Effects of sucralose supplementation on rumen bacterial community, kynuronine pathway and feeding behavior in small-tailed Han sheep

Artificial sweeteners promote feeding behavior in animals. So far, the effect of artificial sweeteners on the structure and metabolites of rumen microbiota has rarely been studied, and the mechanism promoting feeding is unknown. Twelve ewes were divided into two groups: CK and sucralose 300 (SUC300) groups. The dosage of sucralose in the diet was 0 and 300 mg/kg dry matter, respectively. The results showed that sucralose increased feeding behavior in the SUC300 group. Besides, sucralose increased 5-hydroxytryptamine (5-HT) level, and had no effect on alanine aminotransferase (ALT), aspartate aminotransferase (AST), total protein (TP), glucose (GLU), triglycerides (TG) and total cholesterol (TCHO) contents in serum. Next, we compared the rumen flora and metabolites of the CK and SUC300 groups. The rumen bacterial community significantly changed in the SUC300 group, with the abundance of Ralstonia, Dialister, Streptococcus, and Blautia being relatively higher in the SUC300 than in the CK group. One hundred and thirteen different expressed metabolites were detected. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis illustrated that four key metabolic pathways, including tryptophan metabolism, primary bile acid biosynthesis, tyrosine metabolism, and pyrimidine metabolism, were enriched in the SUC300 group. L-kynurenine abundance decreased in the SUC300 group, which was negatively correlated with Bifidobacterium, Bacillus, Blautia, and Dorea and positively correlated with Ruminococcaceae_Ruminococcus and Coprococcus. This study demonstrated that the supplementation of sucralose may reshaped ruminal microorganisms and impacted metabolites by restraining tryptophan metabolism to the kynurenine pathway, promoting 5-HT levels in the blood pool in a way that feeding behavior was enhanced in small-tailed Han sheep.