LIMITS TO FOOD-INTAKE AND FIBER UTILIZATION IN THE PRAIRIE VOLE, MICROTUS-OCHROGASTER - EFFECTS OF FOOD QUALITY AND ENERGY NEED

We fed prairie voles (Microtus ochrogaster) rat chow diluted with variable amounts of a-cellulose to determine 1) how much fiber the voles could tolerate in their diet; 2) changes in food intake and digestibility of dry matter and of fiber; 3) the extent to which voles utilized fiber as an energy source; and 4) whether any of these variables differed between groups of animals maintained at 5 or 22 degrees C. Fiber content of the diets ranged from 20 to 84%. Animals held at 5 degrees C maintained body mass through a diet containing 69% fiber, while animals held at 22 degrees C maintained body mass through the 84% fiber diet. Dry matter intake increased with fiber level from 9.3 to 15.0 g . day(-1) for animals at 5 degrees C and from 5.6 to 14.0 g . day(-1) for animals at 22 degrees C; intake on the highest fiber diet eaten by either group was not different. Dry matter digestibility decreased significantly as the fiber in the diets increased, but was not affected by temperature treatments. Digestible dry matter intake for each group remained constant regardless of diet quality, but on each diet digestible dry matter intake for animals at 5 degrees C was significantly higher than that of the animals held at 22 degrees C. Digestibility of the fiber portion of the ex perimental diets remained constant as food quality decreased, so the percent of daily energy need met by fiber utilization increased with higher food intake. On the lowest quality diet each group tolerated, fiber digestion provided approximately 42 and 68% of the energy needs of voles at 5 and 22 degrees C, respectively.