牛至精油对绵羊瘤胃体外养分降解率、发酵特性及CH4产量的影响

试验旨在研究牛至精油对绵羊瘤胃体外养分降解率、发酵特性及CH₄产量的影响。采用单因素完全随机试验设计,在培养液中分别添加0(CON)、100(EO₁)、400(EO₂)、700(EO₃)和1000 mg·L^-1(EO₄)牛至精油,每组4个重复。发酵48 h后测定养分降解率、发酵参数及不同时间总产气量和CH₄产量。结果表明:1)与CON组相比,干物质降解率、粗蛋白降解率、中性洗涤纤维降解率在EO₁组中均显著升高(P<0.05),在EO₄组中均显著降低(P<0.05),EO₂组中均无显著差异(P>0.05),干物质降解率在EO₃组中显著降低(P<0.05),添加牛至精油对酸性洗涤纤维降解率(ADFD)无显著影响(P>0.05);2)EO₁组pH最低,而总挥发性脂肪酸(TVFA)、丙酸浓度最高,且乙酸浓度显著高于EO₂、EO₃和EO₄(P<0.05),但乙酸/总挥发性脂肪酸显著低于EO₃、EO₄组(P<0.05),乙酸/丙酸显著低于CON组(P<0.05)。与CON组相比,牛至精油组丁酸、丁酸/总挥发性脂肪酸和氨氮浓度显著降低(P<0.05);3)发酵36 h后,总产气量、甲烷产量均随牛至精油的添加而逐渐降低,与CON组相比,EO₁组发酵18~48 h总产气量显著降低(P<0.05),EO₂、EO₃和EO₄组总产气量、CH₄产量在发酵18 h后均显著降低(P<0.05),EO₄组甲烷百分比在发酵12~36 h显著降低(P<0.05)。综上所述,在绵羊瘤胃体外培养液中添加牛至精油能够提高饲粮养分降解率,调控瘤胃发酵,降低总产气量和甲烷产量,体外条件下添加量不应高于100 mg·L^-1。

Effects of oregano essential oil on nutrient degradability,rumen fermentation,and CH4 production in sheep

We evaluated the effects of oregano essential oil on the nutrient degradability, rumen fermentation, and CH₄ production of sheep in an in vitro fermentation system. The experiment had a single-factor design. Oregano essential oil (OEO) was added to the medium at four different levels: 0 (CON), 100 (EO₁), 400 (EO₂), 700 (EO₃), and 1000 mg·L^-1 (EO₄). Each group had four replicates. After fermentation for 48 h, nutrient degradability and fermentation parameters were measured. The total gas and CH₄ production were measured at 1, 3, 6, 9, 12, 18, 24, 36, and 48 h during fermentation. The main results were as follows: 1) Dry matter degradability (DMD), crude protein degradability (CPD), and neutral detergent fiber degradability (NDFD) were significantly increased in the EO₁ group (P<0.05), significantly decreased in the EO₄ group (P<0.05), and unaffected in the EO₂ group (P>0.05) compared with the CON group. The DMD was significantly higher in the EO₃ group than in the CON group (P<0.05). Addition of OEO did not affect the acid detergent fiber degradability (ADFD) (P>0.05); 2) Among all groups, the EO₁ group had the lowest pH but the highest concentrations of total volatile fatty acids (TVFA) and propionate. The acetate concentration was higher in the EO₁ group than in the EO₂, EO₃, and EO₄ groups (P=0.011), however, the percentage of acetate/TVFA was significantly lower in the EO₁ group than in the EO₃ and EO₄ groups (P<0.001), and the ratio of acetate/propionate was significantly lower in the EO₁ group than in the CON group (P<0.05). Compared with the CON group, all the EO groups showed significantly decreased concentrations of butyrate and NH₃-N, and lower butyrate/TVFA ratios (P<0.05); 3) The total gas production and CH₄ production after 36 h of fermentation decreased as the OEO dose increased. Compared with the CON group, the EO₁ group showed significantly decreased total gas production from 18 to 48 h of fermentation (P<0.05), and the EO₂, EO₃, and EO₄ groups showed significantly decreased total gas production and CH₄ production after 18 h of fermentation (P<0.05). Compared with the CON group, all EO groups showed significantly lower CH₄ production from 12 to 36 h of fermentation (P<0.05). In summary, supplementation with oregano essential oil can improve nutrient degradability, regulate rumen fermentation, and decrease total gas and CH₄ production; the optimal supplementation level is less than 100 mg·L^-1 in in vitro fermentation conditions.