and provide a high-quality, economical feed option for their livestock.
Forage brassicas bring many benefits to grazing systems. With a sowing rate of 3-5 kg/ha, they are a cheap way to accumulate a large amount of feed. With growth rates similar or quicker than most forage cereals,1 they can rapidly accumulate biomass. However, the real strength of brassicas is their superior feed quality and their ability to retain this quality throughout the season. Quality parameters are often in the range of 11-12.5 megajoules of metabolisable energy (ME) and 15 to 22 per cent crude protein with a low fibre content.1 This makes them a suitable feed source for lactating dairy cows, finishing lambs, growing steers, or improving the condition of breeding stock.
Another strength of brassicas is their wide adaptation to different environments and soil types, from sands to heavy clay. They do, however, require good levels of nitrogen, phosphorus, and boron and rely on accurate seeding depth (5 to 10 mm) for optimal establishment. Combining this broad adaption with a flexible sowing window from late winter right through to autumn makes forage brassicas an excellent option for most systems.
Which type of forage brassica should I choose?
There are different types of forage brassicas on the market, including bulbed and leafy turnips, forage rape and hybrids, kale and radish.
Each has a unique fit depending on your requirements. If super quick feed is what you are looking for, S&W’s Bouncer Forage Brassica is a leafy turnip ready to graze in as little as five to six weeks. Bouncer provides multiple grazing opportunities without the maturity requirement. It is well suited to dairy systems or more intensive beef and sheep enterprises with high soil fertility and rainfall.
Bouncer can lose palatability if grazing is deferred for longer than eight to nine weeks, so if you require bulk feed later in the season, S&W Subzero Forage Brassica is the option for you. Subzero is a quick maturity forage rape and kale hybrid. It has the flexibility to be ready to graze early, eight to 10 weeks post-sowing, with good regrowth potential, while also maintaining quality for a bulkier graze later in the season. Subzero is a tough variety handling both periods of moisture stress and cold, frosty conditions exceptionally well. This makes it suitable for large, extensive grazing systems or more intensively managed beef, sheep, and dairy enterprises.
How to calculate crop requirements
Let’s say you have 100 young steers that you want to feed from December to February on a crop of Subzero Forage Brassica and Rebound Millet. We step you through how to calculate your requirements.
- A 250kg steer, gaining 1 kg/day has a DSE rating of 9.
- Maximum daily feed intake = 0.8 x DSE (or use 1.2 X liveweight ÷ NDF%)
- The crop provides the energy, protein, and fibre requirements for this class of stock and has grown 8 t/ha of Dry Matter (DM).
- Allow 30 per cent wastage in a set stocked grazing system.
Step by step calculations
Step one: how much crop?
Intake = 0.8 x 9 = 7.2 kg DM/head/day
7.2 kg + 30 per cent wastage = 9.4 kg DM/head/day
9.4 kg x 100 head = 940 kg DM/day
940 kg x 100 days = 94 tonne to fully feed all steers
94 t ÷ 8t/ha supplied = 11.75 ha required
Step two: What’s the cost?
In addition to the cost of seed, you should also consider the cost of additional inputs such as knockdown herbicide/insecticide, lime and fertiliser, cultivation/contractor.
Bouncer is available from your local Elders branch.
 Bell, L. W., Watt, L. J., & Stutz, R. S. (2020). Forage brassicas have potential for wider use in drier, mixed crop-livestock farming systems across Australia. Crop & Pasture Science, 71 (10), 924-943.
Article written by S&W Seed Co for Seasons magazine.