Valorizing rice husk bio-waste into nutrient-rich feed ingredient through microbial fermentation

Rice residue burning contributes significantly to global warming through greenhouse gas emissions that threaten ecosystems. Converting rice residues into animal feed offers a sustainable strategy to mitigate emissions and support a circular economy. In this study, rice husk (RH) was bioconverted into nutrient-rich animal feed using ensiling with lactic acid bacteria (Levilactobacillus brevis –Lb and Pediococcus pentosaceus – PP) alone or combined with cellulase enzyme (C). The effects of fermented RH on methane production and ruminal fluid metabolites were also evaluated. Both LAB and LAB + C treatments significantly reduced pH of RH, indicating effective fermentation. LAB inoculation increased lactic acid (LA) and reduced acetic and butyric acid levels. The highest LA production was observed in RH treated with PP + C (2.37 ± 0.21 DM %) or Lb + C (2.83 ± 0.06 DM %), compared to PP alone (0.70 ± 0.09 DM %) or Lb alone (1.16 ± 0.11 DM %). LAB + C treatment markedly decreased acid detergent fiber (ADF), neutral detergent fiber (NDF), cellulose, and lignin contents. Microbial community analysis showed that LAB + C treatments shifted the microbial composition toward a higher abundance of Pediococcus and Levilactobacillus, accompanied by reduced microbial diversity. Fermented RH exhibited improved digestibility, increased propionate concentrations, and significantly reduced methane production (CH4 mL/d DM and CH4 mL/d NDF). Additionally, total volatile fatty acids (VFA), butyrate, and the acetate-to-propionate ratio differed significantly among treatments. Overall, the bioconversion of RH into animal feed offers a sustainable, cost-effective approach to reducing environmental pollution.