Do piglets need iron supplementation in organic farms?

Abstract The neonatal pig is prone to iron deficiency, which can lead to growth retardation, cognitive and immune deficits. This study aimed at describing the iron status of piglets at weaning in French indoor and outdoor farms. It was carried out in 11 outdoor and 10 indoor organic farms located in the West of France. In each farm, approximately 30 piglets (half males and females) from 4 to 7 litters were blood sampled. In total, 606 piglets of 42 ± 3 days of age, weighing 12.0 ± 3.0 kg live weight were bled at 1.1 ± 1.7 days from weaning (mean ± SD). Iron injections were used in most indoor farms (400 mg: 1 farm, 200 mg: 8 farms, 100 mg: 1 farm, no supplementation: 1 farm), while in outdoor systems, primarily no supplementation was performed (200 mg: 1 farm, no supplementation: 10 farms). In comparison with the indoor where 200 mg of iron was injected, the outdoor non-supplemented piglets had a greater blood haemoglobin concentration (118 vs 105 ± 3 g/L, P < 0.001) and a higher red blood cell volume (60 vs. 54 ± 1 fl, P < 0.01), indicating a better iron status. In the only indoor farm that did not use iron supplementation, these two variables were low (81 ± 3 g/L and 48 ± 1 fl, respectively), showing an iron deficiency. To conclude, outdoor piglets find a sufficient amount of iron in their natural environment to fulfil their needs, probably by foraging and ingesting soil. Indoors, iron supplementation is necessary, but a single intramuscular iron injection, besides its controversial acceptability in organic farming, might be suboptimal to prevent anaemia in piglets. Thus, there is a need for finding alternative oral solutions to iron injection, ensuring a sufficient, natural and progressive iron intake to newborn piglets