Abstract: This research evaluated seven oat varieties (Longyan No.1, Longyan No.3, Dinyou No.7, Bayou No.9, Bayou No.3, Baiyan No.2 and Jinyan No.17) for fresh biomass yield and fermentation quality, in order to identify the best oat variety for silage making. The experiment was conducted at Huajialing, Tongwei County in Gansu Province, and was harvested at the dough stage of grain fill. Fresh biomass, pH value and nutritional characteristics were measured; microbial counts and community analyses were undertaken by plate-culture. Fresh oat was then chopped to 2 cm lengths and ensiled. These silages were sampled 60 days after ensiling, with 3 replicates for each variety. It was found that: 1) There were significant differences (P<0.01) in fresh biomass and dry matter content between the varieties; Longyan No.3 had the highest fresh biomass (45257 kg·ha^-1), 28.13% higher than Dinyou No.7 (35320 kg·ha^-1). The dry matter content of the seven tested varieties ranged between 31.35% and 35.36%, with Longyan No.3 and Dinyou No.7 the highest. The bacterial counts on plants also significantly differed among the varieties (P<0.01). Lactic acid bacteria on Dinyou No.7 exceeded 105 cfu·g^-1 of fresh matter, higher than the others. 2) The nutrient contents also differed significantly between varieties (P<0.01) after 60 days ensiling. The crude protein contents of Longyan No.3 (10.12%) and Dinyou No.7 (11.09%) were significantly higher than the other varieties (P<0.01). The neutral detergent fiber content of Bayou No.3 (55.78%), Longyan No.3 (54.27%) and Dinyou No.7 (52.16%) were significantly higher than the other varieties (P<0.01). Longyan No.3 also had lower acid detergent fiber and the highest hemicellulose content. 3) The indexes of fermentation quality differed significantly among the varieties (P<0.01). Dinyou No.7 had the lowest pH value (4.13), followed by Longyan No.3 (4.20), and the highest pH value was in Jinyan No.17 (4.53). Silage from Dinyou No.7, Longyan No.3 and Bayou No.3 had higher content of lactic acid, lower total volatile fatty acids and lower ammonia nitrogen content, indicating a good fermentation quality. Bayou No.9 and Jinyan No.17 gave poorer fermentation quality performance. 4) The results of sensory evaluations were in accordance with V-Score evaluations. Longyan No.3 and Dinyou No.7 had the best fermentation quality, with level 1 sensory evaluation. Based on yield, nutritional composition and silage fermentation quality, Longyan No.3 was identified as the best among the tested varieties for planting for silage making in Huajialing and surrounding districts.

Key words: oat, varieties, silage, fermentation quality, lactic acid bacteria