Digestibility of Common Forage Plants and Energetic Requirements of the Black-Tailed Prairie Dog

Abstract

Black-tailed prairie dogs (Cynomys ludovicianus) assimilated 51.5 percent of the wheatgrass (Agropyron intermedium) they consumed; thus, they would have to consume 0.148 kcal · g-1 · day-l in order to obtain the 0.076 kcal · g-1 · day-1 they would require to maintain their weight. Prairie dogs assimilated 31.5 percent of the buffalograss/blue grama mixture (Buchloe dactyloides/Bouteloua gracilis) they were fed. They would have to consume 0.229 kcal · g-1 · day-1 of this forage to assimilate 0.072 kcal · g-1 · day-1 and maintain their weight. The proximate composition of forages fed in feeding trials was similar to that found for those collected on the study area. Total digestible nutrients (TON) for wheatgrass in feeding trials and from the study site averaged 46.7 percent and 45.5 percent, respectively. The mean TON for buffalograss/blue grama feeding trial and study area forages were 26.4 percent and 23 percent, respectively. The assimilation efficiency (AE) of prairie dogs on their natural diet of 34 percent forbs and 65 percent grasses was 71.8 percent. The higher AE in the wild population than in captive animals fed grasses is due to the presence of highly digestible forbs. The estimated Resting Metabolic Rate (RMR) of 0.056 kcal · g-1 day-l is relatively low; 85 percent of the Basal Metabolic Rate as predicted by a metabolic body size formula. The energy cost of activity is the primary cause for the difference in RMR estimates from oxygen consumption tests and caloric requirements found in feeding trials. The prairie dog feeding trial results were 1.32 times greater than the RMR estimates