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Independent digestion trials were conducted with three immature grasses, mature grass hay, and alfalfa hay to compare n-alkane with indigestible ADF (IADF) as internal markers to predict in vivo dry matter digestibility (DMD). Forage DMD estimated with n-alkane ratios were lower than in vivo DMD. N-alkanes predicted higher DMD than IADF for alfalfa hay and two of the immature grasses. Comparison of freeze-drying and oven-drying on fecal n-alkane concentrations showed oven drying reduced amounts of n-alkane extracted for alfalfa hay but had no effect on grass hay. Although fecal recovery of markers was incomplete, more n-alkane was recovered than IADF.