Chemical and phytochemical composition, in vitro ruminal fermentation, methane production, and nutrient degradability of fresh and ensiled Paulownia hybrid leaves

•Paulownia leaves are rich in crude protein and essential amino acids.•Paulownia leaves and its silage reduce rumen methanogen counts.•Paulownia leaves and its silage mitigate methane production.•Paulownia leaves and its silage improves rumen fermentation characteristic. Paulownia is a genus of fast-growing trees that generate a huge mass of leaves, which can be utilized as a feed resource for ruminants. In the present study, the chemical and phytochemical composition, in vitro ruminal fermentation and methane production, and nutrient degradability of fresh Paulownia hybrid leaves (PL) and its silage (PLS) were investigated. The crude protein content of PL and PLS ranged from 132 to 199 g/kg dry matter, which was comparable to alfalfa silage (AS). Ensiling of PL increased the amount of both phenolic acids and flavonoids. The amino acid content increased, and total saturated fatty acid concentration tended to increase in PLS compared with PL. In the in vitro study with the ruminal fluid (batch culture), PL and PLS decreased pH (P