Effects of different sources and levels of dietary iron and selenium on the postprandial net portal appearance of these minerals in pigs

This study compares the post-absorptive levels of iron (Fe) and selenium (Se) in pigs fed different sources and levels of these minerals. Twelve 55-kg pigs were surgically equipped with portal and carotid catheters and a portal ultrasonic flow probe and used in a cross-over design to assess the 11-hours net portal-drained viscera (PDV) flux of serum Fe and Se after ingestion of boluses containing adequate (A; 200 and 0.6 mg) or high (H; 400 and 1.2 mg) levels of these minerals from dietary inorganic (I) or organic (O) sources. Arterial Fe concentrations increased (158 %) within the first six hours post-meal and gradually decreased thereafter (P < 0.01). Values for I were greater than O until six hours post-meal (P < 0.01) and for A than H between five and eight hours post-meal (P ≤ 0.01). There was a tendency for the interaction source x level (P = 0.07) on net PDV fluxes of Fe where values for AI were greater than AO (P = 0.02). The cumulative Fe PDV appearance (% of intake) was greater for I (2.2 %) than O (-1.7 %) after four hours post-meal (P = 0.02) but this effect was no longer detected at 11 hours post-meal. Arterial Se concentrations decreased by 7 % from pre-meal values until 11 hours post-meal (P < 0.01) and this decline was more pronounced for O than I (P = 0.03). Net PDV flux of Se was positive but only during the first 90 minutes post-meal (P < 0.01). The cumulative Se PDV appearance (% of intake) was greater for I (20.0 %) than O (-3.8 %) at 45 minutes post-meal (P = 0.04) but this effect did not persist thereafter. In conclusion, net availability of Fe and Se was greater for I than O during the early post-meal period. Whether these results reflect non-absorption or greater O intestinal retention remains to be elucidated.