Changes in body content of iron, copper and zinc in Iberian suckling piglets under different nutritional managements

Thirty-eight purebred Iberian sows were used in two consecutive trials to determine the influence of different nutritional strategies applied to the litters on body composition and retention of some trace minerals in the body of suckling piglets weaned at 35 d of age. Exclusively milk feeding (M), conventional suckling (CS) and intermittent suckling (IS) were studied. Only litters on CS and IS treatments had free access to creep feed from day 15 onwards. Those of the CS group had continuous access to their dams. Piglets on the IS treatment were progressively separated from the sow during 6 h, 8 h and 10 h on days 29-30, 31-32 and 33-34, respectively. Eight piglets at birth (4 per trial replicate) and one piglet per litter on day 35 of age were slaughtered and used to study whole-body content of Fe, Cu and Zn, and its distribution in the different body compartments. Mineral retention was calculated following the comparative slaughter procedure. Average contents of these trace elements in Iberian sows' milk were Fe 1.65, Cu 1.46 and Zn 11.10 mg/kg, whereas those analyzed in creep feed were Fe 240, Cu 170 and Zn 2900 mg/kg (as fed). The body concentration of Fe at weaning was unchanged between groups, although Fe stored in liver tended to be higher in IS piglets (32.3, 30.5 and 50.0 mg/kg for M, CS and IS piglets respectively, P=0.101). No differences (P>0.05) were observed in whole-body or liver concentration of Cu between groups, although Cu concentration was increased (P<0.01) in some body compartments (blood and head/feet/tail) in CS and IS compared to M piglets. Significant effect of the feeding regimen was found in body levels of Zn in weaned piglets, as retention and body content resulted progressively increased as follows: IS > CS > M groups (P<0.001), with significant differences for all body parts. Zn liver concentration increased around 3-fold in creep fed piglets compared to milk fed piglets (53, 149 and 157 mg/kg for M, CS and IS piglets, respectively, P=0.029). It may be concluded that stimulation of consumption of solid feed containing pharmacological levels of these trace elements in the suckling piglet may lead to some changes in body content of Fe and Cu at weaning, and increases greatly Zn body levels. Beneficial consequences of these nutritional practices warrant to be evaluated, as they cause substantial increase in environmental contamination.