Forty-four alfalfa hays from different cuttings, maturities, and locations were fed to sheep in a digestion study. Subsamples of the hays along with corresponding fecal samples were ground and analyzed for dry matter, (DM), organic matter (OM), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and permanganate lignin. In vivo digestibility (IVDMD) were also determined fro each hay. The hay and fecal samples were scanned with a near infrared reflectance spectrophotometer. Chemical and digestible data for each hay and fecal sample were entered into the computer and separate multiple regression equations developed. Fifteen other alfalfa hays with known chemical and digestible data were used to test the alfalfa equation. Standard errors of analysis (%) and corresponding r2s were: 3.55 and 0.81, 0.23 and 0.99, 2.44 and 0.94, 0.85 and 0.98, 1.33 and 0.96, 1.13 and 0.96, 1.13 and 0.80 for DDM, CP, IVDMD, ADF, NDF, and lignin, respectively. Thirty fecal samples with known chemical data were used to test the fecal equation. Standard errors of analysis and corresponding r2s were: 0.13 and 0.96, 0.41 and 0.93, 0.87 and 0.96, 1.79 and 0.90, 2.10 and 0.91, 1.46 and 0.90 for DM, OM, CP, ADF, NDF and lignin, respectively. Using the spectral information from fecal samples and the chemical composition of alfalfa samples to analyze other alfalfa samples was examined. Twelve other alfalfa hays with known chemical and digestible data were used to test the fecal equation. Standard errors of analysis (%) and corresponding r2s were: 4.05 and 0.01, 1.54 and 0.48, 1.63 and 0.71, 13.16 and 0.55, 1.43 and 0.35, 6.52 and 0.13, 4.30 and 0.63, 2.36 and 0.09, 5.75 and 0.49 for DM, OM, CP, IVDMD, ash, NDF, ADF, lignin, and DDM respectively. Hay fecal samples were sieved to study the utility of using sieving as a procedure to support chemical data in predicting DDM. Use of sieving (alfalfa and fecal) and chemical data (other than IVDMD) increased the precision of predicting DDM (R2 = 0.76), over using IVDMD and ash concentrations to predict DDM (R2 = 0.66).