Intracellular pH regulation of ruminal epithelium and its impacts on rumen acidosis

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The objective the proposed research is to evaluate the single nucleotide polymorphism (SNP) in genes coding proteins involved in intracellular pH regulation and its impacts on regulation of rumen pH. Rumen acidosis is the metabolic disorder that negatively affects health and productivity of ruminants. Feeding high grain diets often causes excess fermentation and results in accumulation of fermentation acids in the rumen, leading to feed intake reduction, liver abscesses, lameness, and milk fat depression. However, a significant variation exists among animals in the extent of tolerance to a highly fermentable diet; some easily experience ruminal acidosis while others improve productivity with little symptom of ruminal acidosis. Therefore, it is extremely important to identify factors that make animals more tolerant to ruminal acidosis. Based on findings from previous research, genes coding transport protein involved in intracellular pH regulation in ruminal epithelia such as NHE3 and MCT1 are initial targets for SNP discovery, and it will be performed through sequencing analyses, in which potential SNP will be identified by comparing genomic sequences amplified using primers designed based on reported genomic sequences or cDNA sequences of the target genes. The SNP genotype and allele frequencies will be compared between the acidosis-susceptible and acidosis-resistant animal groups using a Chi-square test, and significant difference of SNP genotype and/or allele frequencies will indicate a putative association between the gene SNP and resistance to rumen acidosis. The SNP that shows significant difference of genotype and/or allele frequencies between the acidosis-susceptible and acidosis-resistant animal groups will be genotyped for a greater number of animals. The proposed project is expected to provide novel molecular approaches to improve animal health and production efficiency. Marker-assisted selection for acidosis resistance and nutritional management considering animal genetics are expected to contribute to sustainable dairy production in Canada by mitigating ruminal acidosis problems.