1.1.Young lambs (30–180 h post-partum) responded to low doses of T3 with an increase in V̇O2 within an hour.2.2.rT3 descreased V̇O2 and reversed the V̇O2 stimulation induced by 1 μg/kg T3.3.3.Response to T3 was associated with an increased serum [T3]: subsequent injection with rT3 eliminated this increase.