Cool-season legumes (peas) and brassicas (canola, forage rape, forage radish and turnips, and kale) are increasingly being used alone or in combination with cereals in mixtures, polycultures, or cocktail crops.
Mixtures of legumes, brassicas, and cereals have different nutritional value than monocultures and can improve forage quality. Cocktail crops have also been shown to improve soil quality by enhancing diversity of microbial populations, which in turn can help improve nutrient cycling.
Peas
- Adapted to the Dark Brown, Black, and Grey soil zones.
- Generally not used for grazing unless included with a cereal.
- When properly inoculated, little or no nitrogen fertilizer is required. In addition, legumes can provide a rotation benefit because about 25 per cent of the fixed N remains in the soil after harvest.
- Cereal/pea mixtures yield similar or slightly less dry matter, but more protein per acre than cereals alone.
- Seed pea/cereal mixtures at a full pea seeding rate with a 30 per cent cereal seeding rate (100:30) to ensure your legume population remains in stand.
- Pea/cereal mixtures at a 50:50 ratio produces a similar or greater yield than a 100:30 ratio, but the proportion of peas will be reduced by 15 to 20 per cent.
- Trials indicate that peas have a better chance of increasing forage protein content if the mixture is seeded on stubble land where the amount of available nitrogen is low.
- In general, application of small amounts (56 kgs./ha) of N fertilizer can increase the dry mater yield of cereal/pea mixtures, but it can also slightly decrease the biological N fixation of pea.
- Forage varieties that would be suitable include CDC Jasper, CDC Horizon, and the forage pea variety 40-10.
Forage brassicas grow best on well drained soils with a pH of at least 6, and they should be established in the same manner as canola. Brassicas tolerate temperatures down to -5 C and are well adapted to all parts of Saskatchewan.
Care should be taken when introducing livestock to brassica feed or mixtures.
Excessive brassica intake can cause rapid movement of feed through the digestive tract. When brassicas are used as greenfeed, hay or straw supplementation is required to increase fibre uptake or, if used for late fall pasture, they should be seeded in combination with cereals.
Brassicas accumulate sulphur, frequently exceeding 0.4 per cent of dry matter for beef cattle, which can cause B-vitamin-deficiency and increase risk of polioencephalomalacia (PEM). High sulphur intake can also induce trace mineral deficiency (e.g. copper) in cattle. Risk of damage caused by glucosinolates is greater among young animals.
Most forage brassicas do not meet copper, zinc, and manganese dietary requirements for ruminants, so mineral supplements are required. Iodine, iron and copper supplements help to prevent anemia and goiter. When mineral supplements are used the calcium-to-phosphorus ratio in the feed should ideally be 2:2 but must not exceed 6:1.
To reduce the chances of PEM or mineral deficiencies when no test is available to develop a balanced ration, brassicas should make up no more than 50 per cent of the dry matter intake. An example of this type of diet would be 6 kg of canola hay, 8 kg of alfalfa hay and 65 grams (2 to 4 ounces) of a 14:14 beef mineral and 30 grams (1 ounce) of salt.
Brassicas can also can cause nitrate poisoning if grazed when purple and stunted, under very wet conditions on poorly drained soils, with inadequate fertilizer, or when an early frost occurs.
Strip grazing with the use of electric fencing is recommended for pasture that includes brassicas, especially if it includes kale, to reduce trampling losses
Canola
- All varieties of canola and mustard except industrial-use oils can be grazed, hayed, or cut as greenfeed.
- When cut at the early to mid-pod stage of development, canola quality is comparable to good-quality alfalfa-grass forage.
- Crude protein averages 15 per cent with total digestible nutrient values averaging 58 per cent on a dry matter basis.
- Quality of damaged or stressed canola can be significantly lower than average, so a feed test for nitrate and sulphur should be conducted prior to feeding.
- Ensure that the canola feed does not contain chemical residues that could impact the health and performance of the cattle or render meat unsaleable.
- Canola cut near maturity tends to be coarse and stemmy, reducing its quality and palatability.
- It may take seven to 10 days to dry prior to baling and should be crimped to hasten the drying process.
- Canola feed should be introduced slowly by replacing part of a more conventional diet over a week or more, while monitoring for abnormal behaviour, until cattle become accustomed to it.
Forage rape
- Do not confuse with oilseed rape or canola.
- There are two kinds: a giant type that is leafy and upright, and a dwarf type that is short and branched.
- Giant types are used for cattle and sheep pasture, while the dwarf types are best suited for finishing lambs.
- Giant types have higher yields and are more palatable than dwarf varieties.
- Rape is usually ready to graze about eight weeks after establishment.
- Protein content is similar to that of Kale.
- Dry matter yields of giant types grown under irrigation can reach 8900 lb./ac. (10,000 kg/ha).
Forage radish and turnips
- Very cold-hardy and frost-resistant.
- Lush growth and high in protein.
- Seed in late July or early August with oats, winter triticale, or fall rye for fall grazing.
- Susceptible to pests and insects, and prone to problems with nitrate accumulation.
- Sensitive to carry-over residues of some herbicides.
- There may be a choking hazard when livestock eat the tubers.
- Not recommended for dairy animals, as turnips may taint the flavour of milk.
- In mixtures, their rapid regrowth allows for fall grazing when other species in mixtures have finished growing. Livestock consume the leaves and dig out the tubers in the fall.
- Advantageous in dry spells because they will go dormant for as long as 30 days and green up when precipitation resumes.
Kale
- Has very digestible leaves and stems, and grows to 5 ft (1.5 m) under cool, moist conditions.
- Grazing can begin in late summer.
- Crude protein content ranges from 18 to 25 per cent.
- Dry matter yields range from 4,500 to 7,100 lb/ac (5,000 to 8,000 kg/ha).