Browsing by Subject "Hydrogen sulfide"
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Item Effect of yeast, protected minerals and bismuth subsalicylate on in vitro fermentation by rumen microbes.(2012-04) Moreno, Martín RuizThree experiments were conducted using a dual flow continuous culture fermenter system. In Experiment I, two levels of active dry yeast at 0 or 2 mg/fermenter/day (NY and YS, respectively) were infused twice daily to fermenters in a completely randomized arrangement of treatments. Apparent and true OM digestion was not affected by yeast. No differences were obtained in NDF and ADF digestion. Total VFA concentrations were not affected by treatments. Addition of yeast did not affect VFA molar proportions or estimated CH4S production but resulted in a trend for a lower A:P ratio. Addition of yeast decreased NH3-N concentration and NH3-N daily flow, without affecting crude protein digestion and efficiency of microbial protein synthesis. Mean and minimum pH of fermenters did not differ between treatments but a trend for a lower maximum pH was obtained with yeast. In conclusion, a low dose of active dry yeast decreased NH3-N concentration and daily flow, without affecting any other of the in vitro rumen fermentation characteristics measured in this study. In Experiment II, effects of two levels of lignosulfonate and two sources of minerals (protected and unprotected) on rumen fermentation were evaluated using a 2 x 2 factorial arrangement of treatments. Addition of lignosulfonate tended to decrease daily flow of non NH3-N, efficiency of microbial protein synthesis, total VFA concentration and molar proportion of acetate, but increased molar proportion of propionate, valerate and caproate. Protected minerals decreased molar proportion of propionate. Addition of lignosulfonate increased ruminally soluble Cu and Mn, whereas protected minerals reduced ruminally soluble Cu. Concentrations of bacterial Cu and Zn increased with protected minerals in absence of lignosulfonate. Concentration of Mn was not affected by treatments. Addition of lignosulfonate resulted in higher enzymatic release of Zn from solids outflow but lower from bacterial pellets. Mean, minimum and maximum fermentation pH was higher with lignosulfonate, and not affected by mineral source. Addition of lignosulfonate induced major changes in ruminal fermentation. Protection of minerals decreased rumen soluble Cu and increased bacterial Cu and Zn without affecting postruminal release of minerals. In Experiment III, addition of bismuth subsalicylate (BSS) at 1% of DM and monensin (MON; 5 ppm) were used to assess their effects on rumen metabolism and H2S release by rumen microbes in a 2 x 2 factorial arrangement of treatments. Addition of BSS increased digestion of OM, NDF and ADF but decreased that of NFC and total VFA concentrations. Molar proportions of acetate and propionate increased with BSS in the diet, while that of butyrate decreased. Monensin decreased ADF digestion and A:P ratio, without affecting molar proportions of major VFA. Regarding nitrogen metabolism, MON increased non NH3-N outflow without affecting other measurements. Addition of BSS to the diet increased NH3-N concentration, NH3-N flow and dietary-N flow, while decreasing microbial-N outflow, CP digestion, and efficiency of microbial protein synthesis. Headspace H2S was reduced by 99% with BSS treatment but was not affected by MON. Only minor changes in fermentation pH were found with MON, but an increase in mean, minimum and maximum fermentation pH were found following addition of BSS. Results indicate that BSS can markedly reduce H2S production in short term and long term in vitro rumen incubations.Item Effects of dietary roughage and sulfur in diets containing corn dried distillers grains with solubles on hydrogen sulfide production and rumen fermentation by rumen microbes in continuous and batch culture(2014-04) Binversie, Elizabeth Y.Dried distillers grains with solubles (DDGS) is an inexpensive feed alternative to corn. Previously, over-inclusion of DDGS has produced toxic concentrations of ruminal hydrogen sulfide (H2S) gas, resulting in polioencephalomalacia (PEM), a degenerative brain disease. Production of ruminal H2S requires an acidic environment conducive to converting free sulfur to H2S in the rumen. Therefore, it was hypothesized that creating a less acidic rumen environment would help mitigate ruminal H2S production. Two experiments were conducted to determine the effects of dietary roughage and sulfur on in vitro fermentation with ruminal microbes in continuous culture and batch culture. Six dietary treatments were formulated that paired 3 concentrations of sulfur (0.3, 0.4 and 0.5% of diet DM) with 2 concentrations of roughage (3 and 9% of diet DM) and are as follows: low roughage low sulfur (LRLS), low roughage moderate sulfur (LRMS), low roughage high sulfur (LRHS), moderate roughage low sulfur (MRLS), moderate roughage moderate sulfur (MRMS) and moderate roughage high sulfur (MRHS). A diet comprised of 0% DDGS was used as the control (CON) diet. Roughage had no effect on H2S production but it did increase fermenter pH, creating a less acidic environment. In experiment 2, an increase in dietary sulfur caused an increase in total H2S production, but there was no direct effect of roughage on total H2S production. Higher dietary roughage created a less acidic pH but at the expense of in vitro fermentation, because of the lower total VFA concentration. Further investigation is needed to determine more effective methods of mitigating H2S production using dietary manipulation, such as higher inclusion of dietary roughage or use of different roughage sources.Item Electrochemical Removal of Aqueous Sulfide from Swine Manure(2018-06) Wang, YuchuanHydrogen sulfide (H_2 S) produced in swine manure pit storage is a safety hazard to both human and animals. An electrochemical treatment based on low carbon steel electrodes was developed to reduce aqueous sulfide and emitted H_2 S concentration from manure storage. At the selected condition (Applied voltage = 0.7 V, immersed electrode surface area = 19 cm^2/L, initial sulfide concentration = 5 - 6 mM, operation temperature = 19 °C), the process achieved an average sulfide removal rate of 2.60 mg S^(2-)/(cm^2⋅day) for the zero order kinetic model, and a rate coefficient of 0.275 /day for the 1st order kinetic model. Constant disturbance created to simulate the pumping event was found greatly accelerated the H_2 S release directly from the manure liquid; however, removals of over 90% sulfide and H_2 S significantly reduced the risk. Methane concentration went higher as the sulfide removal; 46% higher concentration was found at 95% sulfide removal from the initial concentration over 6 mM. Different from the electrochemical sulfide removal from less viscous wastewater, low voltage applied in this study was proved feasible to maximize the precipitation and minimize the flotation in swine manure. The installation of this technology may reduce the risk of manure pump-out in terms of H_2 S over-exposure and may be applied in similar circumstances where H_2 S poses threats to health and life.