Intestinal fate of dietary zinc and copper: Postprandial net fluxes of these trace elements in portal vein of pigs

In pig, the assessment of bioavailability of dietary trace minerals with classical approaches such as relative bioavailability estimates or digestive tract balances have often generated inconsistent responses. In the present study, net portal-drained-viscera fluxes were monitored after a meal to assess intestinal absorption of zinc (Zn) or copper (Cu) according to dietary sources and levels of these trace minerals. Twelve pigs were surgically equipped with portal and carotid catheters and a portal ultrasonic flow probe for 12-h postprandial measurements. In a cross-over design, pigs received boluses of inorganic (I) or organic (O) dietary Cu and Zn at adequate (A, 20 and 200 mg, respectively) or high (H, 40 and 400 mg, respectively) level just before a 0.8-kg meal (semi-purified diet). Whatever treatments, arterial Zn increased by 72% at 45 min postprandial and gradually declined thereafter (P < 0.01). Arterial Zn were greater by 11% after O than I (P = 0.02) and by 19% after H than A (P < 0.01) meals. Net portal-drained-viscera fluxes of Zn during the first 240 min postprandial were greater by 44% after O than I (P = 0.10) and by 51% after H than A (P = 0.07) meals. For Cu, portal-drained-viscera fluxes of Cu up to 240 min postprandial were greater (P = 0.03) after A than H meals. Those results suggest that Zn is absorbed rapidly, likely in the upper digestive tract of pigs and, whatever dietary levels, more efficiently after O meals. It appears that H levels of both Zn and Cu interfered with intestinal absorption of Cu and/or stimulate post-absorption enterocyte sequestration of this mineral.