Since these gases are belched away, the animal would lose most of its energy. Nature has prevented the problem of acetate conversion to gas by making sure that retention time is never too long and is short enough to wash Methanosarcina out of the rumen. T he problem with dinosaurs having a traditional rumen is their very large body size. The largest plant-eating dinosaurs weighed more than 25 tons. Based on the observation that feed retention time in the rumen and body size appear to be a linear function, the retention time of a dinosaur rumen could be greater than 1,250 hours, a time clearly not compatible with efficient acetate utilization.
Some large herbivores have a different strategy for digesting plants.
The cecum is an enlarged pouch that extends from the intestines, and it too can serve as a habitat for microorganisms. Cecal fermenters do not retain feed as long as or digest plant materials as completely as ruminants, but this may not have been a problem for dinosaurs. Large plant-eating mammals had not yet evolved, and plants may have been more digestible. James Russell is a research microbiologist with the USDA Plant, Soil and Nutrition Laboratory. Archive Contents Copyright 1996, Contact MooMilk Produced by ISYS Idea Systems, Inc.