Oat (Avena sativa) is an underutilized cereal grain in Ethiopia from the Poaceae grass family. This study aimed to investigate the proximate, mineral, and anti-nutrient composition of three landrace varieties commonly used in certain districts of the country and compare them with two improved varieties of oats in Ethiopia. The proximate and mineral composition was determined using the Association of Official Analytical Chemists (AOAC) standard methods. Phytate and tannin contents were determined using the spectroscopic method, and oxalate was analyzed using HPLC. The bioavailability of minerals was also estimated. Results showed significant (p < 0.05) differences in proximate, mineral, and anti-nutrient compositions among studied varieties. The moisture, crude protein, crude fat, crude fiber, ash, and total carbohydrate contents were in the range between 8.5-9.8, 11.9-15.8, 6.7-10.3, 2.1-3.5, 1.2-1.3, and 72.6-74.3 g/100 g DM, respectively. Iron, copper, zinc, magnesium, calcium, and potassium contents were 2.5-3.0, 0.2-0.4, 1.6-2.0, 62.4-89.1, 44.0-102.7, and 241.7-258.3 mg/100 g DM, respectively. The oxalate, tannin, and phytate contents ranged from 28.2-71.4, 38.8-51.5, and 269.6-293.0 mg/100 g DM, respectively. Except for a few varieties of oats, the molar ratios were below the critical values. Results showed that both the landraces and improved varieties studied are an excellent source of valuable nutrients. Thus, the production and utilization of this crop in a few geographical locations and communities should be further encouraged in the rest areas of the country to benefit from this underutilized but nutritious crop.
