Coring Medium Rectangular Bales for Forage Analysis

Mike Rankin
Crops and Soils Agent
University of Wisconsin - Extension

        It's becoming almost the "norm" for hay to be packaged in medium rectangular bales weighing between 700 and 1000 pounds.  It is often these type of bales that now dominate the quality tested hay auction scene.  Buyers, sellers, and users of these hay packages often desire to sample the bales for a forage analysis test.  The question then becomes "How many cores are needed to obtain an ACCURATE assessment of forage quality?"

        Researchers at the University of Minnesota recently reported a study where they intensively sampled all bales (at least 6 cores per bale) in various hay lots to determine the actual forage quality and compared the results to those obtained with a less intensive sampling protocol.  One of the lots was an entire truckload of 55 bales.  In addition, several bales were cored 54 times each to develop a grid analysis and determine if core location within the bale influenced test results (as is the case with small square bales).  Bales were cored with a 14-inch long hay probe with a ¾" diameter.

Research conclusions

• Unlike small square bales, there was no consistent pattern of leaf and stem packing within the bales.  This means you can take samples from any point on a medium rectangular bale.

• It is most efficient to take one sample per bale.

• When sampling an entire lot of hay, core at least 12 bales (each sampled once) to get crude protein (CP) results within 1.2 of the true CP percentage.  At least 7 bales (each sampled once) need to be cored to get Relative Feed Value (RFV) within 8 points of the true RFV.  Sampling more bales than this may not give you more accurate results because of the error inherent in laboratory analysis.