Abstract:
Proc. Aust. Soc. Anim. Prod. Vol. 18 NEW METHODS FOR THE MEASUREMENT OF ENERGY EXPENDITURE J.M. LUSH,* J.M. GOODEN* and E.F. ANNISON* Energy expenditure in animals may be calculated from their oxygen consumption An alternative procedure to measuring OC in a respiration chamber is to use the Fick principle to calculate the OC of the whole animal from cardiac output and the difference in the concentration of oxygen in blood across the This approach has been greatly facilitated by new methodology for the lungs. measurement of blood flow based on ultrasonics (Transonics Inc., Cornell, USA), which permits continuous measurement of cardiac output by monitoring blood flow in the aorta. Direct comparison of gas-exchange data derived by blood analysis with those generated by the use of the conventional head-box showed good agreement between the two methods in the pig (Giles et al. 1989). (=I l The blood flow probe has also expanded the application of the Fick principle In measurements of the oxygen consumption (Webster 1974) to defined tissues. by the portal drained viscera (PDV) of sheep, six Merino wethers (4 years old, average weight 44 kg) were surgically prepared with chronic indwelling A blood flow probe catheters in the portal vein (P) and femoral artery (A). (Transonics Inc., Cornell, USA) was placed around the portal vein to measure The sheep were fed continuously a pelleted diet of portal blood flow (PBF). 60% lucerne chaff and 40% oat grain at each of two levels, 4.02 and 8.04 MJ of Blood was sampled from ME per day (0.75X and 1.50X maintenance respectively). P and A. OC of the gut was calculated by multiplying PBF by the difference in oxygen content between A and P. The aerobic metabolic rate (Ma) of the PDV was calculated (Webster et al, (1975). Table 1 Aerobic metabolic rate of the portal drained viscera of sheep PBF, OC and Ma were significantly higher at an intake of 8.04 MJ/day (Table 1). Values for M are of the same order of those obtained by Webster (1979) who suggested thlt at maintenance M is about 90 kJ/kg'*'/day. The ultrasonic blood flow probe which providesaan instantaneous and continuous mesurement of energy expenditure, with minimum response time, may be applied to defined tissues in vivo, and to the whole animal. GILES, L-R., GOODEN, J-M., BLACK, J-L., ANNISON, E.F. and TUCKER, R.J. (1989). Proc. Nutr. Soc. 14. (in press). WEBSTER, A.J.F. (1974). Proc. Nutr. Soc. 33: 155. WEBSTER, A.J.F., OSUJI, P-O., WHITE, F. and INGRAM, J-F. (1975). Br. J. Nutr. 34: 125. WEBSTER, A.J.F. (1979). In 'Digestive Physiology and Metabolism in Ruminants' ,Proc 5th Int. Symp. on Ruminant Physiology, p. 469, editors, Y. Ruckebusch and P. Thivend. (MTP Press Ltd.: England). * Dept of Animal Husbandry, University of Sydney, Camden, N.S.W. 2570, 515