Effects of Sulfur Sources on Ruminal S Bioavailability, Fermentation Activity and Microbial Populations Measured In Vitro
Abstract
The aim of this study was to better understand the ruminal solubility, bioavailability, effect on fermentation and microbiota of different sulfur (S) forms. In vitro fermentations with rumen fluid were conducted for 70hrs. Hay was incubated solely (CON), or with 0.5%DM of S, as: elemental sulfur (ES), Na2SO4 (NaS), (NH4)2SO4 (NHS) and MgSO4 (MgS). Fermentation was assessed by gas production (TGP) and dry-matter degradability (dDM%). Solubility and bioavailability were estimated by S concentration of the supernatant (SOL) and of bacteria (BACT). Microbial community was assessed by amplification of the 16SrRNA gene. NHS decreased (p<0.05), ES and NaS didn’t affect, while MgS increased (p<0.01) TGP. MgS increased (p<0.001), whilst ES, NaS and NHS showed no effect on dDM%. Sulfate sources increased (p<0.001), while ES did not affect the S content of SOL. S content of BACT suggests that sulfates have a high bioavailability, while ES is poorly assimilated by bacteria. Some variations of the microbial community were observed, including a lower abundance of methanogens with all S sources and a higher abundance of Desulfovibrio with MgS. These findings suggest that ES has limited solubility, whereas sulfates, particularly MgS, exhibit a high level of solubility in the rumen, resulting in a more effective utilization by bacteria.
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