In vitro ruminal fermentation, nutrient degradability, methane production, and microbial protein synthesis of a barley-based complex forage mixture compared to a barley monoculture when harvested at two maturities

This study evaluated the in vitro ruminal fermentation, nutrient degradability, methane production, and microbial protein synthesis of a barley-based complex forage mixture (COM) compared to a barley monoculture (MON), when harvested at two timepoints using the rumen simulation technique (RUSITEC). Each treatment was grown on four replicate paddocks. The COM was composed of 13 species, including barley, two millet varieties, ryegrass, three clover varieties, sunflower, hairy vetch, turnip, forage collard, phacelia, and chicory. Both forages were harvested when MON was at the soft dough stage (standing). One week later, crops were swathed, and samples were collected 4 weeks later (swathed). Samples were then incubated in the RUSITEC system to assess the effects of forage type and harvest timing. Dry matter, organic matter, crude protein, and water-soluble carbohydrates disappearance were greater for COM than MON but did not differ by harvest timing. Short-chain fatty acid production was not affected by forage type or harvest timing. Microbial protein production was greater for COM than MON, but total gas and methane production did not differ. Overall, COM forages had greater ruminal degradability, which stimulated microbial protein synthesis compared to MON, but forage type and harvest timing did not affect methane or total gas production.