Objective  Effects of major ingredients used in formulating fermented livestock forage on probiotics in animals fed with it were analyzed.

  Method  Brown sugar, fish meal, soybean meal, and their combinations were used to formulate liquid culture media in an orthogonal experiment. Structure and diversity of the microbial community in the fermentation broths were determined using the high throughput 16S rDNA sequencing technique.

  Result  The fermentation broth became darker as the concentration increased. The addition of soybean or fish meal raised the contents of organic matters and nitrogen, and the fermentation significantly altered the microbial community with a much-enriched diversity and abundance of the broth. At the beginning of the fermentation, Proteobacteria was the predominant phylum with Xanthomonas being the outstanding genus. In the end, Firmicutes with genera Lactobacillus and Weissella became dominant. The microbial community was significantly affected by the ingredients included in the fermentation medium. For instance, brown sugar enhanced the proliferation of Pseudomonas,Xanthomonas, Weissella, Pediococcus, and Lactobacillales, fish meal facilitated that of Psychrobacter, Weissella, and Pseudomonas but inhibited Lactobacillales, while soybean meal promoted the growth of Acetobacter, Lactobacillales, Psychrobacter, Weissella, and Pediococcus.

  Conclusion  It appeared that a culture medium high on brown sugar and soybean meal but low on fish meal could significantly enhance the abundance of Lactobacillus and Weissella in the fermentation broth to be use as a forage for feeding the livestock.