Review: Genomics of subacute ruminal acidosis
The present review will present the most recent development in sub-acute ruminal acidosis (SARA) regarding high concentrate diet and its interaction on gene expression. The SARA is a common disorder in high producing ruminants. In addition SARA is a big challenge for ruminant nutritionists, therefore, the subject has been extensively studied in recent decades. In current decade nutrigenomic has been used to understand the cellular response influenced by high concentrate diet in ruminants. For sustainability of higher growth and production, animals are force to feed on high concentrate and low fiber in diet. High concentrate diet leads to accumulation of higher concentration of VFA consequently ruminal pH decreases. Depression in pH for longer duration impaired ruminal epithelium tight junctions and hyperkeratosis. SARA is
characterized by fewer tight junctions between cells, thinner cell layers, and an increased
sloughing of the stratum corneum leading to a weakened permeability barrier. Ruminal epithelium serves as barrier for microbes, damages to ruminal epithelium leads to translocation of lipopolysaccharides (LPS) from compromised ruminal epithelium to blood circulation and different organs of the body. The LPS induce immunogenic response in ruminal papillae, epithelium, liver, and other organs. LPS induce a cascade mechanism of gene expression by binding with Toll-like receptor 4 (TLR4) a receptor for LPS, binding of LPS with TLR4 activate nuclear factor kappa B (NF-kB) consequently genes for interleukin 6 (IL), IL-8, tumor necrosis factor (TNF)-α and many more genes were up regulated or down regulated in rumen epithelium and other organs. In conclusion feeding high concentrate diets to ruminants’ triggered local and systemic inflammation response at molecular level. By exploring the mechanism of SARA and its effects on gene up regulation or down regulation can be a value able tools for understanding the SARA and its adverse effects on animal health and production performance.