Milk intake and carbon dioxide production of piglets determined with the doubly labelled water technique

The present study was undertaken to study different methodological aspects of quantifying CO(2) production and milk intake of suckling piglets using the doubly labelled water (DLW) technique. In total, 37 piglets were enriched intraperitoneally with DLW to study equilibration time of (18)O (n = 3), to validate the estimation of milk intake and CO(2) production (n = 10) of piglets fed milk replacer and to quantify milk intake and CO(2) production of piglets nursed ordinarily by sows (n = 24). Enrichment of (18)O in expired air was analysed without any sample preparation, whereas enrichment of (18)O in serum was analysed after a minimum step of sample preparation, which included pipetting of the sample, blowing gaseous CO(2) into the vial for 3s and equilibrating for 24 h. The (18)O enrichment of CO(2) in expired air was constant within 30-40 min of intraperitoneal injection, suggesting that DLW was equilibrated within the body water by that time. For piglets fed milk replacer the estimation of the daily CO(2) production by the DLW method (64.0 +/- 2.71 CO(2/)day) was in agreement with that obtained by respiration trials (64.7 +/- 1.81 CO(2)/day). Furthermore, the intake of milk replacer (891 63 g/day) determined by deuterium oxide (D(2)O) dilution was similar in magnitude to that found by weighing the milk disappearance (910 +/- 58 g/day). The milk intake of piglets fed milk replacer was comparable with that of sucking piglets, but sucking piglets had a remarkably higher CO(2) production than artificially reared piglets, which likely was caused by a higher intake of milk solids and a higher activity level. For sucking piglets, the daily CO(2) production increased curvilinearly with increasing live weight (LW) in kg: piglet CO(2) production (1/day) = 25.75 X LW -1.01 X LW(2). In conclusion, (18)O equilibrates fast within the body water pool when administered intraperitoneally, and the accuracy of assessing milk intake and rate of CO(2) production using the DLW technique is promising. Assessment of excess enrichment of (18)O in serum proved to be robust Finally, the CO(2) production of piglets fed milk replacer differs considerably from that of sucking piglets.