With the dry weather this year and low forage yields across much of the province, many producers are looking for alternative forages. There is a lot of stressed corn that could be utilized as forage for livestock. The amount of moisture stress that the corn has been through can affect the quality of the silage and there can be great variability between fields and even within a field. In fields that were dry during tasseling or pollination and have reduced grain fill, the energy content of the silage will be reduced but forage quality should remain constant. When feeding this forage to animals, it is very important that a feed test is done so that the nutritional composition of the silage can be adjusted for in the ration.
When negotiating the price for selling standing corn as silage, the final price is typically somewhere between the net income that could be received from the grain and the value of the forage. The minimum price for corn silage would be the net income that could be obtained by selling the grain, and the value of the phosphorus and potassium that are being removed by the stover. When estimating yield, it is best to be realistic and look at different points in the field to take into account any variability. Corn silage pricing may also take into account the availability of other forage sources in the area, distance from field to storage, storage costs, and anticipated losses from fermentation and storage. Sellers with a potential Crop Insurance claim should contact Agricorp (1-888-247-4999) before harvest to determine how selling corn as silage will impact the claim.
Moisture stressed corn can be harvested either by grazing, green chopping or fermenting into corn silage. If the corn field has a good perimeter fence, then grazing moisture stressed corn may be an option. When grazing animals on corn stalks, they will eat the cobs first and then the leaves and the stalks above the cobs. The field should be strip grazed with pastures sized so the animals are allowed to have no more than 2 days worth of feed at a time. It is important to ensure that animals grazing corn stalks have mineral available and an adequate water supply. In certain cases it may be necessary to supplement with grain and/or hay. Any animals grazing corn need to be monitored for grain overload or acidosis.
When chopping stressed corn for silage, it is important that it is harvested at the right moisture level. Typically moisture level can be estimated from the milk line, but with the dry weather this year, the whole plant moisture will not correlate with milk line as closely as in a normal year. In order to obtain accurate moisture levels, at least 10 random plants should be sampled, chopped and then tested using a Koster tester, microwave test, or an accredited lab. Harvesting corn silage when it is too dry can result in insufficient packing, poor fermentation, heating, mould and spoilage. Moisture contents greater than 70% can cause seepage and clostridia fermentations that produce butyric acid, resulting in high fermentation losses, lower intakes, ketosis and poor cow performance.
When working with moisture stressed corn, it is necessary to monitor it for nitrate levels. Nitrate poisoning occurs when there are high levels of soil nitrates and environmental conditions that cause them to accumulate in plants. Nitrate poising is particularly high risk during the 5 – 7 days following a rain that ends a severe dry period. Avoid grazing or green chopping during this period. Making silage from drought stressed corn can greatly reduce the risk of nitrate poisoning as the levels of nitrates are reduced during fermentation. When nitrate levels are high, they increase the level of nitrogen dioxide (silo gas) that is produced when corn is ensiled.
When animals consume nitrates, the rumen will convert them to nitrites. High levels of nitrites impair the ability of blood hemoglobin to carry oxygen. Symptoms of nitrate toxicity include rapid breathing, fast and weak heartbeat, difficult breathing, muscle tremors, staggering and death. If you suspect nitrate poisoning, keep the animals quiet and comfortable and call your veterinarian immediately. Less affected animals may be listless and show more subtle symptoms including poor appetite, reproductive problems (including abortion) and poor performance.
Feed samples can be taken to test for nitrate (NO3) or nitrate-nitrogen (NO3-N). As a general rule nitrate-nitrogen levels should be less than 1,000 ppm (NO3 levels <0.44%) to be without risk. Levels greater than 4,000 ppm NO3-N (>1.76 % NO3) are potentially toxic and should not be fed. Rates between these two levels are somewhat toxic and should be carefully managed. Corn should not be grazed unless the nitrate levels are within safe levels. More information on nitrate levels can be found by checking the factsheet: Potential Nitrate Poisoning and Silo Gas When Using Corn Damaged by Dry Weather for Silage, Green Chop or Grazing (http://ontario.ca/cwo1 )