By Ellen Crawford
Canola can be a feed source if producers follow some common-sense precautions when introducing it to their livestock.
Dairy producers facing forage shortages may be able to feed their cows canola and related crops, provided they take certain precautions, according to a North Dakota State University dairy expert.
Drought in western North Dakota has livestock producers desperate for much-needed forage. Dairy managers are particularly concerned about feed shortages because they rely on high-quality forage to make milk.
For western North Dakota producers, crop aftermath, crops zeroed out for insurance purposes and regrowth of harvested crops stimulated by late-season rains may offer additional forage for certain classes of livestock. Crops that could be fed to cattle include canola and related crops such as brown, yellow and Oriental mustard.
“While these crops make palatable feed, it may take one or two days for cattle to become accustomed to their taste,” says J.W. Schroeder, NDSU Extension Service dairy specialist.
Crude protein in these crops usually is 12 percent to 14 percent and total digestible nutrients (energy) are 55 percent to 60 percent. However, the values can vary, so producers should have a feed analysis on the forage they plan to use to determine actual nutrient values, Schroeder says. He also recommends producers have the forage analyzed for mycotoxins, plus nitrates and sulfur, because they can contribute to serious health problems in cattle.
Canadian producers indicate that rapeseed forage under good growing conditions can be similar to alfalfa in nutrient content. Canola is a rapeseed crop.
Schroeder says that if canola is hayed, drying time is critical to avoid moldy feed later. Typically, the plants take four to six days to dry to proper moisture levels (16 percent to 18 percent moisture content) for baling. Canola tends to turn dark as it cures, but this shouldn’t affect palatability.
However, cattle resist eating stemmy canola forage, Canadian producers report. They believe the forage is unpalatable because of its high sulfur content. Some producers also noted that dairy cattle diets high in canola forage resulted in an undesirable taste to the milk.
“Given the high cost of fuel, evaluate the field closest to you before spending money to bale and haul what might have limited use,” Schroeder advises dairy producers.
A better option may be to ensile the canola if it is leafy and has some height, he says, although canola is high in moisture (75 percent to 80 percent) and wilting it to 65 percent 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 percent.
Some producers have had good results by filling the silage pit with alternating layers of canola and cereal crops cut for silage. This helps reduce seepage problems and offers the opportunity to mix the layers when feeding the silage. The addition of bacterial silage inoculants may be beneficial when ensiling these crops, which are low in soluble carbohydrates.
Also, ensiling will reduce nitrate content by 30 percent to 70 percent, making feeds that are high in nitrate safe to feed.
However, feeding canola creates some risks. Rapeseed, of which canola is a close relative, can cause bloat in some instances. Also, some producers have noticed that cattle tend to develop scours when fed canola hay or silage as the only source of roughage. Schroeder recommends canola hay or silage not be more than 50 percent to 60 percent of the total feed intake.
Another drawback is that canola contains high levels of sulfur (0.5 percent 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 can lead to polioencephalomalacia (PEM), a dietary disease that can cause lesions to form in the brain. Clinical signs include lack of muscle coordination, facial tremors, teeth clenching, circling, stupor and cortical blindness followed by recumbency, 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.
Schroeder says another disadvantage of using canola as forage is that newly harvested canola stubble provides limited nutrition for grazing (around 6 percent protein). However, where late-summer rainfall produces green regrowth from germination of seed remaining in the stubble, the nutritional value increases considerably.
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 problems, canola hay and wrapped silage can be a valuable feed source if producers follow some common-sense 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.
Schroeder has these recommendations for safely introducing animals to canola hay or silage:
Source : ndsu.edu
- Do not offer large amounts of canola hay or silage to stock. Introduce it slowly by replacing a part of the diet by increasing the proportion of canola fodder during a period of days or blending it in a total mixed ration.
- For contained stock, try to offer a mixture of fodder types, at least for the first two weeks of using canola. Stock with access to dry pasture when introduced to canola fodder should have no problems.
- Watch stock for any signs of nitrate poisoning or sensitivity to light. The symptoms of nitrate poisoning are profuse scouring, sudden drop in milk production, rough coat, and occasionally shivering and staggers. The symptoms of photosensitization are reddening or scabs on the ears, muzzle or other areas.
- Learn all you can about the history of the crop. Ask the grower how much and when nitrogen fertilizer was applied, and the level of drought stress in the crop. Fodder made from crops that were badly stressed or had high applications of top-dressed nitrogen fertilizer may have increased levels of nitrates.