Another drawback is that canola contains high levels of sulfur (0.5 to 1.3 percent on a 100 percent dry-matter basis). Producers need to remember that well water and byproducts such as distillers grain also may have high levels of sulfur, Schroeder says. The National Research Council recommends that total dietary sulfur not exceed 0.4 percent on a dry-matter basis.
If cattle diets exceed recommended levels of sulfur intake, several things may occur:
* Cattle fed canola and related crop roughages long term as the sole source of feed may develop hemolytic anemia. Feeding at levels of 50 percent or less should prevent this condition.
* Feeding canola and related forages to cattle for long periods may inhibit their use of trace minerals, particularly copper and selenium. Producers should add fortified trace mineralized salt and various mineral supplements to their cows' diets to ensure the animals receive the recommended levels of copper and selenium on a daily basis.
* In some situations, high levels of dietary sulfur create hydrogen sulfide gas in the rumen. This may lead to polioencephalomalacia (PEM), a dietary disease that can cause lesions to form in the brain. Clinical signs include a lack of muscle coordination, facial tremors, teeth clenching, circling, stupor and cortical blindness followed by the animals leaning or lying down, convulsions and death.
Producers also need to be aware of any pesticides or herbicides that were applied to the crops they plan to use as feed. Remember, the original intention was not to raise the crop for feed. Double-check the pesticide application records to confirm any usage or withholding restrictions are met.
Schroeder says another challenge of using canola as forage is that newly harvested canola stubble provides limited nutrition for grazing (around 6 percent protein). The nutritional value increases considerably when late-summer rainfall produces green regrowth from germination of seed remaining in the stubble.
Also, green canola regrowth subjected to moisture stress during summer 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 growers have reported an unidentified toxin has resulted in sheep losses.
Despite these potential problems, canola hay and wrapped silage or baleage can be a valuable feed source if producers follow some precautions when introducing these feeds to their stock, Schroeder says.
According to Australian research, canola hay and silage from failed or frosted canola crops has been fed to livestock for more than 15 years. Most of the reported problems have involved only a small number of animals from each herd, and almost all of the problems have been associated with a rapid change of diet.