Effects of high-sulphur water on hepatic gene expression of steers fed fibre-based diets.

Sulphur-induced polioencephalomalacia (sPEM), a neurological disorder affecting ruminants, is frequently associated with the consumption of high-sulphur (S) water and subsequent poor performance. Currently, there is no economical method for S removal from surface water sources, and alternative water sources are typically neither readily available nor cost-effective. Determination of genes differentially expressed in response to high-S water consumption may provide a better understanding of the physiology corresponding to high dietary S and ultimately lead to the development of treatment and prevention strategies. The objective of this study was to determine changes in gene expression in the liver, an organ important for S metabolism, of fibre-fed steers consuming high-S water. For this study, liver tissues were collected on the final day of a trial from yearling steers randomly assigned to low-S water control (566mg/kg SO4; n=24), high-S water (3651mg/kg SO4; n=24) or high-S water plus clinoptilolite supplemented at either 2.5% (n=24) or 5.0% (n=24) of diet dry matter (DM). Microarray analyses on randomly selected healthy low-S control (n=4) and high-S (n=4; no clinoptilolite) steers using the Affymetrix GeneChip Bovine Genome Array revealed 488 genes upregulated (p<0.05) and 154 genes downregulated (p<0.05) in response to the high- vs. low-S water consumption. Real-time RT-PCR confirmed the upregulation (p<0.10) of seven genes involved in inflammatory response and immune functions. Changes in such genes suggest that ruminant animals administered high-S water may be undergoing an inflammation or immune response, even if signs of sPEM or compromised health are not readily observed. Further study of these, and other affected genes, may deliver new insights into the physiology underlying the response to high dietary S, ultimately leading to the development of treatments for high S-affected ruminant livestock.