Abstract:

The object of this study was to investigate the effect of purple maize anthocyanin extract on in vitro gas production and rumen fermentation in beef cattle. A completely randomized design was used. Levels of 0， 0.2%， 0.4%， 0.6%， and 0.8% purple maize anthocyanin extract were added to the substrate， and total gas production， gas production kinetic parameters， volatile fatty acid， methane production， cellulase activity， and nutrient degradation rate were measured. It was found that： 1） Total gas production after fermentation for 72 h tended to be reduced where anthocyanin was added， and gas production at 72 h for the 0.6% anthocyanin group was significantly lower （P<0.05） than that of the control group. 2） By contrast， gas production from the immediately soluble fraction tended to be higher with anthocyanin present and was significantly higher （P<0.05） in the 0.4% anthocyanin group than in the control group. The gas production rate constant decreased with increase in the purple maize anthocyanin extract supplemental level， and the control group was significantly higher （P<0.05） than the other four anthocyanin groups， and the curve defining the trend across anthocyanin levels had both linear and quadratic significant （P<0.05） terms. 3） The contents of acetic and butyric acid at 24 h decreased with increase in added anthocyanin， with significant （P<0.05） linear and quadratic terms for the fitted curve. Accordingly， the contents of acetic and butyric acids in the control group were significantly higher （P<0.05） than those of the 0.4%， 0.6%， and 0.8% anthocyanin groups. In contrast， the content of propionic acid increased with increase in supplemental purple maize anthocyanin extract， with both linear and quadratic terms of the fitted curve being significant （P<0.05）， and accordingly， the content of propionic acid in the control group was significantly lower （P<0.05） than other anthocyanin groups. The acetic：propionic acid ratio and methane production both decreased with increase in the level of anthocyanin extract and in both cases the fitted curve had significant （P<0.05） linear and quadratic terms. Accordingly， acetic：propionic acid ratio and methane production in the anthocyanin groups were significantly lower （P<0.05） than that of the control group. 4） At 12 h fermentation time， carboxymethyl cellulose and cellobiase were increased with increase in the supplemental anthocyanin extract level and both linear and quadratic terms were significant （P<0.05）. Accordingly carboxymethyl cellulose and cellobiase levels in the 0.8% anthocyanin group were significantly higher （P<0.05） than in the other four groups. Meanwhile， the values of xylanase in the 0.2%， 0.4%， and 0.6% anthocyanin groups were significantly higher （P<0.05） than those in the control group at 24 h fermentation time. 5） Both crude protein degradation rate and acid detergent fiber degradation rate increased with increase in supplemental anthocyanin extract level， and linear and quadratic terms of the fitted curves were significant （P<0.05） increasing. Accordingly， the crude protein degradation rate in the anthocyanin groups was significantly higher （P<0.05） than that of the control group. Taken together， purple maize anthocyanin extract had the ability to improve rumen fermentation mode， increase propionic acid， cellulase activity， and nutrient degradation rate， and decrease methane production of beef cattle. Under the conditions of this experiment， the optimal purple maize anthocyanin extract level was 0.4%.

Key words: anthocyanins, in vitro gas production, rumen fermentation, beef cattle