Nutrient Composition and Protein Extractability of Oat Forage Harvested at Different Maturity Stages as Compared to Grain

Two oat varieties (CDC Dancer and Lamont) were grown in fields. Plants were harvested at three key stages- seedling (Forage 1), mid-season (Forage 2), and full grain maturity. The mature plants were separated into stover (Forage 3) and Grain. There were differential changes among measured attributes during growth. From seeds to Forage 1, crude protein (CP) and ash contents increased several fold, beta-glucan decreased, starch disappeared, and oil content remained unchanged for both oat varieties examined. As plants grew, CP, ash, oil and beta-glucan decreased, but other carbohydrates increased significantly. The CP content in Forage 1 was 5–fold higher than Forage 3 and 2-fold higher than Grain. Most macro and micro-minerals in forage followed the same changing pattern as ash. Amino acid composition of forage differed significantly from that of Grain. When subjected to aqueous media with a wide range of pH, forage harvested at each stage as well as grain all had their unique protein extractability curves. For forage, the peak value (the maximum extraction) decreased with maturity. Yet, as observed for both varieties, Forage 1 had a peak value half of that from Grain. In conclusion, based on the results from this study, nutrient composition in oat forages harvested at an early stage can be comparable or even superior to oat grains but low protein extractability limits oat forage use as an alternative protein source for non-ruminants.