High Sulfate Water Affects Volatile Fatty Acid Profiles in Lambs

The semi-arid rangelands of the western United States often lack the water quality needed to support the health and performance of livestock. In times of drought, sulfate (SO₄^2-) can accumulate in the water supply. Certain rumen microbes responsible for converting feedstuffs into volatile fatty acids (VFA) for energy use by the host also reduce SO₄^2- to sulfide, resulting in H₂S accumulation and subsequent loss of livestock performance.  Our objective was to measure the effects of high- SO₄^2- water on rumen microbial populations and corresponding VFA concentrations in growing lambs.  Hampshire/Hampshire-cross ewe lambs (n = 12; initial BW 75.52 14.4 kg) were randomly allotted to individual pens and provided a forage-based, pelleted diet ad libitum. Lambs were offered high- SO₄^2- drinking water (3,000  500 mg SO₄/L) for 28 d followed by low- SO₄^2- (35 mg SO₄/L) drinking water for 7 d.   Rumen samples collected on d 0, 7, 28, and 35 were analyzed for VFA concentrations by gas chromatography, as well as for microbial taxa identification via DNA sequencing.  Acetate, propionate, isovalerate and valerate were affected (P < 0.05) by the SO₄^2- water treatment. Furthermore, abundances of Prevotella ruminicola, Selenomonas ruminantium, and Oscillibacter valericigenes, which produce propionate or acetate as end products of metabolism, were altered (P < 0.05) by the SO₄^2- water.  We conclude high- SO₄^2- drinking water changes the abundance of several rumen microbial species, possibly driving a shift in VFA production which could result in reduced host performance.