Influence Of Different Trace Elements Mixtures On Microorganism Diversity And The Level Of Lactic Acid And Mycotoxins Of Liquid Diet Fermented With Probiotics

The thesis consists of two parts:(1) Study on the influence of different trace elements mixture on bacterial diversity and fermentation characteristics of fermented liquid diet(FLF);(2) Study on the influence of different trace elements mixture on fungal diversity and mycotoxin level of fermented liquid diet.Cu2+, Zn2+, Fe2+ and I- are often supplemented to the diet of suckling and early weaning piglets, but little information is available regarding the effects of different Cu2+, Zn2+, Fe2+ and I- mixtures on bacteria growth, diversity and fermentation characteristics of fermented liquid diet for piglets. Pyrosequencing was performed to investigate the effect of Cu2+, Zn2+, Fe2+ and I- at different concentrations on the diversity, growth and fermentation characteristics of bacteria in the liquid diet fermented with Bacillus subtilis and Enterococcus faecalis under air-tight condition. Results showed that the mixtures of Cu2+, Zn2+, Fe2+ and I- at different concentrations promoted Bacillus growth, increased bacterial diversity and lactic acid production and lowered pH to about 5. The importance of Cu2+, Zn2+, Fe2+ and I- is different for Bacillus growth with the order Zn2+> Fe2+>Cu2+> I- in a 21-d fermentation and Cu2+>I->Fe2+>Zn2+ in a 42-d fermentation. Cu2+, Zn2+, Fe2+ and I- is recommended at a level of 150, 60, 150 and 0.6 mg/kg respectively for the production of fermented liquid diet with Bacillus subtilis. The findings improve our understanding of the influence of trace elements on liquid diet fermentation with probiotics and support the proper use of trace elements in the production of fermented liquid diet for piglets.Pyrosequencing and enzyme-linked immunosorbent assay were performed to investigate the effect of Cu2+, Zn2+, Fe2+ and I- mixture on the growth of fungi and the concentration of mycotoxins in fermented liquid diet.. Results showed that Cu2+ had the most important role in suppressing the growth of Aspergillus compared with Zn2+, Fe2+ and I-, addition of Cu2+ at 200 mg/kg combined with Zn2+, Fe2+ and I- to the fermented liquid diet effectively inhibited the growth of Aspergillus and decreased the concentration of AFB1. Ability of Zn2+ and Fe2+ was higher than that of Cu2+ in decreasing the growth of Fusarium and addition of Zn2+ at 160 mg/kg or Fe2+ at 150 mg/kg mixed with other trace elements to the fermented liquid diet minimized the growth of Fusarium, Cu2+ and Fe2+ is the first important ions in controlling the concentration of DON and ZEN, respectively and the elevated levels of Cu2+ and Fe2+ decrease the concentration of ZEN. These findings help farmers effectively use trace elements mixture in inhibiting the growth and metabolism of mycotoxin-producing fungi in the production of high quality fermented liquid diet.