Ohio State University Extension
Department of Horticulture and Crop Science
2021 Coffey Road, Columbus, Ohio 43210-1044

Brassicas for Forage

AGF-020-92

Forage brassicas are high quality, high yielding, fast growing crops that are particularly suitable for grazing by livestock. Both tops (stems plus leaves) and roots (bulbs) can be grazed and are very nutritious. Brassicas can be seeded (1) from mid April through May for summer grazing or (2) in July or August for fall/winter grazing. All members of the brassica family - turnips, rape, kale, and swedes - produce forage of exceptionally high (often 85-95%) digestibility. Weight gains by stocker cattle and feeder lambs have been 0.2 to 0.4 lbs/day for lambs and 1.5 to 2.0 lbs/day for stockers.

Turnips and rutabagas are short-season root brassicas that provide roots, stem and leaf growth for rotational grazing or strip grazing 70 to 90 days after seeding. The leaves can be grazed from mid- September until January depending upon critical low temperatures and snow cover. Top growth generally will survive temperatures between 15-20 degrees F, while bulbs will be about 5 degrees hardier. The common purple top garden type as well as Rondo, Royal Crown and other forage varieties, yield up to 7000 lb/acre of dry matter. The tops have 17-24% crude protein while roots contain 12-15% protein. Some new forage-type turnip varieties such as All Top produce relatively more top dry matter than roots. Turnips are seeded from mid July to mid August at rate of 2-3 lb/acre and produce maximum yields approximately 90 days after seeding.

Rape is a short-season leafy brassica whose stems and leaves are ready to harvest (rotationally graze, strip graze or green chop) 90- 120 days after establishment. Plants develop a reddish tinge when ready for harvest. Rangi, Windall, Dwarf Essex, Winfred and Emerald varieties have performed satisfactorily in Penn State University trials. Leave a ten-inch stubble to facilitate rapid regrowth. Rape leaves and stems have lower protein level (14-17%) than turnips. Rapes can attain yields of 8000 lb/acre dry matter if planted during May or June. Rape can be planted as late as August 1, but with lowered potential yield if planted late. Seed at 3-4 lb/acre rate.

Kale generally has shown highest yields of all brassicas with up to 12,000 lb/acre dry matter production at 150 days. It has the greatest cold tolerance in the Brassica family, surviving temperatures down to 10 degrees F. This allows grazing of the leaves and stems by rotational or strip grazing into December and January most years. Marrow Stem, Maris Kestral and Premier kale varieties have performed well in trials at Penn State. Average protein content is between 15-17%. Seed kale from early spring to mid July using a seeding rate of 3.5 to 4 lb/acre.

Other brassicas used for forage include: swedes, a long-season root plant providing roots, stems and leaves; rape-Chinese cabbage hybrids and turnip-Chinese cabbage hybrids. Tyfon is an example of a forage type turnip-Chinese cabbage hybrid.

While brassicas have been successfully used for centuries in Europe and other parts of the world for livestock feed, the following precautions should be noted. Brassicas are very high in crude protein and energy, but extremely low in fiber. Their low fiber content results in rumen action similar to when concentrates are fed; thus the need for proper roughage supplementation. Brassicas therefore should never comprise more than two-thirds of the forage portion of livestock diets with the remainder provided by grass hay or stockpiled pasture. Likewise all brassicas contain low levels of glucosinolate compounds. Again, adequate grass forage supplementation seems to prevent them from causing animal health problems. Nitrate poisoning has been documented from excessive nitrogen fertilization plus reported instances of high accumulation of calcium and potassium that can reduce the availability of magnesium to animals. Utilize feed analyses to check and modify mineral balance of animal diets. Excessive fertilization of both nitrogen and potassium should be avoided. Most dairymen have avoided off-flavors in milk by preventing brassica consumption two hours before milking. Others prefer to only feed rapes to lactating dairy animals plus adequate grass roughages.

Strip grazing where forage is rationed every day or two provides the most efficient usage. Rape, kale and mustard have regrowth potential if not grazed below six inches. Turnips will regrow if the growing point at the top of the bulb is not removed. Two or more cycles should be possible with rotational grazing if rainfall is adequate. Rapes, kale and mustard can be green chopped for confined animals.

No-tillage seeding in sod is recommended, but competition from the sod must generally be controlled by herbicides during the first two weeks after emergence. Broadcast spray Gramoxone Extra at 1 1/2 pt/acre + surfactant or 1 qt/A Roundup, one or two days prior to seeding. Once established, brassicas will smother out most weeds. Brassica can be no-tilled into pastures at lower seeding rates so a mixture of brassicas and grass is available for grazing with the grass cover retained to protect the soil during the winter. They also can be seeded with rye which will protect the soil after brassicas are consumed by animals.

A 6 to 8 inch row spacing for both no-tillage and conventional tilled seedbeds is suggested. Seed can also be broadcast and incorporated by cultipacking. Brassicas should not be seeded more than 1/4 to 1/2 inch deep. If seeding into tilled seedbeds, plow the ground at least six weeks before sowing with enough secondary tillage to develop a firm seedbed free of weeds and soil clods. Brassicas are not adapted to wet, poorly drained sites and grow best on well drained soils that have a pH between 5.3-6.8 and medium levels of phosphorus and potassium. Apply 50-75 lb/acre of nitrogen at time of seeding or within three days to hasten seedling emergence. Brassicas should not be grown on the same site for more than two consecutive years to prevent buildup of stand-threatening diseases. Use appropriate insecticides if flea beetles or other insects become severe. Brassica quality remains high until vegetative growth ceases. Thereafter fungal diseases may develop following crop maturity that can cause losses in quality.

In 1989, the authors conducted a replicated field trial (sown on July 10) in Perry County. The summer planting date favored the shorter-season turnips and mustard compared to the longer maturity kale and rape entries. Table I presents yield information from harvests made on October 17.

Table I. 1989 BRASSICA STUDY - PERRY COUNTY

During 1990, ten cultivars, including six in the previous year's study, were evaluated in a replicated trial in Hocking County. This trial was planted on July 25 and yield harvests made on October 26.

Table II. 1990 BRASSICA STUDY - Hocking County

Again, the later planting date and single fall harvest favored yields of turnip and rutabaga yields over kale, rape and mustard. The latter require May-June planting and multiple grazing/harvests to achieve maximum yields. Forage Star turnip repeated as top producer with nearly 3 T/A yield of dry matter. Comparison of the six entries sown both seasons showed similar root production, but higher topgrowth yields during 1990.

Brassicas offer a means for some Ohio livestock producers to produce high quality forage either (1) during the critical summer period of slowed pasture growth and/or (2) to extend grazing into the late fall-early winter period.

Prepared by:
Henry M. Bartholomew
County Extension Agent, Agriculture
Perry/Hocking Counties

John F. Underwood
District Agronomy Specialist