The Effects of Negative- and Positive- Charged Surfactants on In vitro DM Digestibility and the Growth of Ruminal Mixed Microorganisms

Abstract

In order to investigate the effects of supplemental ionic surfactants in in vitro ruminal fermentation, N-Lauroylsarcosine sodium salt (N-LSS) and sodium dodecyl sulfate (SDS) for negative ( ) ionic surfactant, and hexadecylpyridinium chloride monohydrate (HPCM) and hexadecyltrimethyl ammonium bromide (HTAB) for positive (+) ionic surfactant were supplemented by 0.05% and 0.1% into the Dehority's artificial medium containing rice straw (1 mm) as a substrate. In vitro DM digestibility, the growth of rumen mixed microbes, pH, cumulative gas production and SEM (Scanning Electron Microscopy) observation of microbial attachment on rice straw particle were investigated through the experiment composing 9 treatments (two supplemental levels of two positive ionic (+) surfactant, two supplemental levels of two negative ( ) ionic surfactant) including the control. The sample collection was at 6, 12, 24, 48 and 72 h post fermentation with 3 replications per treatments. DM digestibility in treatments supplemented (+) or ( ) surfactants almost stopped afterward 12 h fermentation, in vitro DM digestibility at 72 h post fermentation in the ionic surfactants was at half level of that of the control (P<0.05). Accumulative gas production in in vitro was less (P<0.05) with addition of ionic surfactants compared to the control. The amount of rumen mixed microbes recovered from in vitro incubation fluid pleateaued at 12 h post fermentation for the positive (+) ionic surfactants, but steadily increased as fermentation time elapsed for the control. Rumen microbial growth rate was significantly (P<0.05) low in the negative ( ) ionic surfactant compared to the control. pH of the incubation fluid was ranged from 6.02 to 7.20, and was the highest in the negative ( ) ionic surfactants, and was the lowest in the control (P<0.05). In SEM observation, rumen microbial population attached on rice straw particle was less with addition of ionic surfactants than the control. In conclusion we could not found any positive effects of negative-and positive-charged surfactants on rumunal fermentation characteristics and rumen microbial growth rates.