Poor canola stands not worth harvesting can be an alternate forage option.
“While canola makes palatable feed, it may take one or two days for cattle to become accustomed to the taste,” said Miranda Meehan, North Dakota State University Extension livestock environmental stewardship specialist.
Forage canola has a nutrient content similar to alfalfa, with crude protein of 12 to 16 per cent and total digestible nutrients of 55 to 60 per cent. Crude protein and energy levels will be higher if the crop is cut in the early-podded stage rather than after the lower leaves begin to drop.
“Nutritional quality can vary, so producers should have a feed analysis on the forage they plan to use to determine actual nutrient values,” said Zac Carlson, NDSU Extension beef cattle specialist.
Risks associated with canola forage include bloat, scours, and elevated levels of sulphur and nitrates. To reduce bloat and scours issues, acclimate cattle for a period and blend the canola with other feeds so canola hay or silage is less than 50 per cent of the total feed intake.
Sulphur levels of canola can range from 0.5 per cent to 1.3 per cent on a dry-matter basis.
“Combining high sulphur from canola with high sulphur from byproducts such as distillers grains can be even more problematic, and producers are encouraged to keep total dietary sulphur below 0.4 per cent on a dry-matter basis,” added Janna Block, NDSU Extension livestock systems specialist. “It is also important to check sulphur levels in water sources to be able to account for all sources of dietary sulphur.”
Feeding sulphur above this threshold can result in hemolytic anemia, interference with livestock’s use of the trace minerals copper and selenium, and polioencephalomalacia (PEM).
Clinical signs of PEM include a lack of muscle co-ordination, facial tremors, teeth clenching, circling, stupor and cortical blindness, followed by animals leaning or lying, convulsions and death.
“Drought stress in canola also can lead to accumulation of nitrates in the plants,” said Carlson. “Producers also need to be aware of any withdrawal periods associated with pesticides or herbicides that were applied to the standing plants.”
Watch the regrowth
Another issue producers should be concerned about is green canola regrowth that was subjected to moisture stress during summer because it can be toxic. Researchers don’t know the exact type of toxin causing the problem, but Australian sheep producers have reported an unidentified toxin has resulted in sheep losses.
If canola is hayed, drying time is critical to avoid mouldy feed later. Typically, the plants take four to six days to dry to proper moisture levels (16 to 18 per cent moisture content) for baling. Canola tends to turn dark as it cures, but this shouldn’t affect palatability.
Cattle may resist eating stemmy canola forage, said Carlson. Using a roller mower/conditioner to smash stems will help reduce drying time and improve consumption.
A better option may be to ensile the canola if leaf area and height are adequate, which should reduce nitrate content by 30 per cent to 50 per cent, said Block. Canola is high in moisture (75 to 80 per cent) and wilting it to 65 per cent moisture will take time.
Seepage and ensiling problems may occur if canola is ensiled at moisture contents greater than 70 per cent. To prevent seepage loss if ensiling, add dry forages to the silage pile.
Meehan advises producers to follow these recommendations:
- Introduce canola hay or silage slowly by replacing a part of the diet over a week to 10 days.
- Have other types of forage available for cattle in confinement for the first two weeks as canola is being introduced.
- Test hay or silage for concentrations of sulphur and nitrates, and formulate rations or design feeding schemes to reduce risks associated with feeding forage canola.