THE ROLE OF DIET QUALITY AND ENERGY NEED IN THE NUTRITIONAL ECOLOGY OF A SMALL HERBIVORE, MICROTUS-OCHROGASTER

The objective of this study was to determine the effect of low-quality diets and increased energy needs on nutritional aspects of the prairie vole (Microtus ochrogaster). In the laboratory, high-fiber diets were correlated with higher rates of food intake and larger hindguts, as well as a lower digestibility of dry matter, cell solubles, energy, and nitrogen, but higher fiber digestibilities than low-fiber diets. Acclimation to cold temperatures resulted in higher rates of food intake than acclimation to warm temperatures. In addition, the size of the small intestine and cecum increased in response to cold acclimation. Although increases in intake, resulting from acclimation to cold temperatures, did not result in changes in the digestibility of the diet or dietary components, they did result in decreases in the dietary turnover time. Thus, increases in transit rate through the gut do not necessarily result in declines in the amount of energy extracted per gram of food ingested. More energy per unit time, however, can be extracted from the diet, perhaps because of increases in the size of the gut allowing maintenance of digestibilities and energy need in the face of higher transit times.