5 August 2012

5 minute read

Drought-challenged dairy producers facing forage shortages may be able to feed their cows canola and related crops, provided they take certain precautions.

“Recent rains were spotty, and encroaching drought in North Dakota has livestock producers scrambling for much-needed forage,” says Mr Schroeder. “Dairy managers are particularly concerned about feed shortages because they rely on high-quality forage to make milk. The drought elsewhere will result in greater competition for locally grown forages.”

For 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,” Mr Schroeder says.

If canola is hayed, drying time is critical to avoid moldy feed later, he says. Typically, the plants take four to six days to dry to proper moisture levels (16 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 in 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,” Mr Schroeder advises dairy producers.

A better option may be to ensile the canola if it is leafy and has some height, although canola is high in moisture (75 to 80 percent) and wilting it to 65 percent moisture will take time, he says. Harvesting a mixture of the mature stand and the regrowth will reduce the moisture, and crimping will hasten the drying process.

Also, ensiling will reduce nitrate content by 30 to 70 percent, making feeds that are high in nitrate safe to feed.

However, feeding canola creates some risks. Canola 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. Mr Schroeder says canola hay or silage should not make up more than 50 to 60 percent of the total feed intake on an as-fed basis.

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, Mr 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.

Mr 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.

Mr Schroeder has these recommendations for safely introducing animals to canola hay or silage:

• Do not offer large amounts of canola hay or silage to stock. Introduce it slowly by replacing a part of the diet and increasing the proportion of canola fodder during a period of days, or blending it in a total mixed ration.
• For confined 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, a 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.

August 2012