RELATIVE FEED VALUE

Relative Feed Value or "R.F.V." is a new term for many of us, and there are a lot of questions about it, as with anything new. Many hay buyers want to know the R.F.V. before buying hay. Once the R.F.V. is given, it is probably too low (according to him), so producers want to know how to improve the R.F.V.   

Relative Feed Value is nothing magical nor really new. For decades animal nutritionists have been searching for ways to measure the feeding value of hay. R.F.V. may seem a little more complicated than other measures of hay quality, but that is just because it is a new way to express the value.   

R.F.V. is a single value (or index) to estimate forage quality. R.F.V. combines the estimates for forage "digestibility" and forage "intake" into a single number. R.F.V. is calculated from estimations of A.D.F. and N.D.F.   

A.D.F. (Acid Detergent Fiber) and N.D.F. (Neutral Detergent Fiber) are determined by laboratory analysis of hay. The analysis can be by standard wet chemistry or by N.I.R.S. (faster and cheaper).   

The A.D.F. is used as an estimate of forage digestibility and N.D.F. is used to estimate forage intake by the animal.   

It should be noted that "Protein" or "Crude Protein" is not used in the calculation of R.F.V. Also, physical factors such as color, stem fineness, or leafiness are not used in the calculation of R.F.V. Consequently, it is possible for hay to be "pretty" and have a low R.F.V. High protein hay may sometimes have a low R.F.V. However, in general, hay that is high in protein also has high R.F.V. and usually looks good.   

The keys to improving Relative Feed Value are the same as the Keys to good alfalfa production --   

Maintain Healthy Alfalfa by providing good drainage, fertilize according to soil analysis, use adapted varieties, and reduce weeds.   

Early Harvest is essential for high R.F.V. Delaying a few days can reduce R.F.V. and Protein drastically.   

Keep All Leaves in the Bale because leaves make high quality; whereas, stems make most of the yield.   

High Relative Feed Value (above 150) is most important when feeding alfalfa to high-producing dairy cattle because it is important for them to consume large quantities of easily digested hay. When the amount of hay is limited, such as when supplementing mother cows during winter, R.F.V. is much less important because the intake is limited by the amount provided to the animals.   

It should be noted that R.F.V. is not the only commonly reported forage quality factor that is calculated. A.D.F. is used to calculate Net Energy (for Maintenance, Lactation, and Gain) and T.D.N. It is also used along with Protein analysis to calculate "digestible protein". The Hay Quality Standards below indicate the generally accepted relationships among Grade, Crude Protein, R.F.V. and Maturity at harvest, as developed by the American Forage and Grassland Council.
 

 
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