FOOD SORTING BY COLLARED LEMMINGS (DICROSTONYX GROENLANDICUS) AND PRAIRIE VOLES (MICROTUS-OCHROGASTER) - A CAUTIONARY NOTE FOR DIGESTIBILITY STUDIES

Small herbivores are often confronted with poor quality diets; in resp onse to this situation, they may sort their food to increase diet qual ity. Neutral detergent fiber (NDF) levels were measured in three pelle ted diets fed to collared lemmings (Dicrostonyx groenlandicus) and pra irie voles (Microtus ochrogaster) and compared to levels in orts colle cted from the same diets and animals. Lemmings sorted and discarded th e fibrous parts of food pellets on all three diets (17.3% to 25.9% hig her NDF in orts), whereas voles sorted out fibrous particles on only o ne diet Calculations of NDF digestibility were significantly reduced b y particle sorting (up to 16.9% decrease in digestibility). In reviewi ng the literature, we found that in more than half of studies examined , orts may not have been analyzed for these differences. Researchers m ust carefully consider such effects, especially when conducting digest ibility studies with herbivores on pelleted diets. Copyright (C) 1996 Elsevier Science Inc.