Copper and molybdenum in swayback pastures

Swayback disease of lambs occurs widely in Britain, its incidence varying from year to year, but is usually most severe in lambs born in March and April after a mild winter. It is known to be related to a copper deficiency in both the ewe and the lamb, but not all copper-deficient owes give birth to swayback lambs. The disease can be effectively prevented by administering copper compounds to ewes in susceptible flocks at mid-pregnancy (Allcroft, Clegg & Uvarov, 1959).