Effects of quercetin onin vitro rumen fermentation and methane production of beef cattle

This study aimed to observe the effects of quercetin supplementation onin vitro rumen fermentation and methane production of beef cattle. A single-factor experimental design was used in this study, and the treatment groups included 0、0.5%, and 1% quercetin added to the substrate for in vitro fermentation, with no quercetin added used representing the control group. Rumen anaerobic fermentation was conducted at 39 ℃, and gas production (GP) at different times was recorded. The pH, ammonia nitrogen (NH₃-N) concentration, volatile fatty acid concentration (VFA), and methane production were determined after 48 h of fermentation. In addition, the dry matter disappearance (DMD) rate after 48 h of in vitro fermentation was determined by a two-step method. The following results were obtained: 1) After 48 h, gas and methane production of the 1% quercetin group was significantly lower than that of the control group (P < 0.05); pH did not show significant differences among the groups ( P > 0.05), and the NH ₃-N content in the 0.5% and 1% quercetin groups was significantly lower than that in the control group (P < 0.05). 2) the DMD rate was not significantly affected by quercetin ( P > 0.05); acetic acid, butyric acid, and total volatile fatty acids did not show significant differences between the 0.5% and 1% quercetin groups ( P > 0.05), while propionic acid in 1% quercetin group was significantly higher than that in the control group ( P < 0.05). In conclusion, the addition of quercetin to beef cattle diets may reduce gas production, decrease NH ₃-N contents, increase propionic acid contents, and decrease methane production by beef cattle, and 1% quercetin supplementation in beef cattle diets is most suitable.