Ovine congenital goitre associated with minimal thyroid enlargement

Abstract

An outbreak of congenital goitre associated with minimal thyroid enlargement resulted in a high level of lamb mortality (36.1 per cent) in a flock in northern Tasmania. Palpation was shown to be a valid means of assessing thyroid gland size and a significant linear relationship between thyroid size and lamb mortality was demonstrated (P < 0.01). Although the overall difference in mortality rate between normal and goitrous lambs was significant this was confined to the middle of the birth weight range; at either end of the range the normal and goitrous lambs experienced similar levels of mortality. Goitrous lambs died earlier and had less chance of walking or metabolising their fat reserves than their normal counterparts. There was no effect of sex or type of birth (single or multiple) on incidence of goitre. In most of the goitrous lambs that survived, thyroid size had regressed to normal in about six weeks.