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.

Red clover extract (RCE) is rich in isoflavones, which have been reported to improve nitrogen utilization in dairy diets. Therefore, the objective of this study was to evaluate the effects of partially replacing soybean meal (SBM) with RCE plus feed-grade urea on lactation performance and nitrogen metabolism in lactating Holstein cows, relative to a slow-release urea (SRU) nitrogen source formulated to provide a similar amount of dietary nitrogen. In a randomized complete block design, 600 cows received one of 3 diets for 35 d (n = 200 per diet): SBM (10.81% SBM), SRU (0.65% SRU replacing 37.74% of SBM), or RCE (0.20% RCE + 0.57% urea replacing 37.74% of SBM). Diets were formulated to be isoenergetic and isonitrogenous. Data were analyzed using a mixed model with diet as a fixed effect and block and pen nested within diet as random effects; the pen was considered the experimental unit. Milk yield and milk composition did not differ between RCE and SBM. DMI and feed efficiency were similar between these treatments, whereas SRU was associated with greater DMI and lower feed efficiency relative to SBM. Compared with SBM, RCE increased urinary purine derivatives and estimated microbial N, whereas concentrations of urea N in milk, plasma, and urine did not differ. Apparent NDF and ADF digestibility were similar between RCE and SBM but were lower with SRU. Differences among diets were also observed in selected blood biochemical and endocrine variables. These findings indicate that, during the 35-d experimental period, partial replacement of SBM with RCE plus urea maintained lactation performance relative to SBM and was associated with higher estimated microbial N compared with SBM, whereas responses to SRU differed in several nitrogen-related measures.

Context: Cotton stalk valorization is limited by high lignification, resulting in waste and environmental issues. Biochar, a pyrolysis-derived material, shows promise in reducing ruminant methane emissions. Aims: This study investigates the effects of cotton stalk biochar (CSB) as a feed additive on rumen fermentation, methane emissions, microbial communities, and nutrient degradation in dairy cows. Methods: Cotton stalks were air-dried, cut into 2–3 cm segments, oven-dried at 105°C for 6 h, ground through an 80-mesh sieve, and pyrolyzed under N ₂ (0.5 L/min) at 13.3°C/min to 400°C with a 3 h hold to produce CSB. CSB was added to diets at 0%, 3%, and 6% levels. Each treatment was conducted in triplicate, with two fermentation bottles for each replicate. Rumen fermentation was simulated using an in vitro static culture method with rumen fluid from Holstein dairy cows. Fermentation parameters, gas production, nutrient disappearance, microbial populations, and metabolites were analyzed. Key Results: CSB addition increased rumen pH and significantly reduced total gas, CH ₄ , CO ₂ , and H ₂ production ( P < 0.05). Total volatile fatty acid concentration decreased with increasing CSB levels. However, no significant changes were observed in microbial diversity or total DNA copy numbers of bacteria and methanogens. Metabolomics revealed that CSB altered key metabolites involved in amino acid (such as citrulline) and fatty acid metabolism (such as pyruvic acid and undecanoic acid). As CSB levels increased, cellulase activity decreased, thereby inhibiting dry matter and fiber loss rates and further reducing gas production. Conclusions: In conclusion, the addition of 3% or 6% biochar to the feed of cows was able to minimise ruminal gas production. However, it may act by inhibiting the ruminal fermentation (NDF degradation) pathway. Implication.: The addition of 3% CSB can reduce in vitro gas production in the rumen of dairy cows.