Safe storage of high moisture crops
- Details
- Published on Friday, October 10, 2014
By Elmer Kaskiw
Manitoba Agriculture, Food and Rural Development
There has been some good harvest progress over this past week, although much of what has been harvested has been taken off at damp and tough moisture levels. The overall cereal harvested is now estimated at 70 to 75 per cent complete, although there are extremes at either end of this estimate, while the canola harvest is now estimated at 50 to 60 per cent complete.
Quality loss is now being noted in most spring wheat samples. Canola, for the most part, has cured well after the recent rains, with no significant issues with green seed and generally above long term average yields being reported. Little oats to date have been harvested, however early reports are indicating good bushel weights and above long term average yields. The majority of soybeans have now reached physiological maturity and look to have above average yield potential.
Temporary storage of high moisture canola
A lot of calls over this past week have been in regards to how long one can safely store high moisture canola, testing in the 12 to 15 per cent range, before it begins to cause storage problems. Unfortunately, there are no defined rules in regards to safe storage of high moisture canola since there are so many variables involved which can influence the length of safe storage. Grain temperature is likely the most critical factor, with colder grain temperatures generally allowing for longer safe storage and is why the presence of aeration is so important. Generally, if grain temperature can be kept below 10 degrees Celsius uniformly throughout the bin, then moisture contents of 12 to 14 per cent can be kept for longer periods of time, although careful monitoring and bin turning are still necessary prior to supplemental heat air drying occurring. Aeration will do little in the way of drying once the grain and outside air temperature reach similar levels.
Bushel weight
loss in wheat
Every time a dry ,mature wheat seed is re-wetted by rain or even heavy dews, it will lose test weight. The reason for this is that when a wheat seed has dried down for the first time to safe storage levels, it will have a very smooth outer surface or pericarp. Once the seed is re-wetted and takes on moisture, it develops microscopic wrinkles which pushes up the pericarp, meaning fewer seeds per measured volume and therefore lighter test weights. The more often the seed is re-wetted, the greater the level of wrinkles and the lower the test weights. It is estimated that each time the seed is re-wetted and dried, it will lose an approximate 1 pound per bushel of test weight.
Greenfeed and nitrates
The cool temperatures and relatively light frosts over the last couple of weeks have put an end to this year’s growing season. The only crops that were likely still affected by the frost and cool temperatures were the late seeded greenfeed crops which may have an accumulation of nitrates. Green feed fields at risk to higher nitrates will be ones which have had a higher level of nitrogen fertilizer or manure applied. Alfalfa stands are not at risk of high nitrates since they fix their own nitrogen on an as needed basis. One of the best ways to avoid high nitrates in greenfeed is to leave taller stubble when cutting. Nitrate accumulation is highest at the base of the plant, near the soil surface, so by cutting higher, the majority of the nitrate problem can be left in the field.
Under normal conditions, cattle convert the nitrate in forage to nitrite which is then converted to ammonia and used by microbes in the rumen to make protein. The problem with high nitrates arises when nitrates convert to nitrites faster than the nitrite can be converted to ammonia. When this occurs, the nitrites accumulate and are absorbed into the bloodstream where it binds to haemoglobin reducing the oxygen carrying capacity of the blood. The animals will suffer from a lack of oxygen and die of asphyxiation. Symptoms of lethal nitrate poisoning include difficult breathing, frothing at the mouth, muscle tremors, difficulty in walking and general weakness. Death can occur relatively quickly, within three and four hours. Post mortem examinations reveal dark chocolate coloured blood. Sub lethal doses may result in general loss of appetite, reduced milk production, reduced rates of growth and abortion in bred cows due to a lack of oxygen to the fetus. Ruminants have different capacities to convert nitrate into nitrite and finally to ammonia. Sheep have the highest tolerance to nitrates while cattle have the lowest capability and therefore are at greatest risk. Horses and pigs are monogastric and more tolerant to high nitrate feeds since they convert nitrate to nitrite in the intestine, closer to the end of the digestive tract, where there is less opportunity for the nitrites to be absorbed by the blood.
In order to feed high nitrate forages safely, be sure animals are well fed before introducing the feed. The idea is to slowly get the animals accustomed to the feed so that they can become less affected by the nitrate that is present. The microbes in the rumen are able to adapt to a constant level of nitrate in the feed and make the nitrate conversion cycle more efficient and is why it is important to provide a ration that contains a relatively constant amount of nitrate in the diet, versus constantly switching from high to low nitrate feeds. If you suspect high nitrate feeds an indicator test can be done at your local Ag office.
