Digestive physiology, resting metabolism and methane production of captive Indian crested porcupine (Hystrix indica)

Abstract

Limited physiological measurements exist for the digestive physiology of porcupines. We measured CH4 emission in three captive Indian crested porcupines (Hystrix indica; 16.1 ± 2.7 kg) fed a diet of pelleted lucerne, and measured feed intake, digestibility, and digesta mean retention time (MRT) of a solute and three particle markers (<2, 10 and 20 mm). Marker excretion patterns suggested secondary peaks indicative of caecotrophy, with MRTs of 26.4 h for the solute and 31.5, 26.8 and 26.2 h for the three particle markers, respectively. At a dry matter intake of 58 ±10 g/kg body mass0.75/day, porcupines digested 49 and 35% organic matter and neutral detergent fibre, respectively, which is in the lower range of that expected for horses on a similar diet. The respiratory quotient (CO2/O2) was 0.91, the resting metabolic rate 274 kJ/kg body mass0.75/day, and CH4 emissions averaged at 8.16 l/day and 17.9 l/kg dry matter intake. Accordingly, CH4 yield was so high that it resembled that of a hypothetical ruminant of this body mass. The results are in accord with general understanding of hystricomorph rodent digestive physiology, and support recent findings that CH4 production may be more prominent in rodents than previously thought.