Effect of Mixed Microbial Culture Treatment on the Nutritive Value of Coffee, Green Tea and Oolong Tea Residues and the Effect of the Fermented Residues on in Vitro Rumen Fermentation

Abstract

The aim of this study was to increase the nutritive value of coffee, green and oolong tea residues and assess if the fermented residues have the potential to mitigate enteric methane emissions. A mixed microbial culture (20g/kg) was added to each residue and the mixture incubated for 3 d at 35°C (anaerobically) and 2 weeks at 30°C (aerobically). Unfermented and fermented beverage residues were assayed for their saccharide and ethanol content. Four separate total mixed rations (TMR) were prepared using the three fermented beverage residues and hay (control). The fermented residues (2g/kg dry matter (DM)) were individually mixed with hay (3g/kg DM) and concentrate (5g/kg DM) and the in vitro rumen methane output was quantified during the 24h incubation period using the continuous gas quantification system. The fermented residues of coffee, oolong tea and green tea had higher concentrations of cellotriose, cellobiose and xylobiose than the corresponding unfermented residues. Ethanol concentration was higher in the fermented coffee and green tea residues than in their respective unfermented residues. The methane output (L CH4/24h) from the TMR containing fermented residues of coffee (0.118 L), oolong tea (0.127 L) and hay (control; 0.123 L) did not differ, but the methane output was lower for all compared to the TMR containing fermented green tea residue (0.141 L). The results suggest that fermented coffee, oolong tea and green tea residues are a potentially good source of protein and energy, and fermented residues of coffee caused a numerical decrease methane output.