Oklahoma Alfalfa
Oklahoma Cooperative Extension Service
Oklahoma Agricultural Experiment Station

RELATIVE FEEDING VALUE (RFV), 
AN INDICATOR OF HAY QUALITY   

The best measure of the quality of a forage is animal productivity. Animal productivity is in turn affected by the intake and digestibility of the forage as well as the efficiency of utilization of the absorbed nutrients.   

Neutral-detergent-fiber (NDF) provides an estimate of forage intake, while acid-detergent-fiber (ADF) estimates forage digestibility. Crude protein is always of importance in cattle rations, especially dairy rations, because it is usually the highest priced nutrient.   

The principal forage analysis values used in ration formulations are: (1) protein; (2) ADF; and (3) NDF. These values are also used by hay buyers and sellers to estimate the feeding value of forages. Both buyers and sellers continue to look for a common means of estimating the quality of hay in terms of its value as a feed for livestock. RFV represents a single value that relates to the estimated quality of a forage as a livestock feed. The RFV has been used in certain hay areas of the U.S. more than in others.   

Relative Feed Value is a calculated value, utilizing ADF and NDF. It does not take into consideration the protein content of the forage. Protein level of the forage must be evaluated separately. Before RFV can be calculated, ADF and NDF must be used to calculate two other values. These values are Digestible Dry Matter and Dry Matter Intake. While different laboratories may use slightly different formulas to calculate these factors, the final estimated value are very similar.   

A forage with 28% ADF and 38% NDF will have about 67.1% Digestible Dry Matter and Dry Matter Intake of 3.15% of body weight. From this, the RFV equals 164.   

To establish a base-point that will enable one to better determine just where an RFV rates on the quality scale, it can be noted that an ADF value of 41% and an NDF of 53% would relate to a RFV of 100. The higher the RFV is above 100, the higher quality of the forage. For example, alfalfa hay cut at full bloom would be expected to have an RFV of 100. The following examples show the general relationships among protein, ADF, NDF, and RFV. 
 

   
Remember, RFV has no specific nutritional meaning and should be used only as an index of the relative value of a forage. If buyers are interested in knowing the RFV of your forage then it may be of value to you as a marketing tool. Be sure to quote the protein value of your hay also as it is not included in the calculation of RFV.  

For additional information:  
Forage Quality Interpretations. OSU Extension Facts F-2117   

Hay Judging. OSU Extension Facts F-2588   

Collecting Forage Samples for Analysis. OSU Extension Facts F-2589 
 
Minimizing Losses in Hay Storage and Feeding

Understanding Forage Quality