Effects of natural oral alternatives to parental iron supplementation on haematological and health-related blood parameters of organic piglets

•Alternatives to injectable iron are needed for indoor organic pig farming.•Indoors, daily provision of peat-like river silt effectively prevented anaemia in piglets.•Indoors, daily supply of soil failed to prevent anaemia in more than 5% of piglets.•Indoors, 100-mg injectable iron failed to prevent anaemia in more than 5% of piglets. The most common and efficient iron supply to prevent neonatal anaemia in piglets is the injection of iron dextran or gleptoferron. This treatment is problematic in organic farms because organic specifications strictly limit the use of chemically synthesised allopathic drugs. Based on the observation that piglets raised outdoors rarely develop anaemia, we hypothesised that piglets satisfy their iron needs by ingesting soil from their environment. Therefore, we compared the efficacy of a 100-mg intramuscular iron dextran injection (Iron, 8 litters, n = 98 piglets) at 4 days (d) of age (d4), to a daily ad libitum supply of dried soil (Soil, 8 litters, n = 101) or dried peat-like river silt (Peat, 8 litters, n = 102) from d4 to weaning (at 49 days of age, d49). Pigs were raised according to organic farming rules. Blood was collected on three males and three females per litter on d4, 20, 41, 50 and 69. BW was similar in the three groups on d4, 20, 41, 50 and 69 (P > 0.1). During the experiment, piglets were affected by a severe digestive E. coli episode but litter mortality rate between d4 and d69 did not differ between groups (P > 0.1). Blood haemoglobin concentration (Hb) was similar in all groups on d4, 50 and 69. However, on d20, Hb was higher in Peat and Iron groups than in the Soil group (P