The placenta prevents the transfer of maternal immunity to the foetus and consequently lambs are born hypoimmunocompetent. The IgG content in colostrum and its absorption into the blood stream has important consequences for lamb liveability in early life. Recent experiments carried out at this institute found that when ewes had access to a mineral block or the mineral component of this block in the form of powdered minerals in late pregnancy, the absorption of IgG by their offspring was reduced (Boland et al., 2003). Keane (2001) stated that it would appear that the lamb was pre-programmed in-utero for lowered IgG efficiency and that the problem lay with the lamb rather than to any altered characteristics of the colostrum. The aim of this experiment was to investigate the period of time necessary for high levels of mineral supplementation to the ewe to affect a reduction in IgG values in the progeny.