Effect of Paulownia Leaves Extract Levels on In Vitro Ruminal Fermentation, Microbial Population, Methane Production, and Fatty Acid Biohydrogenation

Paulownia is a fast-growing tree that produces a huge mass of leaves as waste that can be
used as a feed source for ruminants. The previous study showed that phenolic compounds were the
most active biological substances in Paulownia leaves, which affected the ruminal parameters and
methane concentration. However, there are no scientific reports on the Paulownia leaves extract (PLE)
containing phenolic compounds for their mode of action in the rumen. Phenolics constituted the
main group of bioactive compounds in PLE (84.4 mg/g dry matter). PLE lowered the concentration
of ammonia, modulated the VFA profile in the ruminal fluid, and decreased methane production.
The PLE caused a significant reduction of in vitro dry matter degradability, reduced the number of
methanogens and protozoa, and affected selected bacteria populations. PLE had a promising effect
on the fatty acid profile in the ruminal fluid. Paulownia as a new dietary component or its extract as a
feed additive may be used to mitigate ruminal methanogenesis, resulting in environmental protection
and reducing ruminal biohydrogenation, improving milk and meat quality.