A:   In years past we have used a forage testing system that measured two different types of fiber called NDF and ADF. We used NDF to estimate how much of the hay cows would eat and we used ADF to estimate how much energy they would get from that hay. Then we combined those values to give an overall estimate of forage quality that we called RFV, which stands for relative feed value.

We’ve known that ADF is not as accurate as we would like for estimating energy. Grass hay and corn silage in particular often had poor energy estimates using ADF. The problem was that we had to assume that all fiber had the same digestibility. We knew that was not true, but unfortunately, there was nothing available at an affordable cost that was any better. But now there is!

New, low-cost tests finally have been developed that do a very good job of measuring digestible NDF. Animal nutritionists and forage scientists have worked together with these tests to also revise the intake and energy estimates so that results from these tests will much more accurately predict how animals will truly perform. Likewise, a new overall estimate of forage quality was developed, which is called RFQ and stands for relative forage quality.

So when you test forages in the future, look for labs that offer relative forage quality. Your numbers will be more accurate.