Effect of different combinations and dosages of phytosterols on rumen microbial fermentation in vitro
[Objectives]This study aimed to evaluate the effects of compositions and doses of phytosterols on rumen microbial fermentation in vitro.[Methods]A two-factor experimental design was used in this study.Phytosterols of different phytosterol(campesterol,brassicasterol,stigmasterol and β-sitosterol)and supplemental doses(0,0.03,0.10 and 0.20 μg·mL-1)were added to serum vials containing 60 mL rumen medium and 0.60 g total mixed diet,which were incubated at 39 ℃ for 24 h in a homothermic incubator.Total gas and methane yields in serum bottles were determined dynamically during this incubation.Culture media and dietary residue were collected respectively at the end of incubation for the analysis of dietary nutrient digestibility and microbial metabolites including the concentrations of lactate,ammonia-nitrogen,volatile fatty acid(VFA)and microbial crude protein(MCP).[Results]Phytosterols β-sitosterol at 0.20 µg·mL-1 had greater gas yields than the other treatments(P＜0.05).Increased doses of phytosterols could enhance the concentration of VFA produced by microbial metabolism in vitro(P＜0.01),especially increasing the percentage of acetate,with β-sitosterol showing the greatest effect.Linear regression analysis was performed for the different phytosterol compositions and proportions present in each product,and the result showed that campesterol and β-sitosterol had beneficial effects on in vitro rumen fermentation,while brassicasterol and stigmasterol showed inhibitory effects on the fermentation system.[Conclusions]Adding campesterol and β-sitosterol could promote the growth and metabolism of ruminal microorganisms in vitro,with β-sitosterol at 0.20 μg·mL-1 being the best.
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