State Key Laboratory of Grassland Agro-Ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, P.R. China.
Engineering Research Center of Grassland Industry, Ministry of Education, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, P.R. China.
J Anim Sci. 2020 Jul 1;98(7). doi: 10.1093/jas/skaa228.
Ruminal cellulolytic bacteria could be a diagnostic tool for determining the subacute rumen acidosis (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 d, and sampling was for 63 d. 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, ruminal bacterial DNA, rumen digesta, and muscle FAs. The lambs were classified into the lower cellulolytic bacteria (LCB, n = 10) group and the higher cellulolytic bacteria (HCB, n = 10) group 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 with 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 in the rumen digesta of lambs with the HCB were higher (P < 0.05), while the polyunsaturated fatty acids 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 the 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 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 the meat of sheep.
瘤胃纤维分解菌可以作为个体反刍动物亚急性瘤胃酸中毒（SARA）风险的诊断工具；然而，很少有研究调查瘤胃纤维分解菌丰度对反刍动物瘤胃消化物和肌肉脂肪酸（FA）组成的影响。因此，本研究旨在评估瘤胃纤维分解菌变化对育肥羔羊相同饮食的瘤胃发酵、瘤胃消化物和肌肉 FA 组成的影响。48 只羔羊在单独的单元中饲养，并喂食由 20%草料和 80%浓缩物组成的高浓度日粮。所有羔羊均适应日粮和设施 14 天，并进行 63 天采样。实验结束时，屠宰后采集瘤胃液、瘤胃消化物和背最长肌，以测量挥发性脂肪酸、瘤胃细菌 DNA、瘤胃消化物和肌肉 FA。根据瘤胃中 pH 敏感纤维分解菌（白色瘤胃球菌、黄色瘤胃球菌、纤维丁酸弧菌和产丁酸梭菌）的丰度，将羔羊分为低纤维分解菌（LCB，n=10）组和高纤维分解菌（HCB，n=10）组。瘤胃乙酸浓度与黄色瘤胃球菌、纤维丁酸弧菌和产丁酸梭菌的数量呈正相关（P<0.05，r>0.296），而丙酸和戊酸浓度与纤维丁酸弧菌和产丁酸梭菌的数量呈负相关（P<0.05，r>0.348）。与 LCB 组相比，HCB 组的乙酸（P=0.018）和乙酸与丙酸的比例（P=0.012）较高，但戊酸比例较低（P=0.002）。HCB 组羔羊瘤胃消化物中的偶数链 FA 和奇数链及支链脂肪酸的比例较高（P<0.05），而多不饱和脂肪酸低于 LCB 组羔羊（P<0.05），但两组肉中的 FA 比例相似。HCB 组羔羊肉中的 C17:0 比例低于 LCB 组羔羊（P=0.033）。HCB 组羔羊瘤胃消化物和肉中的共轭亚油酸比例均高于 LCB 组（P=0.046）。这些结果表明，瘤胃纤维分解菌可以改变瘤胃消化物中的 FA 组成，并进一步影响绵羊肌肉中的 FA 组成。
