Ferrous fumarate has been demonstrated to be toxic to newborn foals. - GreenMedInfo Summary
Iron toxicity in neonatal foals.
Equine Vet J. 1988 Mar;20(2):119-24. PMID: 3371313
Department of Pathology, College of Veterinary Medicine, Michigan State University, East Lansing 48824.
Newborn Shetland foals died of acute hepatic failure following oral administration of approximately 16 mg/kg body weight ferrous fumarate. Lesions in these foals were indistinguishable from lesions in foals given an oral digestive inoculant containing ferrous fumarate and were also similar to the syndrome characterised as 'toxic hepatopathy' in foals in the United States in 1983. We conclude that foals are susceptible to toxicity from low doses of iron compounds in the first few days of life. Vitamin E and selenium deficiency may contribute to this susceptibility.