In Vitro Fermentation Characteristics of Seven Commonly Used Dairy Roughages With Relatively High and Low Nutritive Values

Roughage constitutes a fundamental component of dairy cow diets; it promotes rumen health and supports optimal animal productivity. This study applied an ANKOM gas production system to assess the in vitro fermentation characteristics of seven widely used dairy roughages (barley hay, corn silage, lucerne hay, oaten hay, ryegrass hay, timothy hay and wheaten hay) classified into relatively high and low nutritive value groups. Roughage samples representing high and low nutritive values were selected based on the upper and lower quartiles of the feed quality database. The results showed that high-nutritive value oaten hay exhibited higher dry matter (DM) digestibility (0.50 vs. 0.24–0.43 g/g DM, p < 0.05), total gas production (87.5 vs. 15.3–81.0 mL/g DM) and total volatile fatty acid (63.2 vs. 39.3–62.5 mM) than other roughages. High-nutritive value barley hay and oaten hay both exhibited higher methane production (7.58 and 7.77 mL/g DM, respectively) compared to other roughages (0.44–4.76 mL/g DM). Similarly, high-nutritive value barley hay (40.23 mg/100 mL) and lucerne hay (40.76 mg/100 mL) exhibited higher ammonia nitrogen (12.16–31.99 mg/mL) than other roughages. High-nutritive value oaten and barley hay promoted superior fermentation performance but also led to greater methane emissions, while barley and lucerne hay increased nitrogen release. These results underscore the need to balance productivity with environmental impacts when selecting roughages for dairy systems.