Objectives: To describe the effects of an abrupt increase of concentrates in the diet of dairy cows on myoelectric activity of the spiral colon and on fermentation patterns in the rumen and large intestine.
Animals: 6 healthy lactating Simmental x Red-Holstein cows.
Procedures: The diet of 6 cows implanted with bipolar electrodes in the spiral colon was changed from hay only to a ration of 50% hay:50% starch-rich concentrates during a period of 60 hours. Myoelectric activity of the spiral colon, concentrations of absolute and undissociated volatile fatty acids (VFA), and pH of ruminal and large intestinal contents were monitored before, during, and after the dietary change.
Results: Significant changes in patterns of myoelectric activity of the spiral colon were restricted to phases III and IV of the bovine migrating myoelectric complex and to propagation velocity. Significant alterations were not observed in pH or VFA concentrations in ruminal fluid, but pH decreased and VFA concentrations increased significantly in fecal specimens after the change of diet.
Conclusions and clinical relevance: Although rumen fluid is of limited value for measurement of certain indicators of fermentation, fecal samples can be used for measurement of pH and VFA concentrations, which serve as indicators of fermentation patterns in the large intestine. Increased concentrations of VFA and low pH in large intestinal digesta have a minimal influence on myoelectric activity of the spiral colon. Increased luminal VFA concentrations are unlikely to play an important role in the etiopathogenesis of motility disorders of the large intestine in cattle.