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The objective of this study was to evaluate the effect of dietary probiotic supplementation on protein synthesis and flavor compounds in lambs. Two experimental groups were randomly allotted for the 18 three-month-old crossbred ewes of Dorper × Small-Tailed Han sheep. The control group was fed a basic diet, and the probiotic group was supplemented with Clostridium butyricum at 5 g/head on the basis of the control diet (the viable number of Clostridium butyricum was 5.0×108 CFU/g). The pre-feeding was set as 7 days, and the feeding period lasted for 90 days. After that, the selected lambs were transported into the abattoir for slaughter, where the longissimus dorsi muscle was immediately dissected and weighed after slaughter. One part of the muscle samples were stored at -80 ℃ for the determination of enzyme activity and gene expression that related to protein synthesis, and another part was stored at -20 ℃ for the determination of flavor substances. Muscle weight, flavor substances, muscle fiber morphology, enzyme activities, and the expression of protein synthesis genes were determined by gas chromatography mass spectrometry (GC-MS) and real-time fluorescent quantitative polymerase chain reaction (RT-qPCR). The results demonstrated that compared with the control group, the weight of longissimus dorsi muscle in the probiotic group increased significantly (P<0.05), while the diameter and cross-sectional area of muscle fibers increased significantly (P<0.01), indicating that the probiotics were enhanced the muscle weight of lambs. The activity of branched chain aminotransferase (BCAT) and branched-chain α-keto acid dehydrogenase (BCKDH) significantly increased in the muscle of the probiotic group (P<0.05), indicating that the dietary supplementation with probiotics accelerated greatly the metabolism of branched-chain amino acids in lambs. The gene expressions of insulin-like growth factor 1 (IGF-1), protein kinase B (Akt1), mammalian target of rapamycin (mTOR), p70 ribosomal proteinS6 kinase (p70S6K), and eukaryotic translation initiation factor 4E binding protein 1 (4EBP1) in the probiotics group were higher than those in the control group (P<0.05), whereas, the gene expressions of forkhead box protein o3 (FoxO3) and muscle atrophy F-box (MAFbx) were significantly lower than those in the control group (P<0.05). There was no significant difference in the muscle ring-finger protein-1 (MuRF1) gene expression between the two groups (P>0.05). It was confirmed that the probiotics promoted protein synthesis, but inhibited the protein degradation of lambs, when increasing the gene expressions of Akt1, mTOR and p70S6K, and reducing the gene expressions of FoxO3 and MAFbx via the Akt signaling pathway. There was some influence of dietary probiotic supplementation on the composition and relative contents of flavor compounds in lambs. Compared with the control group, the content of hexanal, heptanal, nonanal, and decanal were significantly reduced in the probiotic group (P<0.05), whereas, the content of 1-octanol and 1-octen-3-ol increased significantly (P<0.05). Octanal, nonanal, (E)-2-nonenal, decanal, (E)-2-decenal, dodecanal, 1-octen-3-ol, and phenol greatly contributed to the formation of lamb flavor in the probiotic group, imparting fruit-like, onion-like, sweet, mushroom, grassy and rose-like flavors. Correlation analysis showed that there was a correlation between the critical flavor substances and protein synthesis-related indicators, in which the gene expression of IGF-1 was significantly negatively correlated with the (E)-2-nonenal, decanal and (E)-2-decenal (P<0.05), while positively correlated with the 1-octen-3-ol (P<0.05). The gene expression of Akt1 was negatively correlated with the (E)-2-nonenal (P<0.05). In conclusion, the addition of probiotics into the diet can be expected to improve the protein synthesis level of lambs through the Akt signaling pathway, which in turn affected the flavor of lamb. The finding can also provide a theoretical basis and reference to regulate the quality of lamb via the diet. [ABSTRACT FROM AUTHOR]

【Objective】This experiment was conducted to investigate the effects of compound lactic acid bacteria on growth performance, slaughter performance, meat quality and intestinal microflora of Sunit sheep.【Method】Twelve 3-month-old Sunit sheep with similar body weight were randomly divided into control group（basal diet） and experimental group（basal diet supplemented with compound lactic acid bacteria）, with half male and half female, and slaughtered after feeding for 90 days. The growth performance, slaughter performance and longest back muscle quality of Sunit sheep at the 30th, 60th and 90th day were measured. Meanwhile, fresh feces were collected at the 0th, 30th, 60th and 90th day for high-throughput sequencing to analyze the effects of compound lactic acid bacteria on intestinal microbial diversity and composition of intestinal microflora of Sunit sheep.【Result】Compared with the control group, the total gain and average daily gain of experimental group at the 30th and 90th the day were significantly increased（P<0.05）, the ratio of bone to meat, loin eye area and pH24 after slaughter were significantly higher than those in the control group（P<0.05）, and the cooking loss was extremely significantly lower than that in the control group（P<0.01）. There were no significant differences in other performance and meat quality indexes between control group and experimental group（P>0.05）. The Chao1 and Ace in the experimental group was higher than in the control group（P<0.05）, which showed that feeding lactobacillus was beneficial for improving the diversity of gut microbiota. At the phylum level, gut microbiota of Sunit sheep mainly included Firmicutes and Bacteroidetes in two feeding methods. In the 30th and 90th day, the abundance of Firmicutes in the experimental group was higher than control group（P<0.05）, and the abundance of Proteobacteria was significantly lower than control group（P<0.05）. At the genus level, the abundance of Ruminococcaceae＿UCG＿010, unclassified＿f＿＿Lachnospiraceae, and Alistipes in the experimental group was higher than control group in the 30th day. However, the abundance of Succinivibrio in the experimental group was lower than in the control group（P<0.05）. Compared to control group, the abundance of Ruminococcaceae＿UCG＿010, unclassified＿f＿＿Lachnospiraceae, and Prevotella＿2 in the 60th day and the abundance of Alistipes, Prevotella＿1 and Treponema＿2 in the 90th day increased significantly in the experimental group（P<0.05）, while the abundance of Succinivibrio decreased（P<0.05）. 【Conclusion】In conclusion, lactic acid bacteria, as a natural and green substitute for antibiotics, has a positive impact on improving growth performance, slaughter performance, intestinal microbial composition and meat quality of Sunit sheep, providing theoretical reference for the development of lactic acid bacteria feed and improving the performance of house feeding sheep. [ABSTRACT FROM AUTHOR]

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Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)