Vol 6: No. 2
A Quick Guide to Understanding Forage Test Results
Laboratory testing of forages for nutrient content and digestion
characteristics is an important management step in the process of
formulating dairy rations. In recent years, there have been numerous
changes in forage analysis by commercial testing laboratories. These
changes are sometimes difficult to understand and minor philosophical
differences still exist within different dairy regions across the United
States. As a result modern forage test reports sometimes yield as many
questions as answers. For example, many laboratories are now testing
forages for NDF digestibility, but dairy producers or nutritionists may
not be familiar with normal averages or ranges in NDF digestibility for
forages grown in their area. For the most part, however, concentrations of
key nutrients within forages such as protein, energy, fiber, calcium, etc.
remain the basis for defining the quality of one forage over another.
Additional forage tests, such as NDF digestibility, lignin, starch etc,
that are now done routinely in commercial testing labs help to better
define the quality of forages.
Understanding Forage Tests - A Quick Guide
Presented in Table 1 is a simple scheme to aid dairy producers and nutritional consultants with understanding forage tests by defining forage nutrients into specific functional use categories. These categories are defined according to nutrients commonly used to: 1) predict dry matter intake, 2) estimate energy values, 3) direct use in ration formulation, 4) nutritional diagnostics, 5) supplementation strategies, 6) quality indexing, and 7) agronomic performance trials.
In addition to defining forage test parameters by functional use categories, dairy producers and nutrition consultants often request some guidelines as to what typical values are and what desired values should be. Using database information from Upper Midwest forage testing laboratories, we have attempted to define common ranges for forage test results and provide a general idea of desired ranges for milking and dry cows. Dairy producers and nutritionists from dairy production areas with different forage sources and (or) growing conditions may want to ask their regional forage testing laboratories to construct a similar quick guide.
Adapted from: Hoffman, P., and R. Shaver. 2004. Sorting through forage test results. Hoards Dairyman. Vol1149, No. 16:590.