Brassica Crops for Hay and Silage (Canola and Mustard)

January 2008

Canola and Mustard (brown, yellow and Oriental) can be fed to cattle provided certain precautions are taken. While these crops make palatable feed, it may take one or two days for cattle to become accustomed to their taste. On a Dry Matter Basis, Crude Protein averages 12% to 14%, and can be as high as 16% or more. Total Digestible Nutrients TDN (energy) averages 55% to 60%. A feed analysis is recommended to determine actual nutrient values and whether or not nitrates are present. Make sure to include sulfur in the analysis.

To maximize total Dry Matter yield and maintain good protein and energy levels, the crops should be cut any time from the early podded stage just after the flowers have dropped, up to the stage where the lower leaves are starting to drop. 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. The plants may take four to six days to dry down to proper moisture levels for baling (16% to 18% moisture content). Crimping the hay ensures faster and more uniform drying. Canola tends to turn dark as it cures, but this does not seem to affect palatability. If canola is cut near maturity its feed value will be similar to that of cereal straw. Cattle do not find this type of feed palatable and it is best used as bedding unless it is processed and mixed with other hay.

Canola and mustard can be used for silage. These crops are high in moisture (75% to 80%) and it will take time to wilt them down to 65% moisture. Crimping will hasten the drying process. There may be seepage and ensiling problems if they are ensiled at moisture contents greater than 70%. Some producers have had good results by filling the silage pit with alternating layers of canola and cereals cut for silage. This helps to 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.

Some producers have noticed that cattle tend to develop scours when fed canola hay or silage as the only source of roughage. It is recommended that canola or mustard hay or silage comprise no more than 50% to 60% of the total feed intake. Canola contains high levels of sulfur (0.5% to 1.3% on a 100% Dry Matter basis). The National Research Council publishes the "Nutrient Requirements of Beef Cattle". It recommends that total dietary sulfur not exceed 0.4% on a dry matter basis. If cattle diets exceed this level of sulfur intake, several things may occur.

• Cattle fed long-term diets of these roughages as the sole source of feed may develop a condition called Haemolytic Anaemia. Feeding at levels of 50% or less should prevent this condition from occurring.
• Feeding brassica forages to cattle for long periods may inhibit the utilization of trace minerals, particularly copper and selenium. Ensure that recommended levels of copper and selenium are fed on a daily basis. Fortified trace mineralized salt and various mineral supplements contain varying levels of copper and selenium. These should be added to rations containing brassica forages or silage to prevent copper deficiency.
• In some situations, high levels of dietary sulfur create hydrogen sulfide gas in the rumen. This can lead to sulfur-induced 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. These conditions are soon followed by recumbency, convulsions and death. Fatal cases of PEM have been confirmed in Saskatchewan which were caused by the consumption of large amounts of canola forage with high sulfur levels. Several noted cases have occurred when cattle were grazing canola re-growth in the fall. The canola plants were in the rosette stage. The fibre content of the plants was low with high moisture levels. It was suspected that the sulfur was highly soluble. No other feed sources were available.

Sulfur is present in groundwater as well as in feed. It is vital to check the sulfur level of both the feed and the water to avoid the cumulative build up of sulfur in the rumen.

It is also important to note which pesticides were applied to the crops prior to their use as feed. A number of grazing and feeding restrictions may apply to crops treated or sprayed with pesticides or herbicides.  Read and follow label directions.

For more information, contact:
Agriculture Knowledge Centre
Saskatchewan Agriculture
Toll Free:  1-866-457-2377
E-mail:  aginfo@gov.sk.ca