Effect of endotoxemia on rumen motility, abomasal motility and liver function in cattle

The present study investigated the effect of endotoxemia on rumen motility, abomasal motility and liver function in cattle. In Chapter 1, a high-concentrate diet with an increased percentage of rolled barley was introduced to healthy Holstein cows. All cows developed subacute ruminal acidosis (SARA). The ruminal free lipopolysaccharide (LPS) level increased during SARA by about 4-fold on Day 1 and about 23-fold on Day 14 of administration. The serum LPS concentration was below the detection limit of assay before administration but increased to 3.8±5.2 pg/ml on Day 1, reaching 12.7±8.6 pg/ml on Day 5. The amplitude of rumen motility significantly decreased to 70±10% on Day 2, and all cows developed ruminal tympany. The rumen contraction amplitude further decreased to 52±2% on Day 14. The amplitude of abomasal motility significantly decreased to 60±8% on Day 2. In the liver tissue, focal necrosis was observed on Day 14, and small areas of hemorrhage were observed on Day 28. In Chapter 2, the association between ruminal parakeratosis and LPS translocation was investigated. Ruminal acidosis was induced in 5 Holstein steers by grain over-feeding. Three steers developed ruminal parakeratosis, while the remaining 2 steers maintained the normal ruminal lining. In the 3 steers with ruminal parakeratosis, LPS was detected in the peripheral blood, and focal necrosis was noted in the liver tissue. In the 2 steers without ruminal parakeratosis, on the other hand, LPS was not detected in the peripheral blood, and no abnormalities were observed in the liver tissue. These results suggest that ruminal parakeratosis has led to the translocation of free LPS from the rumen into the systemic circulation. In Chapter 3, healthy Holstein steers received intravenous infusion of LPS (Escherichia coli 055:B5), and its effects on rumen motility, abomasal motility and liver function were investigated. Rumen and abomasal motility ceased at 1 hour after LPS infusion. At 9 hours after the infusion of LPS, LPS became undetectable in the peripheral blood, and the rumen and abomasal motility was restored. After 7 days of administration, focal necrosis was observed in the liver tissue. These results suggest that several findings of SARA in cattle, including ruminal and abomasal atony and impairment of liver function, are likely associated with the translocation of free LPS from the rumen into the systemic circulation.