Saccharomyces cerevisiae fermentation products (SCFP) stabilizes the rumen microbiome of lactating dairy cows during subacute ruminal acidosis (SARA)

The effects of a Saccharomyces cerevisiae fermentation product (SCFP) on the composition and functionality of microbial communities in the rumen were determined in vitro and in vivo under normal and subacute ruminal acidosis (SARA) conditions. In the in-vivo trail eight rumen-cannulated lactating dairy cows were used in a cross-over design. During the first of the 5-week experimental period, cows were randomly assigned to treatment, i.e. SCFP (Original XPC, Diamond V, Cedar Rapids, IA) or control. During the second experimental period, treatments were reversed. Experimental periods were separated by a two-week wash out period. During each period, the 4 cows on the SCFP treatment were supplemented with 14 g/d of SCFP in 126 g of ground corn. The other four cows received 140 g ground corn only. During the first 4 wk of each experimental period, all cows received a basal total mixed ration. During week 5 of both experimental periods, a SARA challenge was conducted in all cows by replacing 208 g/kg of the basal diet with pellets of ground wheat and barley (50:50 on a weight basis). Bacterial communities in rumen liquid digesta, were examined by 454 pyrosequencing and real-time quantitative PCR, and their functionality was predicted using PICRUSt and shotgun metagenomics. Across diets, SCFP increased Prevotella brevis, Ruminococcus flavefaciens, ciliate protozoa, and Bifidobacterium spp. Several of the adverse impacts of the SARA challenge, including the reductions of the richness of diversity of the rumen microbiome, in the abundance of Bacteroidetes and in the population of ciliate protozoa were attenuated by SCFP. Several changes in the predicted functionality of the rumen microbiome due to SARA and considered adverse, were also reduced by SCFP. Our result shows that SCFP boosts beneficial rumen bacteria, which is of particulate importance during unfavourable conditions in the rumen, such as SARA. The impact of SCFP on the health and production of dairy cows of may, therefore, be mediated though its favourable effects on beneficial rumen microorganisms. Determination of the full impact of changes in the predicted functionality of the gut microbiota due to the SARA challenges and SCFP supplementation on the production and health of cows remain requires further study.

本研究针对正常及亚急性瘤胃酸中毒（subacute ruminal acidosis, SARA）两种状态，分别通过体外与体内试验，探究酿酒酵母发酵产物（Saccharomyces cerevisiae fermentation product, SCFP）对瘤胃微生物群落组成与功能的影响。体内试验选取8头安装瘤胃瘘管的泌乳奶牛，采用交叉试验设计：在为期5周的首个试验阶段，奶牛被随机分配至SCFP组或对照组，其中SCFP组饲喂商品名Original XPC的SCFP（生产商Diamond V，坐落于艾奥瓦州锡达拉皮兹市），对照组则给予空白对照；第二个试验阶段则互换两组处理方案。两个试验阶段之间设置为期2周的洗脱期。每个试验阶段内，SCFP组的4头奶牛每日将14 g SCFP添加至126 g粉碎玉米中饲喂，对照组4头奶牛则仅饲喂140 g粉碎玉米。每个试验阶段的前4周，所有奶牛均饲喂基础全混合日粮；两个试验阶段的第5周，通过以粉碎小麦与大麦按重量比50:50制成的颗粒替代208 g/kg的基础日粮，对所有奶牛开展SARA攻毒试验。采用454焦磷酸测序与实时荧光定量PCR对瘤胃液态食糜中的细菌群落进行分析，并通过PICRUSt与宏基因组鸟枪法预测其功能。整体而言，SCFP可提升瘤胃内短普雷沃氏菌（Prevotella brevis）、黄色瘤胃球菌（Ruminococcus flavefaciens）、纤毛原生动物与双歧杆菌属（Bifidobacterium spp.）的相对丰度。SARA攻毒带来的多项不良影响，包括瘤胃微生物组的多样性与丰富度降低、拟杆菌门（Bacteroidetes）丰度下降以及纤毛原生动物种群数量减少，均可通过SCFP得到缓解。SARA诱导的瘤胃微生物组预测功能的多项不良变化，同样可被SCFP抑制。本研究结果表明，SCFP可促进有益瘤胃细菌的增殖，而在瘤胃不良状态（如SARA）下，这一作用尤为关键。因此，SCFP对泌乳奶牛健康与生产性能的影响，可能通过其对有益瘤胃微生物的调控作用实现。明确SARA攻毒与SCFP补充所引发的肠道微生物组预测功能变化对奶牛生产性能与健康的全面影响，仍需开展进一步研究。