Validation of Deuterium Oxide Method for Estimating Milk Intake By Piglets

The objective of the study was to validate the deuterium oxide (D₂O) dilution technique to estimate milk intake in nursing piglets. Eight 3-day old piglets were surgically fitted with a carotid catheter. Piglets were individually housed in cages (0.61 x 0.61 m) and fed milk replacer daily at 0700, 1100, 1500, 1900 and 2300. On day 7, blood and saliva samples were taken at 0800 and D₂O (1 mL/kg BW) was administered intra-peritoneally at 0900. Additional blood and saliva samples were collected at 1000 and 1100, and at 24, 48, and 72 h following the 1100 feeding on d 7. Piglets were weighed daily to adjust the volume of milk needed to meet minimum nutrient requirements. Saliva was harvested from all pigs using cotton gauze at the same time as for blood sampling. Two different approaches were used to estimate milk intake. One approach was based on piglet body composition and weight change (Abody), and the other approach was based on milk replacer composition and intake (Amilk). Data was analyzed using mixed model, with approach, sample, and day as fixed effects and piglet as random effect. Estimated daily milk intake (g) from D₂O (EMI) did not differ between Abody and Amilk when derived from either plasma (473 ± 53 and 458 ± 53, respectively) or saliva (619 ± 52 and 613 ± 52, respectively). On d 1, daily EMI based on plasma (560 ± 57) and saliva (583 ± 55) were greater (P < 0.01) than the actual milk intake (AMI) (442 ± 28). On d 2 and 3, EMI based on plasma were lower (P < 0.01) than AMI (403 ± 57 vs. 527 ± 28, and 433 ± 57 vs. 569 ± 28, respectively). Compared to AMI, EMI based on saliva did not differ on d 2 (596 ± 55 vs. 527 ± 28) and was higher (P < 0.05) on d 3 (669 ± 55 vs. 572 ± 28). Overall, EMI from plasma (465 ± 49) and saliva (616 ± 49) differed (P < 0.01). The EMI from saliva samples (616 ± 49) differed (P < 0.01) from AMI (513 ± 28). Results indicate that D₂O dilution approach requires additional validation studies before it can be used to accurately estimate actual milk intake.

Key Words: Milk Intake, Validation, Deuterium Oxide, Dilution, Piglets