Table_1_Enhancing rumen microbial diversity and its impact on energy and protein metabolism in forage-fed goats.DOCX

IntroductionThis study explores if promoting a complex rumen microbiota represents an advantage or a handicap in the current dairy production systems in which ruminants are artificially reared in absence of contact with adult animals and fed preserved monophyte forage.
MethodsIn order to promote a different rumen microbial diversity, a total of 36 newborn goat kids were artificially reared, divided in 4 groups and daily inoculated during 10 weeks with autoclaved rumen fluid (AUT), fresh rumen fluid from adult goats adapted to forage (RFF) or concentrate (RFC) diets, or absence of inoculation (CTL). At 6 months of age all animals were shifted to an oats hay diet to determine their ability to digest a low quality forage.
Results and discussionEarly life inoculation with fresh rumen fluid promoted an increase in the rumen overall microbial diversity which was detected later in life. As a result, at 6 months of age RFF and RFC animals had higher bacterial (+50 OTUs) and methanogens diversity (+4 OTUs) and the presence of a complex rumen protozoal community (+32 OTUs), whereas CTL animals remained protozoa-free. This superior rumen diversity and presence of rumen protozoa had beneficial effects on the energy metabolism allowing a faster adaptation to the forage diet, a higher forage digestion (+21% NDF digestibility) and an energetically favourable shift of the rumen fermentation pattern from acetate to butyrate (+92%) and propionate (+19%) production. These effects were associated with the presence of certain rumen bacterial taxa and a diverse protozoal community. On the contrary, the presence of rumen protozoa (mostly Entodinium) had a negative impact on the N metabolism leading to a higher bacterial protein breakdown in the rumen and lower microbial protein flow to the host based on purine derivatives urinary excretion (-17% to -54%). The inoculation with autoclaved rumen fluid, as source of fermentation products but not viable microbes, had smaller effects than using fresh inoculum. These findings suggest that enhancing rumen microbial diversity represents a desirable attribute when ruminants are fed forages in which the N supply does not represent a limiting factor for the rumen microbiota.

## 引言
本研究旨在探究，在当前反刍动物人工饲养且不接触成年个体、仅饲喂单一保存饲草的奶牛养殖系统中，强化复杂瘤胃微生物群（rumen microbiota）究竟是优势还是劣势。

## 方法
为构建差异化的瘤胃微生物多样性，本研究共选取36头新生山羊羔进行人工饲养，将其随机分为4组，在10周内每日分别接种以下接种物：灭菌瘤胃液（autoclaved rumen fluid, AUT）、适应饲草型日粮的成年山羊新鲜瘤胃液（fresh rumen fluid from adult goats adapted to forage, RFF）、适应精补型日粮的成年山羊新鲜瘤胃液（fresh rumen fluid from adult goats adapted to concentrate, RFC），以及不进行接种的空白对照组（control, CTL）。待所有受试动物长至6月龄时，将其日粮更换为燕麦干草，以测定其对低品质饲草的消化能力。

## 结果与讨论
新生期接种新鲜瘤胃液可提升瘤胃整体微生物多样性，且该效应可在受试动物后续生长阶段持续存在。结果显示，6月龄时，RFF组与RFC组山羊的细菌多样性（较对照组增加50个操作分类单元（operational taxonomic unit, OTUs））、产甲烷古菌（methanogens）多样性（较对照组增加4个OTUs）均显著更高，且形成了复杂的瘤胃原生动物群落（较对照组增加32个OTUs）；而CTL组山羊始终未检测到瘤胃原生动物。
这种优势的瘤胃微生物多样性与瘤胃原生动物的存在，对能量代谢产生了显著有益影响：受试动物可更快适应饲草日粮，饲草消化率显著提升（中性洗涤纤维（neutral detergent fiber, NDF）消化率提高21%），且瘤胃发酵模式从乙酸型向丁酸型（产量提升92%）与丙酸型（产量提升19%）转变，更利于宿主获取能量。上述效应与特定瘤胃细菌类群及多样化原生动物群落的存在密切相关。
与之相反，瘤胃原生动物（主要为内毛虫属（Entodinium））的存在会对氮代谢产生负面影响：瘤胃内细菌蛋白质分解程度升高，且基于尿中嘌呤衍生物排泄量计算的宿主获得微生物蛋白流量降低17%~54%。
以灭菌瘤胃液作为接种物（仅含发酵产物而非活微生物）所产生的干预效应，弱于新鲜瘤胃液接种。
本研究结果表明，当反刍动物饲喂的饲草其氮供应不会成为瘤胃微生物群的限制因素时，强化瘤胃微生物多样性是一项极具价值的养殖优化策略。