Articles on forages, animals, and grazing systems
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Extension Forage Specialist
University of Kentucky
Phone: (859) 257-3358
Fax: (859) 323-1952
Testing your forages can be a useful tool to minimize feeding costs while maximizing animal production. Forage testing provides the nutritional value of pasture, hay, or silage. It is important to know the quality and nutrient content of feed to calculate an efficient feed ration and mineral supplementation program. Balancing rations based on these test results are necessary to promote animal health and production while keeping feeding costs to a minimum. Knowing the nutritional value of your forage will also ensure that you are getting the right price for your hay when marketed.
Proper sampling and handling of forage is essential for accurate results. When sampling pastures, each paddock should be sampled and tested separately. It is beneficial to take separate samples within a single pasture if there is large variation in forage species or previous fertilizer applications within the pasture. It is suggested that 10-15 small samples be taken at random from a paddock under 40 acres. More samples should be taken in paddocks exceeding 40 acres. Samples need to be representative of the whole area and need to represent what will be grazed. Cut or tear forage at the approximate grazing height and avoid weeds that will be refused by livestock. Samples need to be handled properly between being removed from field and being delivered to forage testing laboratory. Samples can be taken directly to lab or mailed in. Put samples in a plastic bag on ice as soon as possible. Sample should be delivered to laboratory frozen or on ice. It is also an option to dry them in a paper bag but this is not the recommended procedure as they may mold if not properly dried.
Testing hay is beneficial whether you plan to feed it to your own livestock or sell it. Knowing the quality of hay can increase selling price and/or be used to create a more accurate winter feeding ration. When sampling hay, it is important that, individual cuttings, fields, and hay types (a lot) are sampled and tested separately. For most accurate results, test hay as soon as possible before feeding or marketing. A high quality coring device should be used to collect a minimum of 20 cores from each lot. Probe to a depth of 12-24” and take cores from butt ends of random bales or core towards the center of round bales from the edges not the flat end. It is important that samples are representative of the entire lot of hay. Do not choose bales based on whether they seem to be of low or high quality. Up to half of the material from each lot should be tested as soon as possible after the sample is collected. Keep the sample cool and dry after sampling.
Many different forage testing laboratories are available for testing your forages. It is recommended that you choose a lab that has been certified through the National Forage Testing Association (NFTA). Certified labs must meet the requirements of NFTA which includes accurately measuring check samples sent to them by NFTA. The Kentucky Department of Agriculture (KDA) meets these requirements and is one option for quality hay testing. KDA charges $10.00 per lot and an employee can assist with taking samples. A list of NFTA certified forages testing labs can be found at http://www.foragetesting.org/files/2012/2012_Certified_Labs.pdf.
Once you have correctly sampled your forages and received the results, interpreting results is a common area where mistakes are made. The majority of reports will include moisture, dry matter (DM), crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) values. Mathematical equations are used to calculate the relative feed value (RFV), total digestible nutrients (TDN), and net energy (NE) for lactation, maintenance, and gain. Crude protein is the percent of true protein and non-protein nitrogen. This number is used to decipher the forage’s ability to meet the protein needs of your livestock. This value is extremely useful when developing a ration because protein deficiencies lower forage digestibility and intakes. ADF value is the amount of indigestible plant material present. A low ADF value means a higher digestibility, energy value, and forage quality. NDF relates to intake. A low NDF value will allow livestock to consume more. The RFV is calculated using the ADF and NDF values to determine dry matter intake and digestible dry matter. Higher quality forages will have a higher RFV. Energy is the nutrient that is generally first limiting especially in high performance cattle. The net energy (NE) values show concentration of the megacalories (mcal) in the forage and is calculated for maintenance, growth, and milk production. It is important to use the correct NE for your livestock’s need. TDN is the percent of digestible material present and also represents the amount of available energy. Reports include results on an “as-fed basis” and “dry matter basis.” The dry matter basis reports the concentration of a given nutrient when all the water is removed from the forage while the as-fed column reports nutrient concentrations of the forage as it was received to the lab. Water dilutes the concentrations of nutrients and as-fed values will be lower than those in the dry matter column.
Contact your county extension agent for assistance with sampling, interpreting results, and/or designing winter feed rations. For more information on how to interpret forage quality reports see http://www.uky.edu/Ag/AnimalSciences/pubs/id101.pdf.