COX, Christian L.*; SECOR, Stephen M.; University of Alabama; University of Alabama: Determinants of energy efficiencies for juvenile Burmese pythons, Python molurus
The relative proportion of ingested energy that is absorbed by the gut (digestive efficiency), becomes available for metabolism (assimilation efficiency), and is used for growth (production efficiency) varies with respect to meal type and in some cases with body temperature. To explore the effects of meal size and genetics on these three energy efficiencies, we fed sibling juvenile Burmese pythons (Python molurus) rodent meals equaling 15%, 25%, and 35% of body mass and individuals from five different clutches 25% size rodent meals. For each of 12 consecutive feeding trials, body mass was recorded and feces and urate of each snake was collected. Energy content of meals (mice and rats), feces, urate, and pythons were determined by bomb calorimetry. Apparent digestive efficiency was calculated as (energy consumed – fecal energy)/energy consumed, apparent assimilation efficiency as (energy consumed – fecal and urate energy)/energy consumed, and production efficiency as energy of body growth/energy consumed. For siblings fed three different size meals, growth rate increased with larger meals, but there was no significant variation among meal size for any of the calculated energy efficiencies. Among the three size meals, apparent digestive, apparent assimilation, and digestive efficiencies averaged 90.6%, 84.1%, and 39.7%, respectively. In contrast, there was significant variation for each of these energy efficiencies among the five different clutches ingesting meals 25% of body mass. Among these five clutches there was a significant negative correlation between mean standard metabolic rate (SMR) and production efficiency. Clutches that tended to have lower SMR were therefore able to allocate more of ingested energy into growth.