By Naomi Paley, BSA, PAg, Regional Livestock Specialist, Saskatchewan Ministry of Agriculture and Barry Yaremcio, MSc, PAg, Beef and Forage Specialist, Alberta Agriculture and Forestry
October 12, 2016
With the early snow in Saskatchewan, many acres of annual crops grown for greenfeed are still in the field. There are more concerns now with the time of year and the possibility of not getting the material dry before baling.
Bales containing 18 to 20 per cent moisture (or higher) have the potential to heat. Some of the sugars will be used by the microbes during the heating process. This will reduce the energy content available to the animals. If temperatures within the bale get above 40 C, the bales will smell sweet or like tobacco. The colour can change to dark brown or black. When this happens, some of the protein will be tied to the fiber and not available to the animals. If this occurs, request an Acid Detergent Insoluble Nitrogen (ADIN) or ADIP (protein) test in addition to the regular feed analysis. Use the adjusted lower protein value when formulating rations.
Moulds can also develop in bales with higher moisture. This can result in a loss of quality and possible feed refusal. If mould is present; bales should not be fed through a bale processor but rather rolled out. This will allow the cows to sort through the greenfeed and allow them to waste the material that is contaminated with mould. Forcing cows to eat five per cent mouldy feed can possibly reduce the digestibility of the ration by 10 per cent.
Nitrate could be present in greenfeed if the crop had significant amounts of nitrogen fertilizer or manure applied this spring or last fall. If the crop was cut three to five days after a light frost and the field was well fertilized, this creates conditions favorable for nitrate accumulation in the plant. When bales heat; nitrate can be converted to nitrite (the same first step that occurs in the rumen) making the nitrite 10X more toxic to the animal compared to nitrate. If the bales have slumped and lost normal shape, this indicates that heating has occurred and nitrate to nitrite conversion is possible. Test for both nitrates and nitrites in this situation.
Greenfeed that has been cut for two weeks or longer should not be made into chopped or bale silage. Aerobic bacteria have established themselves in the swath and outcompete the anaerobic bacteria that develop during the ensiling process. White mould can form. Nutrient losses also occur. It is also difficult to make good quality silage with material that has been exposed to the weather.
Applying the appropriate amount of buffered propionic or formic acid to higher moisture greenfeed reduces mould growth and heating. These products could allow baling at four to five per cent higher than normal. Moisture levels remain higher than recommended and these bales should be fed out as quickly as possible.
Higher moisture bales should not be stacked into pyramid piles or under a hay shed. If the bales start to heat, temperatures could get high enough to cause spontaneous combustion. Hay or greenfeed fires are possible.
Bacteria cannot develop when temperatures are below 0 C. One possible option to harvest the greenfeed is to let it stay in the field until temperatures remain below zero and then bale the crop. This is risky because the time available for baling before the crop is completely snowed under may be very short.