Abstract: Previous study in authors' research group have found that 7% bran replacement basal diet can significantly improve the redness value of Longissimus dorsi muscle of Erhualian pigs and improve their meat quality, but its potential physiological and molecular regulatory mechanisms remain unknown. The aim of the study was to identify the candidate metabolites of dietary fiber affecting meat quality traits of Erhualian pigs using non-targeted metabolomics technology and to explore the potential physiological and molecular regulatory mechanism of dietary fiber affecting the meat quality using an in vitro myotubes derived from Erhualian pigs. Differential plasma metabolites between basal diet group and 7% bran replacement basal diet group were detected by non-targeted metabolomics technology in Erhualian pigs, then the correlation between differential plasma metabolites and meat quality phenotype data were analyzed to identify dietary fiber candidate metabolites affecting the meat quality traits of Erhualian pigs. Then the candidate metabolite was used to treat Erhualian pig myotubes in vitro to study its effect on the transformation of muscle fiber types. The results showed that, a total of 9 differential metabolites were identified between the basal diet group and the 7% bran replacement basal diet group, of which 4 differential metabolites had higher level in the basal diet group and 5 differential metabolites had higher level in the 7% bran replacement basal diet group. KEGG pathway analysis showed that plasma differential metabolites of Erhualian pigs were mainly involved in melanin generation pathway, ABC transporter pathway and tyrosine and tryptophan biosynthesis pathway, etc. The plasma metabolite heptadecanoic acid was found to be positively correlated with the 24 h redness value (a_{24 h}) of Longissimus dorsi muscle of Erhualian pigs by correlation analysis with the meat quality phenotype data obtained in previous studies. The results of in vitro cell experiments showed that the expression level of type I muscle fiber type marker gene MyHC I was increased by heptadecanoic acid treatment in Erhualian pig myotube cells. In summary, appropriate dietary fiber supplementation changed the plasma metabolome of Erhualian pigs, and heptadecanoic acid may improve the flesh color of Longissimus dorsi muscle of Erhualian pigs by increasing the expression of MyHC I gene and thus improved the quality of pork.

Key words: Erhualian pigs, dietary fiber, plasma metabolomics, heptadecanoic acid