[Effects of nisin on in vitro fermentation, methanogenesis and functional microbial populations of the rumen].

ABSTRACT

Objective: This study was conducted to evaluate the effects of nisin on in vitro fermentation, methanogenesis and functional microbial populations of the rumen. Methods: The negative control did not contain any additives. Monensin (5 µmol/L) was added as positive control. Nisin was added at 3 doses3 (NI-3), 9 (NI-9), and 27 mg/100 mL (NI-27). Each treatment contained 4 replicates. Gas and methane production was measured at 0, 3, 6, 9, 12, and 24 h after incubation. Samples of culture were collected at 24 h, and used to measure rumen fermentation parameters and functional microbial populations. Results: Compared with negative control, both nisin and monensin addition dramatically reduced gas and methane production (P<0.05). Nisin addition had no effect on pH, dry matter degradability, and organic matter degradability (P0.05). Ammonia concentration was reduced by NI-9 (P<0.05), but was not influenced by NI-3 and NI-27 (P0.05). In contrast, monensin addition significantly lowered dry matter degradability, organic matter degradability, and ammonia concentration (P<0.05), but had no influence on pH (P0.05). Compared with negative control, both nisin and monensin addition significantly reduced acetate concentration and acetate-propionate ratio (P<0.05), and increased propionate concentration (P<0.05). Quantitative real-time PCR results showed that both nisin and monensin addition had no effects on the populations of total bacteria and Bacteroides (P0.05). Compared with negative control, the populations of protozoa, methanogens, fungi and Firmicutes were not influenced by nisin (P0.05), but were significantly reduced by monensin addition (P<0.05). Both nisin and monensin addition significantly increased the populations of sulfur-reducing bacteria and Clostridium aminophilum (P<0.05), but had no influence on the population of Clostridium sticklandii (P0.05). Conclusion: Appropriate nisin addition could reduce methanogenesis and ammoniagenesis, while had no adverse effect on feed digestion. These effects are probably associated with the variation of rumen functional microbial populations and communities.