Fiber digestibility testing has come a long way as a tool to assess forage quality. For instance, lab assays that use 24- or 30-hour in vitro fermentation to measure the neutral detergent fiber digestibility of forages work just as well as the traditional 48-hour method. However, challenges still exist, says Dave Combs, professor of dairy science at the University of Wisconsin. For instance, techniques used to measure NDF digestibility are not standardized across forage-testing labs and inconsistency in test results often exist between labs, Combs said at the Midwest regional meeting of the American Dairy Science Association held in mid-March. Further improvements in testing methods are important because NDF digestibility is positively correlated with milk production. The higher the NDF digestibility of forages, “the higher the milk production potential,” Combs said.