Ruminal cellulolytic bacteria could be a diagnostic tool for determining SARA risk in individual ruminants; however, a limited number of studies have investigated the effects of the abundance of ruminal cellulolytic bacteria on the fatty acid (FA) composition of the rumen digesta and the muscle of sheep. Thus, the objective of this study was to evaluate the effect of the variation of rumen cellulolytic bacteria on the rumen fermentation, rumen digesta and muscle FA composition of fattening lambs fed an identical diet. Forty-eight lambs were reared in individual units and fed a high-concentrate diet consisting of 20% forage and 80% concentrate. All lambs were adapted to diets and facilities for 14 days and sampling was for 63 days. At the end of the experiment, the rumen fluid, rumen digesta and longissimus dorsi were collected after slaughter for the measurement of volatile fatty acids (VFA), ruminal bacterial DNA, rumen digesta and muscle FAs. The lambs were classified into the lower cellulolytic bacteria group (LCB, n=10) and the higher cellulolytic bacteria group (HCB, n=10) according to the abundance of pH-sensitive cellulolytic bacteria (Ruminococcus albus, Ruminococcus flavefaciens, Fibrobacter succinogenes and Butyrivibrio fibrisolvens) in the rumen. Ruminal acetate concentration was positively correlated with the number of R. flavefaciens, F. succinogenes and B. fibrisolvens (P < 0.05, r > 0.296), whereas propionate and valerate concentrations were negatively correlated with the amount of F. succinogenes and B. fibrisolvens (P < 0.05, r > 0.348). Compared to the LCB group, the acetate (P = 0.018) as well as acetate to propionate ratio (P = 0.012) in the HCB group was higher, but the valerate ratio was lower (P = 0.002). The proportions of even-chain FAs and odd- and branched-chain fatty acid (OBCFA) in the rumen digesta of lambs with the HCB were higher (P < 0.05), while the PUFA decreased than those in the LCB lambs (P < 0.05), but those FA proportions in the meat were similar between the two groups. The proportion of C17:0 in meat of lambs in the HCB group was lower than that of lambs in the LCB group (P = 0.033). The proportions of conjugated linoleic acid (CLA) in rumen digesta and meat were both higher in the HCB group than that in the LCB group (P = 0.046). These results indicated that the ruminal cellulolytic bacteria can alter the FA compositions in rumen digesta and further influenced the FA compositions in meat of sheep.

中文翻译：

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瘤胃纤维素分解细菌的丰度导致瘤胃消化物中和育肥羔羊肉中脂肪酸的变化。

瘤胃纤维素分解细菌可能是确定单个反刍动物中SARA风险的诊断工具。然而，有限的研究已经研究了丰富的瘤胃纤维素分解细菌对瘤胃消化物和绵羊肌肉的脂肪酸（FA）组成的影响。因此，本研究的目的是评估瘤胃纤维素分解细菌的变化对饲喂相同日粮的增肥羔羊的瘤胃发酵，瘤胃消化物和肌肉FA组成的影响。单独饲养48只羔羊，饲喂高浓度日粮，其中包括20％的草料和80％的精料。所有羔羊均适应饮食和适应环境14天，采样63天。实验结束时，瘤胃液，瘤胃消化物和背最长肌屠宰后收集，用于测量挥发性脂肪酸（VFA），瘤胃细菌DNA，瘤胃消化物和肌肉FA。根据丰pH敏感纤维素分解菌（较高纤维素分解菌组（HCB，N = 10）羔羊分为下部纤维素分解菌组（LCB，N = 10）和瘤胃球菌球菌，瘤胃球菌属球菌，Fibrobacter琥珀酸和瘤胃中的丁酸纤维。瘤胃酸甲酯浓度呈正数相关R.球菌，F.琥珀酸和B. fibrisolvens（P <0.05，[R> 0.296），而丙酸和戊酸浓度与琥珀酸杆菌和纤溶芽孢杆菌的含量呈负相关（P <0.05，r > 0.348）。与LCB组相比，HCB组中的乙酸盐（P = 0.018）以及乙酸与丙酸酯的比率（P = 0.012）较高，但戊酸的比率较低（P = 0.002）。HCB羔羊瘤胃消化物中偶数链脂肪酸，奇数和支链脂肪酸（OBCFA）的比例较高（P <0.05），而PUFA则比LCB羔羊的比例低（P<0.05），但两组中肉中的FA含量相似。HCB组的羔羊肉中C17：0的比例低于LCB组的羔羊肉中C17：0的比例（P = 0.033）。HCB组中瘤胃消化物和肉中共轭亚油酸（CLA）的比例均高于LCB组（P = 0.046）。这些结果表明，瘤胃纤维素分解细菌可以改变瘤胃消化物中的FA组成，并进一步影响绵羊肉中的FA组成。