Lambs are born hypoimmunocompetent as the placenta prevents the transfer of maternal immunity to the foetus of the ruminant. Colostrum is the source of imunoglobulins for the young lamb and any interference with the absorption of immunoglobulins from colostrum would have important consequences for lamb liveability in early life. Recent experiments at this institute found that when ewes had access to mineral blocks in late pregnancy the absorption of immunoglobulin (IgG) by their offspring was reduced (Keane 2001). This author also stated that the lamb was preprogrammed in-utero for lowered IgG absorption efficiency. The aim of this experiment was to determine whether it was the mineral or molasses component of the mineral block which caused the reduced IgG absorption by the lamb.