Effects Of Dietary NSC/SC Ratio And Yucca Schidigera Extract On The Mechanism Of Rumen Methanogenesis In Vitro

The artificial rumen for incubation, enzyme activity analysis, and molecular biology techniques were used in current research, to interpret the manipulation mechanism of rumen methanogenesis, and the main proposal was to investigate the influence rule of yucca schidigera extract on the methanogenesis under different dietary NSC/SC ratio, and also tempt to supply some references for the methanogenesis regulation in the rumen. The paper comprised 3 parts described as follows.Trial 1, an In vitro culture was applied to analyze the development of fermentation, enzyme activity and methanogens, and try to explanation the mechanism of the effect of different NSC/SC on the rumen fermentation and methane production. the ratios of starch to cellulose in the cultrure substrate were designed as A(100:0),B(60:40),C(50:50),D(40:60),E(0:100). The results showed that the pH value decreased in advance and increased after, the NH3-N concentration decreased with the NSC/SC ratio decreasing; The acetic acid concentration fluctuated, and the concentration of propionic acid increased with the NSC/SC increasing; additionally, the butynic acid concentration was highest in group A, except A, increased from B to E. It was also observed that the ratio of acetate to propionate was upgraded with NSC/SC decreasing; accumulated gas and methane production all decreased with NSC/SC decreasing; whereas the ratio of methane production to accumulated gas increased with the NSC/SC decreasing, protozoa density tend to upgraded firstly and decreased after, and the ratio of protozoa mass to bacterial mass decreased gradually with NSC/SC decreasing. As the NSC/SC ratio decreasing, the intensity of F420 fluorescence decreased, and the total dehydrogenase activity decreased firstly and upgraded after, while the methane energy loss increased. The number of methanomicrobium and methanobrevibacter of group B was lower than that of the other groups, as for methanobrevibacter, whose number was highest in group A, and lowest in group D.Trial 2, the objectives of this part were to study the effect of yucca schidigera extract (YSE) on rumen fermentation parameters and CH4 production, and provided the eligible concentration of yucca schidigera for the following trails. The in vitro culture and in vitro gas production were conducted using corn+bean and straw (Concentrate-to-forage Ratio:3.5 to 6.5) as substrates, by adding 2 mg/g, 4 mg/g, 6 mg/g, 8 mg/g, 10mg/ g, 20mg/g, 30mg/g, 40mg/g, and 50mg/g yucca schidigera extract respectively. Results showed that eligible concentration of yucca schidigera extract in culture could stabilize the ruminal pH, and reduce the NH3-N concentration; the production of acetic acid, propanoic acid, butanoic acid and total VFA was reduced by adding yucca schidigera extract; In addition, yucca schidigera extract had an inhibitory effect on the microbial activity and the methane producing; when the concentration of yucca schidigera extract in the culture was below 8mg/g, the protozoon biomass fluctuation with yucca schidigera extract increasing, and total dehydrogenase activity increased, while the intensity of F420 fluorescence decreased with the increase of yucca schidigera extract. It was however that, when the concentration of yucca schidigera extract were higher than 10 mg/g, the total dehydrogenase activity decreased with YSE increasing, while the intensity of F420 fluorescence had a tendency of incline first and decline after; further observation revealed that there was little bacteriostasis activity, showing the high microbial activity, when the culture contained 40mg/g of YSE. Only in the culture containing 6 mg/g of YSE, most indexes such as, the total gas production, methane production and the protozoa density, and the ratio of methane to accumulated gas got their nadir. So, the eligible concentration of YSE was 6 mg/g.Trial 3 was conducted to determine the effect mechanism of YSE on the rumen fermentation and methanogenesis under partial concentrate (forage) feed. The experimental design was a 2×2 factorial design: one factor was the starch to cellulose ratio (60/40: partial concentrate, and 40/60: partial forage), the other was the concentration of YSE (6mg/g, and 10mg/g). The experimental result showed that the effect of methane inhibitors on the rumen methanogenesis was different according to the ratio of concentrate to forage. First with the partial concentrate feed, the inhibitory effect of 10 mg/g YSE was better than that of the 6 mg/g YSE, in rumen fermentation, methane production, the protozoa activity, and the activity of the methanomicrobium and methanobrevibacter; while under the partial forage condition, no effect was found in VFA by the addition of YSE, while microbial mass and NH3-N concentration of 6 mg/g YSE group was significant higher than that of the 10 mg/g YSE group, the other way round, the methane production, the intensity of F420 fluorescence, the total dehydrogenase activity, the number of methanomicrobium and methanobrevibacter of 6 mg/g YSE group was all lower than that of the 10 mg/g YSE group.