DEVELOPMENT OF A MOBILE, OPEN-CIRCUIT INDIRECT CALORIMETRY SYSTEM

A system for the rapid determination Of O2 consumption, CO2 production and subsequent indirect estimation of energy metabolism of ruminants has been updated and validated. The accurate determination of gas temp erature, relative humidity, absolute pressure and flow is important to the overall use of the system. Analogue outputs from the specific ana lyzers were multiplexed and then routed to a data acquisition system w ith appropriate software control. Subsequent data processing included modification to fit LOTUS 1-2-3 files. The analyzers were calibrated w ith standard test gases for the gas meters. In an experimental confirm ation trial, eight sheep were fed at maintenance (M) or 2 x maintenanc e (2M) or fasted 48 h after each level of intake (MF and 2MF, respecti vely) and subsequent energy metabolism was determined. Oxygen consumpt ion (mL min-1), metabolic rate (W) and CO2 production (mL min-1) were greater (P < 0.05) for animals fed 2M (111.2, 379.5 and 101.9, respect ively) than for those fed M (85.4, 291.2 and 86.1, respectively). Main tenance values were, in turn, also higher (P < 0.05) than those for ei ther MF (56.7, 193.4 and 48.0, respectively) or 2MF (54.6, 186.4 and 4 6.3, respectively). M sheep had a higher respiratory quotient (1.03) ( P < 0.05) than either MF sheep (0.86) or 2MF sheep (0.89), with 2M she ep being intermediate (0.95). There were no differences (P > 0.05) bet ween the two fasted states for all parameters. Results from the confir mation experiment agree with previously published work and were consis tent with those from similar systems.