Effects of citrus flavonoid extracts on rumen fermentation parameters

The aim of this thesis study was to determine the effect of citrus extract (2.5%; 5%) addition to rumen contents on pH, ammonia (NH3-N), volatile fatty acids (VFA), in vitro gas production, fermentation kinetics and in vitro dry matter neutral detergent fibre digestibility (IVNDFDDM), true digestibility (IVTDDM) and organic matter digestibility (IVOMDDM). In the study, forage-weighted TMR (TMRkaba; 30g alfalfa, 30g maize silage, 15g maize, 15g barley, 15g wheat; forage/concentrate ratio 60/40) and concentrate-weighted TMR (TMRkon: 20g alfalfa, 20g maize silage, 20g maize, 20g barley, 20g wheat; forage/concentrate ratio 40/60) were prepared and used as substrate source in vitro. In the study, groups were formed as a control group without any additive, experimental groups in which two different doses (2.5% and 5%) of a commercial (Elito® Smart chemistry; water extract) citrus flavonoid extract were added and a positive control group in which monensin (Sigma Chemical Co.), one of the ionophoric antibiotics, was added at a level of 30 ppm (2 TMR x 4 groups).The rumen fluid required to create the in vitro rumen environment was obtained from two rumen cannulated Holstein cows with a live weight of approximately 650 kg. In the study, the pH values of the rumen fluid samples taken from the in vitro environment at 6, 12 and 24 hours were not statistically different (p>0.05) between the TMR groups, while the 24-hour pH (p<0.006) and NH3-N (p<0.001) values of the groups to which citrus extract (especially 5%) was added were lower than the other groups. At 6, 12 and 24 h, there was no interaction between TMR type and extract and monensin groups for ammonia (NH3-N) values and total in vitro gas production of rumen fluid samples (p>0.05). Regardless of TMR type, more total volatile fatty acids (TVFA; p<0.024) and in vitro gas production (p<0.001) and less methane production (p<0.022) were observed in the extract-supplemented groups. It was found that different TMR cultivars and extracts and monensin had no effect on CO2 production (p>0.05). Maximum gas production values (VF, mL) were lowest in the monensin supplemented groups (p<0.001). Microbial biomass production (MBP24, mg/g) was higher in all extract supplemented groups and lower in monensin supplemented groups (p<0.001). Compared to the control group, the %IVTDDM value decreased in the citrus extract and monensin added groups (p<0.001). When the results of the study are evaluated, it is seen that citrus flavonoids may be an alternative to ionophoric antibiotics. It is considered that these results from in vitro studies should be supported by more detailed in vivo studies using different extraction methods and varying doses. Keywords: Rumen, citrus extract, flavonoids, in vitro, fermentation kinetics