title: Sulfur influences on rumen microorganisms in vitro and in sheep and calves.
abstract: When continuously cultured ruminal microbes were given orchardgrass hay and sufficient sulfuric acid or hydrochloric acid to maintain a pH of 5.5, fermentation and numbers of protozoa were reduced compared with cultures whose pH was controlled with phosphoric acid. Likewise, when sulfur-deficient, purified diets were supplied to cultures, less methane (mmol X liter-1 X d-1), 3.2 vs 32.6, was produced and fewer cellulolytic bacteria (log10/ml), 5.8 vs 7.2 were present than when cultures were given the same diet supplemented with .3% elemental sulfur. The rumen of sheep fed the .04% sulfur diet had reduced digesta weights (1.69 vs 3.2 kg) compared with sheep fed the diet with .34% sulfur at the same intake. There also was reduced methanogenesis 12.3 vs 25.8 mmol X liter-1 X d-1) and reduced numbers of cellulolytic bacteria (7.4 vs 8.4 log10/ml) in sulfur-deficient sheep in comparison to sulfur-supplemented sheep. In growing calves, the same types of bacteria predominated in the rumen, but more facultative anaerobic bacteria were isolated from calves fed .04% sulfur than from calves fed diets with .34 to 1.72% sulfur. None of the dietary levels of sulfur appeared toxic. Regardless of treatment, volatile fatty acids were more predominant than lactic acid as end-products of fermentation of ruminal microbes in fermenters, sheep and calves. The greater methanogenesis and the greater cellulolytic bacterial numbers of sulfur-supplemented sheep compared with sulfur-deficient in vitro cultures, is interpreted to be the result of recycling of sulfur to the rumen in sheep where it is efficiently scavengered by ruminal bacteria.
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000382:microbiology*; D005285:Fermentation; D006851:Hydrochloric Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D010756:Phosphoric Acids / Q000494:pharmacology; D012417:Rumen / Q000382:microbiology*; D012756:Sheep / Q000382:microbiology*; D013455:Sulfur / Q000172:deficiency / Q000494:pharmacology*; D013464:Sulfuric Acids / Q000494:pharmacology
chemical_list: D010756:Phosphoric Acids; D013464:Sulfuric Acids; D013455:Sulfur; D006851:Hydrochloric Acid