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- Annual forage brassicas can provide fast-growing, high yielding, quality fall pasture. Brassicas include cabbage, cauliflower, kale, rape, radish, turnip, rutabaga and swede. They have been used in Europe as livestock forage, for at least 600 years.
- Brassicas tolerate temperatures down to -5 degrees C and are well adapted to the cool, northern parts of Canada. Forage brassicas grow best on well drained soils with a pH of at least 6.
- Typically the crude protein content of kale and rape leaves ranges from 18 to 25 per cent and that of turnip and swede roots from 9 to 10 per cent.
- Brassica forages are generally used for late fall pasture, but on occasion are chopped and fed to reduce the wastage caused by livestock trampling the crop.
- Turnips have bushy tops and large white roots that are rich in carbohydrates. Many varieties can be grazed twice, once for top growth (near the end of summer) and then later for the roots. Turnip has a lower dry matter yield than rape or kale.
- Marrowstem kale has very digestible leaves and stems, and grows to 5 ft (1.5 m) under cool, moist conditions. Dry matter yields of kale range from 4,500 to 7,100 lb/ac (5000 to 8000 kg/ha) and grazing can begin in late summer.
- There are two kinds of forage rape, a giant type which is leafy and upright and a dwarf type which is short and branched. The giant types are used for cattle and sheep pasture while the dwarf types are best suited for finishing lambs. The giant types of rape have higher yields and are more palatable than the dwarf ones. Rape is usually ready to graze about eight weeks after establishment. Forage rape is not the same as oilseed rape or canola.
- Forage brassicas should be established in the same manner as canola. Ensure that the seedbed is firm and do not seed deeper than 0.5 in. (1.5 cm) or alternatively, seed with a zero-till drill into pastures or grain stubble.
- Seeding rates can be as high as 4.5 lb/ac (5 kg/ha) if a problem with weeds is anticipated. Seeding kales and turnips later than mid-June usually results in decreased yields. The later seeding dates for rape ensures that adequate forage is available in September.
- Moderate levels of potassium and phosphorus are required and about 18 lb/ac (20 kg/ha) of sulphur is essential for productive growth. Under irrigation, adequate amounts of naturally occuring sulphur should be available in the water.
- Any mineral supplementation that is used should ensure that the calcium-to-phosphorus ratio in the feed does not exceed 7:1. In addition, a diet containing forage brassicas must be balanced with dry feed to maintain adequate fibre because of the low dry matter content of brassicas.
- Livestock can suffer from rape poisoning if they graze stunted, low growing, purple brassicas. This occurs when the crop is grown under very wet conditions on poorly drained soils, inadequate amounts of fertilizer have been used or an early frost occurs.
- Strip grazing with the use of electric fencing is recommended for brassica pasture, especially kale, for a more uniform grazing, increased gains per acre and to reduce trampling losses.
Brassicas for Forage
- The location of fields, shelter, fencing and water needs to be considered to grow successful crops that are grazed by cattle late in the season.
Extending the Grazing Season with Turnips
Forage Brassicas - Ontario
Grazing Cover Crops: Toxicity Considerations
Use of brassica crops to extend the grazing season
ACS - C12 summer turnip rape - available in PDF format only
Potential of warm-season annual forages and Brassica crops for grazing: A Canadian Review - available in PDF format only
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