Effect of High Sulfate Water on Rumen Microbial Populations in Lambs

Rumen microbes are responsible for the degradation of feedstuffs and certain species are capable of reducing dietary sulfur (SO₄^2-).  As a result, the host ruminant can be subject to health complications associated with the overproduction of H₂S by the SO₄^2- reducing bacteria. Our objective was to identify rumen microbial species that react and potentially adapt to high SO₄^2- drinking water. Hampshire and Hampshire-cross lambs (n = 12; initial BW 75.52 ± 14.4kg) were individually fed a forage-based pelleted diet for a 35 d period. High SO₄^2- drinking water (3,000 ± 500 mg SO₄^2-/L) was administered ad libitum for a 28 d period, followed by 7 d of low SO₄^2- (35 mg SO₄^2-/L) drinking water.  Rumen fluid collected via oral lavage on d 0, 7, 28, and 35, was extracted for DNA sequencing to identify microbial taxa. Paired-end reads were filtered, quality-trimmed, and compared with a known database of 16S rDNA reads.  Operational taxonomic units (OTU) were defined as sequence clusters with ≥ 97% identity and analyzed for fixed effect of sampling day with total OTU used as a covariate. A total of 287 OTUs were identified in at least 1 of the 32 total samples that were sequenced (8 lambs; 4 sampling dates). Of those, 39 were affected (P < 0.05) by sampling day. Results indicate a shift in ruminal microbial populations in response to high SO₄^2- water. Certain prevalent rumen microbial genera, such as Prevotella, Methanobrevibacter, Butyrivibrio, and Selenomonas, showed evidence of adapting to high SO₄^2- water.