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Drought-stressed canola possible forage for livestock

It can work as an emergency source, but some risks need to be managed

While it is important to be aware of risks associated with feeding canola forage, it may provide an alternate forage for drought-stricken livestock producers.

Drought stress has resulted in poor canola stands that are unable to be harvested. Poor canola stands may provide an alternate forage option.

“Livestock producers facing forage shortages may be able to feed their cows canola, provided they take certain precautions,” says Miranda Meehan, North Dakota State University Extension livestock environmental stewardship specialist. “While canola makes palatable feed, it may take one or two days for cattle to become accustomed to the taste.”

Forage rapeseed (canola) has a nutrient content similar to alfalfa, with crude protein of 12 per cent to 16 per cent and total digestible nutrients (energy) of 55 per cent 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,” advises Zac Carlson, NDSU Extension beef cattle specialist.

It is important to be aware of risks associated with feeding canola forage, which 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,” says Janna Block, extension livestock systems specialist at NDSU’s Hettinger Research Extension Center. “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, which warrants caution when devising feeding plans,” says Carlson. “Producers also need to be aware of any withdrawal periods associated with pesticides or herbicides that were applied to the standing plants.”

See the NDSU publication Nitrate Poisoning of Livestock for more information about elevated concentrations of nitrates in feedstuffs.

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 to grazing animals, including cattle and sheep. 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, according to Meehan. 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.

Carlson notes that cattle may resist eating stemmy canola forage. Using a roller mower/conditioner to smash stems will help reduce drying time and improve consumption.

Block says 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. Canola is high in moisture (75 per cent to 80 per cent) and wilting it to 65 per cent moisture will take time. Harvesting a mixture of the mature stand and the regrowth will reduce the moisture, and crimping will hasten the drying process.

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 (i.e. straw) to the silage pile, bunker or bag.

Meehan advises producers to follow these recommendations for safely introducing animals to canola hay or silage:

  • 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.

For more content related to drought management visit The Dry Times, where you can find a collection of stories from our family of publications as well as links to external resources to support your decisions through these difficult times.

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