Validation of Brix for Predicting Sugar Concentrations of Alfalfa and Orchardgrass*

Objectives: The objective of this study was to evaluate the accuracy of Brix in predicting sugar concentrations in fresh alfalfa (ALF; Medicago sativa L.) and orchardgrass (OG; Dactylis glomerata L.) forages to be used as an inexpensive and rapid field-level assessment of relative energy in forages. Materials and Methods: In a 2-yr study, fresh forages samples from ALF and OG monoculture pastures in from May to September. Samples were immediately evaluated for Brix values with a hand-held digital refractometer, and the remaining biomass was frozen immediately with liquid N to halt cellular respiration. Samples were lyophilized and analyzed for individual sugars and wet Results and Discussion: Brix was positively correlated with total and individual sugars in ALF during late spring and late summer (0.53-0.93), but correlations were nonexistent or negative in mid-summer. However, Brix values did not correlate with any notable sugar parameters in OG beyond the first sampling date. These findings were attributed to greater fibrous fraction contamination, compared with horticultural crops, and changes in seasonal growth of ALF and OG. Implications and Applications: Brix values did not and nutritive values of fresh forages.