Effects of various compounds on in vitro ruminal fermentation and production of sulfide

We evaluated the effect of several compounds on their ability to reduce the production of sulfide in in vitro ruminal fermentations, when sulfur content of the diet was 1% (dry matter basis). Excess sulfur increased (p<0.05) ruminal sulfide production, but had no effects on VFA production. The effect of 1, 10 and 25 ppm (fluid basis) of 9,10 anthraquinone (AQ) and molybdenum in high sulfur diets was also studied. Specifically, AQ (10 ppm) and molybdenum (25 ppm) reduced (p<0.05) hydrogen sulfide production by 71 and 77%, respectively. The addition of AQ, but not molybdenum, decreased (p<0.05) the molar percentage of acetate and decreased methane production. The former compound also increased (p<0.05) the molar proportions of propionate, butyrate, and valerate. Bacitracin (1.25 ppm), oxytetracycline (1.25 ppm), chlortetracycline (5 ppm), lasalocid (5 ppm), bambermycin (0.3 ppm), monensin (5 ppm), and avoparcin (5 ppm) were tested relative to AQ (10 ppm) for their ability to affect sulfide production. Only chlortetracycline and oxytetracycline reduced (p<0.05) sulfide production, but they were less effective than AQ. Surprisingly, sulfide production was increased (p<0.05) by >50% when cultures were treated with monensin. Interactions between methanogens and sulfate-reducing organisms may be responsible for this finding. Several compounds have the ability to reduce ruminal sulfide production without negative effects on ruminal fermentation.