Mango Peel Fermented with Ethanol-Industry Yeast Waste and Urea Modulates In Vitro Rumen Fermentation, Nutrient Degradability, and Methane Concentration

Abstract

Simple Summary Two waste streams are generated in large volumes across tropical Asia: peel left over when mangoes are processed, and the spent yeast sludge discharged by ethanol distilleries. Mango peel still contains sugars, fibre, and protective plant compounds, but almost no protein, whereas yeast sludge is rich in protein, yet difficult to store and handle. In this study, the two wastes were mixed and fermented together in sealed bags for 14 days, which produced a dry, protein-enriched supplement. The supplement was tested in the laboratory with rumen fluid from cattle so that several inclusion levels could be screened before any animal feeding trial. It was added at four levels to two diets differing in the proportion of roughage to concentrate. Adding the fermented product increased gas production and fibre digestion, progressively reduced the number of rumen protozoa, and lowered the proportion of methane in the fermentation gas while leaving rumen acidity and ammonia unchanged. The clearest benefits occurred at about 4% of diet dry matter. Combining two discarded materials can therefore create a feed ingredient that supports rumen function while reducing the methane concentration of the fermentation gas.