Greenfeed that saw snow before being harvested this year presents some extra challenges when feeding.
Bales containing 18 to 20 per cent moisture (or higher) have the potential to heat, and some of the sugars will be used by the microbes during the heating process, said provincial forage specialist Barry Yaremcio.
“This will reduce the energy content available to the animals,” he said.
If temperatures within the bale get above 40 C, the bales will smell sweet or like tobacco, and the colour can change to dark brown or black. When this happens, some of the protein will be tied to the fibre and not available to the animals. If this occurs, Yaremcio recommends requesting an acid detergent insoluble nitrogen (ADIN) or ADIP (protein) test in addition to the regular feed analysis, and to use the adjusted lower protein value when formulating rations.
Moulds can also develop in bales with higher moisture, and 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,” said Yaremcio. “This will allow the cows to sort through the greenfeed and let them waste the material that is contaminated with mould.”
Forcing cows to eat feed with five per cent mould can reduce the digestibility of the ration by 10 per cent.
Nitrate in greenfeed is another concern, and it could be present 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 favourable for nitrate accumulation in the plant,” said Yaremcio.
When bales heat, nitrate can be converted to nitrite (the same first step that occurs in the rumen), making the nitrite 10 times more toxic to the animal compared to nitrate. A telltale sign of heating and possible nitrate-to-nitrite conversion is if the bales have slumped and lost normal shape. He recommends testing for both nitrates and nitrites in this situation.
Yaremcio also advises against making chop or bale silage out of greenfeed that has been cut for two weeks or longer. This is because aerobic bacteria have established themselves in the swath, and will outcompete anaerobic bacteria during the ensiling process. White mould can form and nutrient losses also occur. It is also difficult to make good-quality silage with material that has been exposed to the weather.
One option available to help counter mould growth and heating is applying the appropriate amount of buffered propionic or formic acid to higher-moisture greenfeed. These products could allow baling at four to five per cent higher-than-normal moisture levels. However, these bales should be fed out as quickly as possible.
Bacteria cannot develop when temperatures are below 0 C, so one possible option is to bale the greenfeed when temperatures remain below zero. Nevertheless, this method also has risks because the time available for baling before the crop is completely snowed under may be very short.
Surprisingly, producers should treat higher-moisture bales as possible fire hazards.
“They should not be stacked into pyramid piles or under a hay shed, because if the bales start to heat, temperatures could get high enough to cause spontaneous combustion,” said Yaremcio. “Hay or greenfeed fires are entirely possible.”