 |
|
|
|||||
|
|
September 29, 2005 Determining Moisture Content of Forages Important The recent loss of forage from heating and fire is a reminder of the importance of monitoring the moisture of forages going into bales or a pile, as well as into the cow, according to J.W. Schroeder, North Dakota State University Extension Service dairy specialist. He says that while most of the haying is done for this year, knowing the moisture and dry matter (DM) content of feeds is important to farmers and ranchers for several reasons. They include: Livestock performance depends on DM consumed; moisture content is essential for harvest decisions during haying or silage production; and moisture content often is related to determining the value or price of the forage crop. Several methods are available to test moisture content of forages. Producers often use meters and probes, but that equipment becomes unreliable when moisture content is higher than 25 percent. The density of the forage, source of the moisture in the forage and operator skill will affect the accuracy of probes and meters greatly. Schroeder says that drying by evaporating water from a sample can provide a quick and reliable measurement of moisture. Producers can do this by using a specialized feed-drying oven, conventional laboratory oven, toaster oven, conventional oven or microwave oven. The microwave oven’s convenience and availability make it an effective tool to determine the moisture content of hay and haylage. When used properly, it will produce values within 5 percent of the moisture content in accepted research methods. This margin of error is less than what occurs when using most moisture testers and probes on the market. The average time a producer needs to determine moisture content is three to five minutes for dry forages such as hay and five to eight minutes for wet forages such as haylage or silage. Producers using a microwave oven can use the following procedure to estimate moisture content of forges at harvest: 1. Obtain two or more samples (3 to 5 pounds) from the windrow. Discard any large weeds. 2. Chop each sample into 2- to 3-inch-long pieces; mix thoroughly. Weigh accurately using a dietetic, gram or postage scale. Start with 100 to 300 grams of forage. This will be your wet weight. For the most efficient test, spread the forage evenly on a plate rather than in a pile. For 300 grams, a glass casserole dish will make stirring easier. Be sure to use a microwave-safe dish or paper plate. 3. Place an 8-ounce glass three-fourths full of water in the back corner of the microwave. Keep the water amount somewhat constant during microwave use. 4. If, for example, an alfalfa haylage sample is estimated to be between 50 percent and 75 percent moisture, place the sample in the microwave for four minutes. Remove the sample from the oven, weigh and record the weight. Stir the forage on the plate and place it back in the microwave for two minutes. As the forage sample begins to feel dry, reduce the microwaving time between weighings to one minute. Continue this procedure until the sample weight does not reduce more than 1 to 2 grams (2 grams is 0.07 ounce) from the previous weighing and/or the forage starts to char. If analyzing a hay sample that you estimate at 35 percent moisture or less, microwave it for two minutes at the beginning, then return it to the oven for another half minute per drying period. 5. The dry weight is the last weight you record when the sample weight has not decreased more than 1 to 2 grams from the previous weighing. 6. To calculate percent of moisture content, use the following equation:
Once you are familiar with using the microwave for drying forage, you will be able to obtain a final dry weight the first or second time you dry in the oven. The initial drying never should last more than four minutes for wet or two minutes for dry samples. Anytime severe charring results, redo the procedure. Be sure to check several samples from the field because moisture may vary slightly between samples. Here is an example of dry-matter determination using 300 grams of wet forage:
Here is a record of the weights of the plate and sample after heating (total heating time in this example is 14 minutes):
The plate plus the final sample weight is 219 grams. Subtract the weight of the plate (54 grams). The net final sample weight is 165 grams. The dry matter percent is [(165 ÷ 300) x 100] = 55 percent, and moisture percent is 100 - 55 = 45 percent. Schroeder says the odors that the testing produces may not be desirable in the house, so use this method in an open area or barn. He also recommends you don’t use your good microwave oven. ### Source: J.W.
Schroeder, (701) 231-7663, jschroed@ndsuext.nodak.edu |
Market Advisor: |
|
North Dakota State University |
