Altered rumen microbial populations in response to high sulfate water in lambs

Abstract Text:

Water is involved directly or indirectly in essentially every bodily process.  Therefore, access to quality water sources is critical for livestock wellbeing. In the western U.S., however, high sulfate (SO₄^2-) water sources are frequently encountered. High SO₄^2- water can cause overproduction of ruminal H₂S and result in compromised health and performance of the host. An initial trial (Trial 1) was conducted to determine the impact of high SO₄^2- drinking water on the rumen microbiome of growing lambs. A follow-up trial (Trial 2) then sought to confirm rumen microbial species involved in the response to high SO₄^2- drinking water and additionally identify species that adapt to SO₄^2- challenges. Each trial consisted of individually penned Hampshire-cross lambs (n = 43 in Trial 1; n=16 in Trial 2) which had access to ad libitum feed and high SO₄^2- water (3,000 mg SO₄^2-/L) for a 28 d period. Trial 2 also included a 7 d post-treatment period to obtain recovery data for later analysis. DNA was extracted and sequenced from d 0, 7, and 28 rumen samples and then compared with known 16S rDNA reads for microbial identification. Operational taxonomic units (OTU) were defined as sequence clusters with ≥ 97% identity and analyzed for the fixed effect of sampling day using the GENMOD procedure of SAS. Trial 1 resulted in a total of 145 OTU found in at least 1 of the 24 sequenced samples (8 lambs; 3 sampling dates); 8 OTU were affected (P ≤ 0.05) by sampling day. Trial 2 resulted in 287 OTU identified in at least 1 of the 24 sequenced samples (8 lambs; 3 sampling dates), with sampling day affecting (P ≤ 0.05) 38 of those OTU. Collectively, these results indicate a shift in rumen microbe relative abundance in response to high SO₄^2- water. Abundance variation may confer differences in host animal ability to tolerate and adapt to high SO₄^2- water. Similarities in microbial abundance changes across the two trials suggest that particular species are especially reactive to high ruminal SO₄^2- and are likely important to host response. Furthermore, certain microbial species demonstrated greater potential to adapt over time to a high SO₄^2- environment. Greater understanding of the rumen microbes involved in the response to high SO₄^2- drinking water is necessary for development of effective treatment and prevention strategies for ruminant livestock maintained in high SO₄^2- water regions. 

Keywords: DNA sequencing, microbes, rumen, sheep, sulfate