Ingested soil and iodine deficiency in lambs

Abstract

Abstract Post‐mortem and clinical examination of lambs on the Department of Agriculture Field Research Area at Masterton in 1971 showed that there was a high prevalence of enlarged thyroids in lambs from ewes on low‐stocked areas; the condition was almost entirely absent in lambs on high‐stocked areas. Faeces from ewes on high‐stocked areas which were closely grazed contained substantially more soil than did faeces from ewes on lowstocked areas which had ample feed in winter 1971. Iodine in faeces followed a similar pattern to soil in faeces. Iodine in herbage showed no differences between high‐ and low‐stocked areas. The data suggest that ingested soil was a source of iodine to ewes on high‐stocked areas and that this accounts for the virtual absence of enlarged thyroids in the lambs. Possible reasons for the appearance of goitre in 1971 are considered.