Evaluation of R.I.A. kits for the measurement of thyroid hormones in sheep and cattle sera

ISSN： 1176-0710

Source： New Zealand Veterinary Journal, Vol.33, Iss.7, 1985-07, pp. : 116-117

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Abstract

Hypothyroidism (simple goitre) can be caused by an inadequate intake of iodine or by the presence in the diet of goitrogens which interfere with the utilization of iodine by the thyroid gland. Outbreaks of goitre occur more commonly in the South Island than in the North, usually as a result of wintering pregnant ewes on brassica crops. Reported effects of hypothyroidism in ruminants include placental retention, infertility, lowered milk production, low butterfat content, lowered resistance to infection, increased susceptibility to ketosis, stunted growth and reduced fleece weight and quality. It must be emphasized that in a number of cases these features have been observed under experimental conditions far removed from those likely to be encountered by grazing animals. Early experiments in New Zealand failed to show that mild hypothroidism in older lambs was associated with defective wool growth or reproductive performance in ewes(s) or with poor growth in lambs. One outbreak of goitre and neonatal death was attributed to low stocking rate and a mild winter resulting in reduced soil intake. Other trials have yielded equivocal results. Despite an absence of reliable evidence implicating iodine deficiency as a significant contributor to production losses, there is a growing body of opinion that this situation does exist…