Forage brassica crops play a very important part in livestock grazing and finishing systems in Tasmania, across the dairy, lamb and beef sectors. These crops are relatively easy to grow and provide valuable feed at times of the year when pasture growth is poor such as summer and winter.
Why grow forage brassicas?
Forage brassica crops have very high digestibility and well balanced crude protein levels (typically 12-14%). The production of such high quality feed can greatly assist the timely finishing of livestock and can also help maintain animal growth rates during times of slow pasture growth.
They are also an extremely useful tool when used as part of a pasture renovation program, giving farmers the option of sowing new pasture down in autumn (after a spring sown crop grazed over summer such as bulb or leafy turnips) or in the following spring (after an autumn / winter grazed crop such as rape, kale or swedes).
Points to consider when choosing to grow forage brassicas
The recommended sowing time for forage brassicas in Tasmania is once the soil temperatures are beginning to warm up and have reached 12 degrees or above, this is from early October through until late December, depending on soil moisture or access to irrigation.
It is highly important when choosing which forage brassica species and variety to sow that only certified seed is used. This ensures that you are purchasing seed which is true to type and which meets extremely strict standards on purity and germination.
Selecting seed which has also been treated with a registered insecticide provides valuable protection for new plants. Kickstart™ treated seed provides 4-6 weeks protection for newly emerged brassica seedlings against a range of sucking and biting insects.
Types of Brassica Forage Crops
There are five types of forage brassica crops grown in Tasmania; forage rapes, bulb turnips, forage kales, leafy turnips, sometimes referred to as hybrid brassicas, and swedes.
Forage rapes provide multiple (2-4) grazings 10-12 weeks after sowing and are ideal for finishing lambs over summer and early autumn.
Mainstar is a new “shorter type” forage rape cultivar with increased leaf percentage which provides superior yields of high quality palatable feed over existing rapes. In trial and evaluation work carried out last season it has been observed that livestock have preferentially grazed Mainstar over other forage rape varieties, sown alongside them and growing under the same conditions.
Another proven variety in Tasmania is Winfred.
Bulb turnips are a good option in dairy or beef grazing situations, providing large amounts of quality feed (from the tops and the bulbs) 10-16 weeks after sowing (depending on varieties). A number of varieties suited to and proven in Tasmania are available including Australian Purple Top (offering maturity in 12-14 weeks).
Forage kale is a feed best utilised by cattle and is slower growing than forage rape (maturity is 18-24 weeks). It provides a large amount of quality feed from a single grazing and is ideal for over wintering dairy stock or for beef cattle grazing situations. Sovereign kale is a medium to tall variety providing a high leaf to stem ration and finer stems than other varieties on the market. In trial work Sovereign has shown better utilisation and therefore less wastage than other kales on the market.
Leafy turnips/hybrid brassicas provide high quality feed quickly which provides a useful option for mixed farmers between cash crops or as part of a pasture renovation program. Hunter forage brassica produces high quality feed which can give very good live weight gains especially in lambs. Offering early maturity, with grazing beginning 6-8 weeks after sowing, means feed can be utilised by stock quicker. Hunter also provides rapid regrowth after grazing and in most situations can provide 3-4 grazings, depending on sowing time and available moisture over the grazing period. Due to its faster growing period, Hunter can be a particularly useful crop in a pasture renovation phase, allowing new pasture to be sown earlier in the autumn, resulting in a more established pasture heading into winter.
Swedes are another option for winter feed, either for sheep or cattle in higher rainfall areas. They are high yielding and have a longer growing season than turnips, providing good quality, nutritious feed. Traditionally swedes have been grown in higher elevation/rainfall areas in the state for beef cattle grazing over winter. There is considerable potential for swedes to be used to over winter dairy cattle in the dairying regions of the state, based on experience from New Zealand. Domain swede is a new yellow fleshed variety which is earlier maturing, offering grazing 24-30 weeks after sowing.
Take Home Messages
Campbell S, Knox J, Thompson R (2006) Species for Profit; A guide for Tasmanian pastures and field crops; p 51-62.
SPS Spring Forage Guide (2017); p 4-7; p 18-22.