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 O55：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.
Relationships among maternal nutritional status before calving, gestation period and calf size were investigated in Japanese Black cattle. The study included a total of 55 cows that calved between 2010 and 2011. Based on the average pregnancy period of Japanese Black cows（285 days）, the study animals were divided into two groups: 14 cows that calved within this period（Group 1）and 41 cows that calved after due date（Group 2）. The mean change in heart girth from 2 weeks before calving to the day of calving or calving due date was significantly greater in Group 1（0.36 ± 3.79 cm）than in Group 2（-0.71 ± 4.00 cm on due date and -2.27 ± 4.00 cm on calving date）indicating poorer nutritional status in cows that had delayed parturition. The sex ratio of calves, calving season and age of the cows, which have been shown to affect gestation period, were similar between the two groups. When two farms with two different feeding programs were compared, the mean change in heart girth was significantly lower in the farm having poorer nutritional adequacy than in the other farm with better nutritional adequacy. The former farm also had a significantly longer gestation period compared to the other farm. These results suggest that suboptimal nutritional status during pregnancy was one of the causes of delayed calving. In the study groups, the head circumference of calves at birth increased and was significantly correlated with the gestation length, whereas the birth weight of calves was not associated with the gestation length. Together, the results of our study suggest that the poor nutritional status of cows in the prenatal period can lead to delayed calving and a larger calf head. Good nutritional management of pregnant cows plays a key role in preventing delayed calving associated with large calf head.
A 6-month-old Holstein heifer presented with hindlimb paralysis and astasia. Spinal injury was suspected from the spinal curvature and swelling from T13 to L2. Abdominal ultrasound examination revealed a mass of 8 cm in diameter near the right kidney. Ultrasound-guided needle aspiration of the mass revealed pus containing Gram-positive cocci, and paravertebral body abscess was strongly suspected. Computed tomography examination revealed a vertebral fracture of L2. At necropsy, two abscesses were found on both sides of the spine from L1 to L5. These abscesses were fused near the vertebral body of L1 and L2 encapsulating the vertebral body. A pathologic fracture of L2 was confirmed, and a part of the bone was compressing the spinal cord.