A Quick Guide to Understanding Forage Test Results
by Patrick Hoffman and Randy Shaver
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.
To aid the understanding of the new forage testing schemes we have attempted to categorize forage tests according to their basic uses in dairy nutrition programming. Also summarized are test results for common forages of the North Central Region.
Understanding Forage Tests – A Quick Guide
Presented in Table 1 (click here to view or download here), 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.
Focus on Forage – Vol 6: No. 2
© University of Wisconsin Board of Regents, 2004
Pat Hoffman, Extension Dairy Scientist, Marshfield Agricultural Research Station
University of Wisconsin
Randy Shaver, Extension Dairy Scientist
University of Wisconsin – Madison