Effect of fungal treatments of fibrous agricultural by-products on chemical composition and in vitro rumen fermentation and methane production

► A fungus–substrate interaction was observed on nutritional values of fibrous by-products. ► Nutritional improvement by some fungi linearly increased with the level of lignin in substrates. ► Pleurotus ostreatus is an effective lignin degrader but could not improve the nutritive value of fibrous by-products. ► Treatment of oil palm fronds with Ceriporiopsis subvermispora reduced methane emission from rumen fermentation. Maize stover, rice straw, oil palm fronds and sugarcane bagasse were treated with the white-rot fungi Ceriporiopsis subvermispora, Lentinula edodes, Pleurotus eryngii, or Pleurotus ostreatus at 24°C for 0–6weeks. The fungi increased total gas production from oil palm fronds by 68–132%, but none of the fungi improved the in vitro rumen fermentability of maize stover. C. subvermispora and L. edodes increased total gas production of sugarcane bagasse by 65–71%, but P. eryngii and P. ostreatus decreased it by 22–50%. There was a linear relationship (P