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June 24, 2004 Specialist Explains Rain’s Effect on Forage Quality Moisture conditions in North Dakota this year range from very dry to very wet, making it difficult to raise and/or harvest dairy quality forage, according to J.W. Schroeder, North Dakota State University Extension dairy specialist. “In the areas that have received rain, it arrived during alfalfa bailing or ensiling,” Schroeder says. “Rain that occurs between the time alfalfa is cut and harvested causes both yield and quality losses that reduce the value of the crop as an animal feed and a marketable commodity.” Weather induced losses are caused by:
Components of the plant that are very water-soluble are leached out of forage and lost when rain occurs. Most of these compounds are highly digestible by animals. They include readily available carbohydrates and soluble nitrogen, minerals and lipids. About one-half of the dry matter leached by rain is soluble carbohydrate. Given the same amount of total rainfall, a low intensity rain will result in more leaching of soluble compounds than a high intensity rain. “Excessive leaching of soluble carbohydrates can cause problems if forage is ensiled” Schroeder says. “It is these same carbohydrates that serve as a substrate for bacteria involved in the fermentation process.” In situations where carbohydrates are in low concentrations, silage additives that provide fermentable substrate might be needed to ensure proper fermentation. Schroeder notes that it is difficult to measure dry matter losses from increased plant respiration as a result of rainfall. Even without rain, respiration occurs in cut forage until the plant reaches near 30 percent moisture. Every time the forage is wetted by rain, respiration is either prolonged or begins again in cases where the cured forage was below 30 percent moisture. In either case, dry matter is lost. As forage moisture content declines, it is more prone to dry matter loss from rain. There is some disagreement in research literature regarding the amount of leaf loss that occurs in cut alfalfa as a direct result of rainfall. “However, experience and common sense tell us that rain damaged alfalfa is more predisposed to leaf shatter after it dries, and rainfall often means additional raking or tedding, causing more lost leaves,” Schroeder says. Most rainfall studies are in agreement that wetting of field-cured alfalfa has little impact on crude protein concentration. “Protein values alone will not be a good measure of forage quality in 2004,” according to Schroeder. “Depending on numerous factors previously discussed, the digestibility of rained-on hay can be extremely low and offer little nutritional value.” For more information about rain’s effect on forage quality, contact Schroeder at (701) 231-7663 or jw.schroeder@ndsu.nodak.edu. ### Source:
J.W. Schroeder, (701) 231-7663, jw.schroeder@ndsu.nodak.edu |
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North Dakota State University |
