The growth rate of Arabi lamb during the suckling period (from birth to weaning at about day 100) is very slow particularly for lambs born in the autumn (Dabiri, 1999). Poor quality and limited quantity of feed for lactating ewes was shown to limit milk production, which was the main reason for slow lamb growth (Dabiri and Mosavi 2000). On the other hand, in conventional Iranian sheep production systems, a limited quantity of low quality supplemental feed (creep feed) is offered to the suckling lambs. I hypothesised that offering a higher quality supplemental creep feed ad-libitum would improve the growth rate of lambs. This would increase the number of weaned lambs for sale at earlier ages for the good market during Eid of Nooroz, the big national celebration in Iran. The growth of lambs may be affected by different sources of protein in the creep feed. Therefore, the aims of this experiment were to 1) compare the growth of lambs fed experimental supplements with the growth of lambs fed conventionally, and 2) compare the effect of diets containing different sources of supplemental protein on lamb growth.