RELA nONSHIPS AMONG TESTING RESULTS OF CALIFORNIA ALF ALF A HA y SAMPLES

A group of231 alfalfa hay sample results received by a commercial lab over 4 years of hay testing in the San Joaquin Valley of California were examined for the relationship between various lab results. ADF2 and NDF were linearly related in this data set (90% of the variation in NDF is explained by the ADF value = R2). There was a very poor relationship between ADF value and CP (R 2 of 26%), which confirms that no direct inference about protein can be reliably derived from the fiber value. RFV is an index for rating hays and is calculated ADF and NDF lab results. and commonly used in midwestern states but not in California. ADF alone explained 95% of the variation in RFV, and NDF alone explained 99% of the variation in RFV. It is likely that with the mostly pure alfalfa hays grown in California, a single observation ofNDF ( or with slightly less confidence ADF) can adequately duplicate an evaluation of hay which uses RFV. RFV has the disadvantage of utilizing two separate analysis (ADF and NDF, each with its own range of error) for the calculation. The calculated RFV values from the California samples for each category indicate little agreement between CA standards (based on ADF) and the Midwestern RFV standard. If the RFV standards which are currently in place for midwestern states were adapted here in California, the categories of hay for each group would automatically increase approximately 1 full category in many cases, lowering the standards significantly. It is unlikely that market conditions in California would reflect these standards. Therefore, RFV is not recommended for use in California at this time. Table I. Relationship of Currently-used ADF Standards, NDF values at those ADF levels, and calculated RFV values. A B c D E F Category NDF (Average at given ADF) RFV (CA Samples ADF (Current Standards RFV (Midwestern Standards Currently Used) ADF Equivalent (from Midwest Standards) Supreme <27 <33.9 >186.2 >180 <27.8 Premium 27-29 34-36.2 .70.5-186 150-180 27.9-32.1 Good 29-32 36.3-39.6 150.4-170.5 125-150 32.2-36.7 Notes: Colwnn A=CA & National Hay Standard Categories~ B=ADF values for each category; C=NDF calculated at the given ADF (CA Data)~ D=RFV calculated from ADF & NDF for each categoy (CA data)~ E=RFV used in midwestern standards~ F=ADF equvalent value calculated for the given RFV values from the Midwest Standards, using the relationship found in CA hays. These (F) indicate the ADF values which would be used if the midwestern RFV standards were adapted.IForage Specialist, Dept. of Agronomy and Range Science, University of Calfornia, Davis 95616, Published IN 28d1 California Alflafa Symposium, 3-4 December, 1998. Reno, NV. UC Davis. 2 Abbreviations: ADF = Acid Detergent Fiber, NDF=Neutral Detergent Fiber, mN=Total Digestible Nutrtients {calculated from ADF), CP=Crude Protein, RFV=Relative Feed Value.