Do piglets need iron supplementation in organic farms?

Summary

This study aimed at describing the iron status of piglets at weaning in French indoor and outdoor farms. It was carried out in the spring of 2019 in 20 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, 565 piglets of 42.1±3.2 days of age, weighing 12.0±3.0 kg live weight were bled at 1.1±1.7 days from weaning (mean±SD). Among the 11 outdoor and 9 indoor organic farms that were investigated, iron injection was used in most of indoor farms (200 mg: 8 farms, 100 mg: 1 farm, no supplementation: 1 farm), while in outdoor systems, mostly no supplementation was performed (200 mg: 1 farm, no supplementation: 10 farms). In comparison with the indoor/iron injected piglets, the outdoor/non-supplemented piglets had a greater blood haemoglobin concentration (118 vs. 105 ± 2 g/L, mean±SE, P < 0.001) and a bigger red blood cell volume (60 vs. 56 ± 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), suggesting an iron deficiency. To conclude, outdoor piglets find a sufficient amount of iron in their natural environment, probably by foraging and ingesting soil, to fulfil their needs. Indoors, an 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 solutions to iron injection for newborn piglets.