Effects of green-synthesized CuO and ZnO nanoparticles on ruminal mitigation of methane emission to the enhancement of the cleaner environment

This study was carried out to determine the effects of adding CuO and ZnO nanoparticles (at levels of 0, 10, and 20 mg of CuO and ZnO nanoparticles in mL rumen fluid) on in vitro gas and methane production of alfalfa (Medicago sativa) hay. Green-synthesized CuO and ZnO nanoparticles were characterized using scanning electron microscope (SEM), Fourier transform infrared (FTIR), energy dispersive X-Ray spectroscopy (EDX), and atomic force microscopy (AFM) microscopes. The use of CuO and ZnO nanoparticles had significant effects on ruminal protozoa colonization, in vitro gas production, and mitigation of methane emission (P < 0.05). The use of CuO nanoparticles led to a decrease in the protozoa population, thus indirectly decreasing the ruminal fermentation. The CuO nanoparticle is not recommended biologically, but ZnO increased protozoa population and gas production; therefore, this nanoparticle could only exert beneficial effects on rumen fermentation and is recommended.