In vitro evaluation of novel crude extracts produced by actinobacteria for modulation of ruminal fermentation

ABSTRACT We evaluated the inclusion of two crude extracts produced by Streptomyces genus on in vitro dry matter and organic matter digestibility (IVDMD; IVOMD), cumulative gas production, volatile fatty acids (VFA), and methane (CH4) and ammoniacal nitrogen (NH3-N) concentration. The experimental design was randomized blocks with three blocks and four treatments: AMC (1.2 mg/25 mL ruminal inoculum), Caat (1.2 mg/25 mL ruminal inoculum), negative control (no inclusion of extracts), and positive control (sodium monensin, 1.7 mg/25 mL ruminal inoculum). Ruminal fluid samples were collected from three multiparous Holstein dairy cows fitted with ruminal cannula and incubated in a 24-h fermentation assay. There was no effect of crude extract inclusion in comparison with negative control on cumulative gas production in 24 h. However, cumulative gas production was lower when Caat extract was included in comparison with AMC inclusion. The Caat inclusion increased propionic acid concentration and reduced the concentration of butyric acid and acetate:propionate (A:P) ratio in relation to negative control. The CH4 concentration was lower with Caat inclusion in relation to AMC, and the ratio of CH4 concentration to digestible dry matter was lower in the negative control compared with all additives. Caat inclusion decreased the NH3-N concentration, and IVDMD was not altered compared with negative control. Additionally, the inclusion of Caat crude extract increased propionic acid concentration and reduced butyric acid concentration and A:P ratio, without reducing the IVDMD and IVOMD. Caat extract modulates rumen fermentation, increasing available energy and decreasing gas production without causing changes in dry matter and organic matter digestibility.

摘要：本研究评估了链霉菌属（Streptomyces genus）制备的两种粗提物对体外干物质与有机物消化率（in vitro dry matter and organic matter digestibility, IVDMD; IVOMD）、累积产气量、挥发性脂肪酸（volatile fatty acids, VFA）以及甲烷（methane, CH4）和氨态氮（ammoniacal nitrogen, NH3-N）浓度的影响。试验采用随机区组设计，设置3个区组与4种处理：AMC组（1.2 mg/25 mL瘤胃接种物）、Caat组（1.2 mg/25 mL瘤胃接种物）、阴性对照组（不添加粗提物）以及阳性对照组（莫能菌素钠，1.7 mg/25 mL瘤胃接种物）。瘤胃液样本采自3头安装瘤胃瘘管的经产荷斯坦奶牛，并开展24小时发酵试验。
结果显示，与阴性对照组相比，添加粗提物对24小时累积产气量无显著影响；但相较于AMC组，添加Caat提取物的累积产气量更低。与阴性对照组相比，Caat添加可提升丙酸浓度，同时降低丁酸浓度与乙酸:丙酸（A:P）比值。相较于AMC组，Caat添加组的甲烷浓度更低；且阴性对照组的甲烷浓度与可消化干物质的比值低于所有添加剂处理组。Caat添加可降低氨态氮浓度，但对IVDMD无显著影响。此外，添加Caat粗提物可提升丙酸浓度、降低丁酸浓度与A:P比值，且不会降低IVDMD与IVOMD。综上，Caat提取物可调控瘤胃发酵，提升有效能量供给并降低产气量，同时不会改变干物质与有机物消化率。