McDermott Katie, Lee Michael R F, McDowall Kenneth J, Greathead Henry M R
Faculty of Biological Sciences, School of Biology, University of Leeds, Leeds, United Kingdom.
Rothamsted Research, North Wyke, Okehampton, United Kingdom.
Front Microbiol. 2020 Sep 24;11:531404. doi: 10.3389/fmicb.2020.531404. eCollection 2020.
Environmental pressures of ruminant production could be reduced by improving digestive efficiency. Previous attempts to manipulate the rumen microbial community have largely been unsuccessful probably due to the influencing effect of the host. Using an consecutive batch culture technique, the aim of this study was to determine whether manipulation was possible once the bacterial community was uncoupled from the host. Two cross inoculation experiments were performed. Rumen fluid was collected at time of slaughter from 11 Holstein-Friesian steers from the same herd for Experiment 1, and in Experiment 2 were collected from 11 Charolais cross steers sired by the same bull and raised on a forage only diet on the same farm from birth. The two fluids that differed most in their dry matter disappearance (IVDMD; "Good," "Bad") were selected for their respective experiment. The fluids were also mixed (1:1, "Mix") and used to inoculate the model. In Experiment 1, the mixed rumen fluid resulted in an IVDMD midway between that of the two rumen fluids from which it was made for the first 24 h batch culture (34, 29, 20 g per 100 g DM for the Good, Mix, and Bad, respectively, < 0.001) which was reflected in fermentation parameters recorded. No effect of cross inoculation was seen for Experiment 2, where the Mix performed most similarly to the Bad. In both experiments, IVDMD increased with consecutive culturing as the microbial population adapted to the conditions and differences between the fluids were lost. The improved performance with each consecutive batch culture was associated with reduced bacterial diversity. Increases in the genus were identified, which may be, at least in part, responsible for the improved digestive efficiency observed, whilst declined by 50% over the study period. It is likely that along with host factors, there are individual factors within each community that prevent other microbes from establishing. Whilst we were unable to manipulate the bacterial community, uncoupling the microbiota from the host resulted in changes in the community, becoming less diverse with time, likely due to environmental heterogeneity, and more efficient at digesting DM.
通过提高消化效率可以减轻反刍动物生产的环境压力。以往操纵瘤胃微生物群落的尝试大多未成功，这可能是由于宿主的影响作用。本研究旨在利用连续批次培养技术，确定一旦细菌群落与宿主解耦，是否有可能进行操纵。进行了两个交叉接种实验。实验1中，从同一牛群的11头荷斯坦 - 弗里生阉牛屠宰时采集瘤胃液；实验2中，从同一头公牛所生、自出生起就在同一农场仅以草料为食饲养的11头夏洛来杂交阉牛采集瘤胃液。在各自的实验中，选取了干物质消失率（IVDMD；“优”、“劣”）差异最大的两种瘤胃液。这两种瘤胃液也进行了混合（1:1，“混合”）并用于接种模型。在实验1中，混合瘤胃液在前24小时批次培养中产生的IVDMD介于用于制备它的两种瘤胃液的IVDMD之间（“优”、“混合”和“劣”分别为每100克干物质34克、29克和20克，P<0.001），这在记录的发酵参数中得到体现。实验2未观察到交叉接种的效果，其中“混合”组的表现与“劣”组最为相似。在两个实验中，随着微生物群体适应条件且不同瘤胃液之间的差异消失，IVDMD随着连续培养而增加。连续批次培养性能的改善与细菌多样性降低有关。确定了某属细菌的增加，这可能至少部分地导致了观察到的消化效率提高，而在研究期间另一属细菌减少了50%。除宿主因素外，每个群落中可能还存在个体因素，阻止其他微生物定殖。虽然我们无法操纵细菌群落，但使微生物群与宿主解耦导致群落发生变化，随着时间推移多样性降低，这可能是由于环境异质性，并且在消化干物质方面更高效。
