The purpose of this study is to investigate the potential effects of 5-hydroxytryptophan (5-HTP) duodenal perfusion on melatonin (MT) synthesis in the gastrointestinal (GI) tract of sheep. 5-hydroxytryptophan is a precursor in the melatonin synthetic pathway. The results showed that this method significantly increased melatonin production in the mucosa of all segments in GI tract including duodenum, jejunum, ileum, cecum and colon. The highest melatonin level was identified in the colon and this indicates that the microbiota located in the colon may also participate in the melatonin production. In addition, portion of the melatonin generated by the GI tract can pass the liver metabolism and enters the circulation via portal vein. The current study provides further evidence to support that GI tract is the major site for melatonin synthesis and the GI melatonin also contributes to the circulatory melatonin level since plasma melatonin concentrations in 5-HTP treated groups were significantly higher than those in the control group. In conclusion, the results show that 10–50 mg of 5-HTP flowing into the duodenum within 6 h effectively improve the production of melatonin in the GI tract and melatonin concentration in sheep blood circulation during the day.

This study aimed to investigate the effects of thymol supplementation in health care sand on growth performance, serum biochemical parameters, fecal microbial diversity, and fecal metabolites in Grey King squabs. A total of 160 healthy 28-day-old Grey King squabs were selected and randomly assigned to four treatment groups: the CON, 2%Thy, 3%Thy, and 4%Thy groups. Each group consisted of 10 replicates with four squabs per replicate, resulting in a total of 40 squabs per group. Under identical feeding management conditions and dietary nutrient levels, squabs in the CON group received the basal diet plus 5 g of health care sand; those in the 2%Thy group received the basal diet plus 5 g of health care sand containing 2% thymol; those in the 3%Thy group received the basal diet plus 5 g of health care sand containing 3% thymol; and those in the 4%Thy group received the basal diet plus 5 g of health care sand containing 4% thymol. The experiment lasted for 30 days. During the experimental period, the pigeons were housed in cages measuring 45 cm × 50 cm × 60 cm. Each pigeon was provided with 40 g of diet and 5 g of health care sand daily and had free access to water. After Benjamini–Hochberg false discovery rate correction, no significant differences were observed in growth performance, body measurements, apparent nutrient retention, or energy metabolizability among treatments (q > 0.05). However, thymol-supplemented groups exhibited significantly increased serum total antioxidant capacity and superoxide dismutase, glutathione peroxidase, and catalase activities, together with decreased malondialdehyde levels (q < 0.05). Fecal microbiome and metabolomic analyses were restricted to the CON and 3%Thy groups, with the 3%Thy group selected after evaluation of the phenotypic and physiological responses rather than being prespecified before the experiment. These omics comparisons were therefore considered exploratory. No statistically significant difference in overall fecal microbial community composition was detected between the two groups, whereas 17 candidate differential fecal metabolite features were observed. These features were mainly putatively annotated as lipids and lipid-like molecules, organic acids and derivatives, organoheterocyclic compounds, and benzenoids. Among the supplementation levels evaluated, the 3%Thy group showed comparatively favorable numerical responses in several measured parameters and may be considered a candidate level for further investigation. However, the present findings do not establish an optimal thymol supplementation level, and the biological significance of the exploratory fecal omics results requires further validation.

Sea buckthorn polysaccharide (SP) has antioxidant and anti-inflammatory activities, but its effects in tumbler pigeons remain unclear. Eighty-four male tumbler pigeons were assigned to four treatments receiving diets containing 0, 100, 200, or 400 mg/kg effective SP for 60 days, with seven replicate cages per treatment. SP supplementation enhanced serum antioxidant capacity and modulated inflammatory cytokine profiles, with the most pronounced overall responses observed at 200 mg/kg. The SP200 and SP400 groups also had lower serum lactate, total cholesterol, and triglyceride concentrations than the control group, whereas most blood gas, electrolyte, and acid–base variables were unaffected. Because SP200 produced the strongest antioxidant and cytokine responses, the CON and SP200 groups were selected for untargeted serum metabolomics. This analysis identified 68 and 79 differential metabolites in positive- and negative-ion modes, respectively. KEGG enrichment analysis ranked purine metabolism, phenylalanine metabolism, primary bile acid biosynthesis, and the citrate cycle among the leading pathways; however, none remained significant after Benjamini–Hochberg correction. Exploratory Spearman analysis revealed associations between selected metabolites and phenotypic indicators. Taken together, these findings indicate that 200 mg/kg SP may be an effective dietary supplementation level for improving antioxidant and inflammatory status in tumbler pigeons, while the associated metabolomic changes warrant further targeted validation.