PSVIII-20 - Ruminal cellulolytic bacteria abundance leads to the variation in fatty acids in the rumen digesta and muscle of fattening lambs

This study aimed to evaluate the effect of the variation of rumen cellulolytic bacteria on the composition of rumen digesta and muscle fatty acids of fattening lambs fed an identical diet. Forty-eight lambs (BW: 30 ± 1.68 kg) were reared in individual units and fed a high-concentrate diet consisting of 20% forage and 80% concentrate for 63 days. At the end of the experiment, the rumen fluid, rumen digesta and longissimus dorsi were collected for the measurement of VFA, ruminal bacterial DNA, rumen contents and muscle FAs. Ruminal cellulolytic bacteria could be a diagnostic tool for determining SARA risk in individual ruminants, so the lambs were classified into the group with the least cellulolytic bacteria (LCB, n = 10) and the most cellulolytic bacteria (MCB, n = 10) according to the abundances of the main cellulolytic bacteria (Ruminococcus albus, Ruminococcus flavefaciens, Fibrobacter succinogenes and Butyrivibrio fibrisolvens) in the rumen. The results showed that the proportion of acetate in the MCB group was higher than that in the LCB group (P = 0.018), and the proportion of valerate (P = 0.002) and acetate to propionate ratio (P = 0.012) in the MCB group was lower than those in the LCB group. The proportion of OBCFA (especially iso FAs) in the rumen content of lambs in the MCB group was higher than that in lambs in the LCB, the ratio of PUFAs decreased in the lambs in the LCB, but these FAs in muscle were similar between the two groups. These results indicated that rumen cellulolytic bacteria could affect the FA composition of the rumen content (biohydrogenation, isomerization, and bacterial OBCFA), which could finally lead to the variation in FA compositions in rumen content and muscle tissue when lambs are fed an identical diet.