Brassica Crops for Hay and Silage

Canola and Mustard Crops for Hay and Silage

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 the taste.

• On a dry matter basis, crude protein averages 12 per cent to 14 per cent, and can be as high as 16 per cent or more.
• Total Digestible Nutrients TDN (energy) averages 55 per cent to 60 per cent, depending on harvest timing.

A feed analysis is recommended to determine actual nutrient values and whether or not nitrates are present. Make sure to include sulphur in the analysis.

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 droop. 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 droop. The plants may take four to six days to dry down to proper moisture levels for baling (16 per cent to 18 per cent moisture content).

Crimping Hay

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 per cent to 80 per cent) and it will take time to wilt them down to 65 per cent moisture. Crimping will hasten the drying process. There may be seepage and ensiling problems if they are ensiled at moisture contents greater than 70 per cent. 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.

Cattle who develop scours

Some producers have noticed that cattle tend to develop scours when fed canola hay or silage as the only source of roughage.

Recommendation

• Canola, mustard hay or silage should comprise no more than 40 per cent to 50 per cent of the total feed intake;
• Canola contains high levels of sulphur (0.5 per cent to 1.3 per cent on a 100 per cent dry matter basis);
• Feed test to determine proper inclusion levels.

The National Research Council publishes the Nutrient Requirements of Beef Cattle. It recommends that total dietary sulphur not exceed 0.4 per cent on a dry matter basis. If cattle diets exceed this level of sulphur 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 per cent 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, should be added to rations containing brassica forages or silage to prevent copper deficiency.
• In some situations, high levels of dietary sulphur create large amounts of hydrogen sulfide gas in the rumen. This can lead to sulphur-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, caused by the consumption of large amounts of actively growing canola forage. 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. No other feed sources were available. In these situations, the plant material undergoes rapid digestion in the rumen. Rumen pH is lowered. In the acidic environment containing high levels of sulphur, large volumes of hydrogen sulfide are produced. Hydrogen sulfide and free sulfide radicals affect cellular energy systems. This causes death of cellular tissue, especially in the grey matter areas of the brain, resulting in PEM.

Sulphur is present in groundwater as well as in feed. It is vital to check the sulphur level of both the feed and the water to avoid the cumulative build up of sulphur 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 herbicides, insecticides or fungicides. Read and follow label directions.