Effects of non-pelleted or pelleted low-native grass and pelleted high-native grass diets on meat quality by regulating the rumen microbiota in lambs

Diet modulates the rumen microbiota, which in turn can impact the animal performance. The rumen microbiota is increasingly recognized for its crucial role in regulating the growth and meat quality of the host. Nevertheless, the mechanism by which the rumen microbiome influences the fatty acid and amino acid profiles of lambs in the grass feeding system remains unclear. This study aimed to evaluate the effects of different native grass-based diets on animal performance, meat quality, fatty acid compositions, amino acid profiles, and rumen microbiota of lamb. Seventy-two Ujumqin lambs were randomly assigned into three treatments according to the initial body weight (27.39 +/- 0.51 kg) and age (6 months +/- 6 days). The lambs received three diets: (i) non-pelleted native grass hay with 40% concentrate diet; the native grass and concentrate were fed individually; (ii) pelleted native grass hay with 40% concentrate diet (PHLC); (iii) pelleted native grass hay with 60% concentrate diet (PHHC). The results showed that among the three groups, the PHHC and PHLC diets had markedly (P < 0.05) higher average daily gain and pH(45 min), respectively. All amino acid levels were significantly (P < 0.05) decreased in the PHHC diet than in the PHLC diet. The principal coordinate analysis of the ruminal microbiota indicated the markedly distinct separation (P = 0.001) among the three groups. In addition, the correlation analysis showed that the Rikenellaceae_RC9_gut_group, Prevotellaceae_UCG-003, Succinivibrio, and Succiniclasticum were significantly (P < 0.05) associated with most of the fatty acid and amino acid profiles. The correlation analysis of the association of microbiome with the meat quality provides us with a comprehensive understanding of the composition and function of the rumen microbial community, and these findings will contribute to the direction of future research in lamb. IMPORTANCE Diet modulates the gut microbiome, which in turn impact the meat quality, yet few studies investigate the correlation between the rumen microbiome and the fatty acid profile of meat. Here, the current study develops an experiment to investigate the correlation of the rumen microbiome and fatty acid profile of meat: rumen microbiome responses to feed type and meat quality. The results indicated a unique microbiota in the rumen of lamb in response to diets and meat quality. Associations between utilization and production were widely identified among the affected microbiome and meat quality, and these findings will contribute to the direction of future research in lamb.