Understand Your Forage Analysis

January 10, 2010 06:00 PM

By Sara Brown

Reading your forage analysis can give you a headache because there are so many different acronyms and values that you receive back. Here are a few areas to look at first:

• Acid (ADF) and Neutral Detergent Fiber (NDF): "Acid detergent fiber (ADF) and neutral detergent fiber (NDF) measure the cell wall plant components of the grass or other forage in the sample,” says Shawn Deering, a University of Missouri Extension livestock specialist in Gentry County. 

NDF measures hemicellulose, cellulose, and lignin, which represent the fibrous bulk of forage. These components are called cell wall or structural carbohydrates. They give the plant rigidity, enabling it to support itself as it grows. Cellulose and hemicellulose can be partially broken down by microbes in the rumen to provide energy to the animal. 

NDF is negatively correlated with intake; a high percent NDF reduces forage intake. A normal range is 30% to 60%on a dry matter basis. 

ADF is a measure of cellulose and lignin. ADF is negatively correlated with overall digestibility; high ADF feed is less digestible. A normal range is 25% to 45% on a dry matter basis. 

• Total digestible nutrients (TDN): A measure of energy. "Ball park rule of thumb is if you can have hay that is 8% protein, with 55% to 54% total digestible nutrients (TDN), you are going to meet the needs and requirements of your cow herd most of the time,” Deering says.

•  Net Energy System: "The net energy system is similar to TDN, but we break energy down into different components—net energy for gain, net energy for maintenance and net energy for lactation,” Deering says. These values can guide producers to do a more precise job of determining how much energy is there to just maintain the animal, how much energy is left after that for the animal to gain and grow and how much energy is left to help the animal lactate and develop milk.”

•  Relative feed value (RFV): RFV is an index where a value of 100 indicates the sample has the same energy component of full-bloom alfalfa hay. "Many people who are in the business of hay selling and trading will use that value as part of a marketing tool,” Deering adds.

• Relative forage quality (RFQ): RFQ takes RFV another step, adding protein into the component. RFV is a measure of energy while RFQ adds crude protein into the equation. It is the represented with the same 100-value scale with a full bloom-alfalfa average.

• Minerals: "Some particular tests show a lot of mineral values,” Deering says. "The two beef producers are most concerned about is calcium and phosphorus.”  

Chris Derks, a beef producer in northwest Missouri also uses his forage analysis to test for nitrate levels. Derks's brother custom applies manure from his hog production facility on the ground Derks uses for forage, so he keeps a close eye on the nutritional value of the end product. 

Derks also works with his feed and mineral company nutritionist to sort out the different values and to calculate rations. 

"There is a lot of information in forage analysis, sometimes more than we sometimes need, but if you understand those basic values it will go a long way to serving the needs of your herd and making the most of your forage resources,” Deering says.

Testing distillers' grains. Producers should also be proactive to test distillers' grains. The nutrition content of the feedstuff can vary according to plant efficiency and the type of grain used (stored versus freshly harvested). 

"When you send dry distillers grain to the lab, the resulting energy value will fool some people to misbalance their ration because university trials have shown dried distillers' grains (DDGs) to have a greater energy value than corn,” says Ki Fanning, nutritionist with Great Plains Livestock Consulting in Eagle, Neb. "If you over feed distillers' grains, the extra fat content will start to counteract digestion by killing the fiber digesting microorganisms in the rumen—exactly the opposite of what producers want.”

"The fat level in dry distiller grains contains a lot of energy—fat contains nearly two and a half times that of corn,” Fanning says. "Start with a balanced ration, then watch body condition score of the animals and make adjustments as needed.”

Another advantage producers should notice when using DDGs is a change in mineral needs. Distillers' grains often contain an increased amount of phosphorus. "If they are feeding 1 lb. of DDGs per day or 2 lb. three times a week, a producer may be able to feed a mineral without phosphorus, which is a high-priced additive. That can save producers a lot of money on their range mineral cost.”

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