不同植物精油对体外瘤胃发酵及甲烷产量影响的比较研究

在底物精粗比为6∶4的条件下,在底物中添加不同剂量使发酵液中植物精油的浓度分别为0(对照)、50、100、200和400 mg/L]的丁子香酚、D-柠烯、茴香脑、肉桂醛、百里香酚或香芹酚,通过体外产气法比较研究不同植物精油对体外瘤胃发酵和甲烷(CH4)产量的影响。每种植物精油的每个剂量设3个重复。体外模拟瘤胃发酵培养24 h,测定产气量和气体中的CH4含量以及发酵液的p H、挥发性脂肪酸(VFA)和氨态氮(NH3-N)浓度。结果表明:1)除百里香酚外,添加各种植物精油对体外发酵液p H均无显著影响(P0.05)。2)添加丁子香酚、D-柠烯、茴香脑和肉桂醛对体外发酵液总VFA浓度没有显著影响(P0.05),但总VFA浓度随百里香酚和香芹酚浓度的增加呈二次曲线变化(PQ0.01)。与对照组相比,添加400 mg/L百里香酚和香芹酚显著降低体外发酵液总VFA浓度(P0.01)。D-柠烯、茴香脑、百里香酚和香芹酚的添加改变了各VFA占总VFA的摩尔百分比。与对照组相比,添加50 mg/L D-柠烯和茴香脑使乙酸比例显著增加(P0.05),丙酸比例显著降低(P0.05);而添加400 mg/L D-柠烯和茴香脑则使乙酸比例显著下降(P0.05),丙酸和丁酸比例显著上升(P0.05)。百里香酚和香芹酚的添加对乙酸比例没有产生显著影响(P0.05),与对照组相比,400 mg/L百里香酚和香芹酚使丙酸比例显著下降(P0.05)。3)添加茴香脑、百里香酚和香芹酚显著影响体外发酵液NH3-N浓度(P0.05),与对照组相比,400 mg/L百里香酚和香芹酚显著降低NH3-N浓度(P0.05)。4)添加D-柠烯、茴香脑、肉桂醛对体外发酵24 h产气量没有显著影响(P0.05)。与对照组相比,各浓度的百里香酚和香芹酚均显著降低体外发酵24 h产气量(P0.05),且产气量随百里香酚和香芹酚浓度的增加呈二次曲线变化(PQ0.01)。5)添加D-柠烯、茴香脑和肉桂醛对体外发酵24 h CH4产量没有显著影响(P0.05)。与对照组相比,50和100 mg/L的丁子香酚显著增加体外发酵24 h CH4产量(P0.05),而400 mg/L的百里香酚和香芹酚体外发酵24 h CH4产量分别降低84.7%(P0.05)和73.9%(P0.05)。综合以上试验结果可知,不同植物精油对体外瘤胃发酵和CH4产量的影响结果不同,且与添加剂量有关。其中,低剂量的百里香酚和香芹酚促进体外瘤胃发酵,而高剂量的百里香酚和香芹酚抑制体外瘤胃发酵且显著降低24 h CH4产量。

A Comparative Study: Effects of Different Plant Essential Oils on Rumen Fermentation and Methane Production in Vitro

In this experiment, the cultivation substrate was consisted of concentrate to forage ratio with 60∶40, and adding different doses 0 (control), 50, 100, 100 and 200 mg/L fermentation liquid concentration, respectively] of plant essential oils (EOs) including eugenol, D-limonene, anethole, cinnamaldehyde, thyme and carvacrol, to study the effects of EOs on rumen fermentation and methane (CH4) production in vitro by in vitro gas production technique.Each dose of each EOs had 3 replicates.The gas production, CH4 content in gas, and pH, volatile fatty acid (VFA) and ammonia nitrogen (NH3-N) concentrations in fermentation fluid after 24 h simulating rumen fermentation cultivation were measured.The results showed as follows: 1) adding different EOs had no significant effect on pH of fermentation fluid in vitro (P>0.05) except for thyme.2) Adding eugenol, D-limonene, anethole and cinnamaldehyde had no significant effect on total VFA concentration in fermentation fluid in vitro (P> 0.05), but the total VFA concentration had a quadratic curve change with thyme or carvacrol concentrations increasing (PQ<0.01).Compared with control group, adding 400 mg/L thyme and carvacrol significantly decreased total VFA concentration (P<0.01).Adding D-limonene, anethole, thyme and carvacrol changed the molar ratio of individual VFA in total VFA.Compared with control group, adding 50 mg/L D-limonene and anethole significantly increased acetate ratio (P<0.05), and significantly decreased propionate ratio (P<0.05), however, adding 400 mg/L D-limonene and anethole significantly decreased acetate ratio (P<0.05), and significantly increased propionate and butyrate ratios (P<0.05).Adding thyme and carvacrol had no effect on acetate ratio (P>0.05), but adding 400 mg/L thyme and carvacrol significantly decreased propionate ratio compared with control group (P<0.05).3) Adding anethole, thyme and carvacrol significant affected NH3-N concentration in fermentation liquid in vitro (P<0.05), and adding 400 mg/L thyme phenol and carvacrol significantly decreased NH3-N concentration compared with control group (P<0.05).4) Adding D-limonene, anethole and cinnamaldehyde had no effect on 24 h fermentation in vitro gas production (P>0.05).Compared with control group, adding thyme and carvacrol with different concentrations all significantly decreased 24 h fermentation in vitro gas production (P<0.01), and showed a quadratic curve change with thyme or carvacrol concentration increasing (PQ<0.01).5) Adding D-limonene, anethole and cinnamaldehyde had no effect on 24 h fermentation in vitro CH4 production (P>0.05).Compared with control group, adding 50 and 100 mg/L eugenol significantly increased 24 h fermentation in vitro CH4 production (P<0.05), and adding 400 mg/L thyme and carvacrol decreased methane production with 84.7% (P<0.05) and 73.9% (P<0.05), respectively.The above results indicate that different EOs had different effects on rumen fermentation and methane production in vitro, which relates to the dose of EOs.In this experiment, the low dose of thyme and carvacrol can promote rumen fermentation, and the high dose of them inhibite rumen fermentation and significantly decrease methane production.