The study was conducted in the Department of Animal Production Faculty of Agriculture, Zagazig University, Zagazig, Egypt. The experimental work was carried out at Sakha Experimental Station, Kafer El- Sheikh Governorate, which belongs to animal Production Research Institute, Ministry of Agriculture. The study started at June 2002 lasted for 12 months (June, 2003). The study involved two experiments, were carried out in order to determine the effect of both Moreyeast and Dinaferm on lactating ewes and their lambs (experiment 1) and performance of pre-weaning lamb, performance lamb and carcass quality (experiment 2). The animals were randomly allotted to 6 experimental groups; three groups were fed on 40% concentrate and 60%roughages ratio, while the other three ewe groups were fed on 60% concentrate and 40% roughages ratio. Within each classification the first group was fed on diet without any supplementation (as control group), the second group was fed on the same diet of the first group but supplemented with 5 g Moreyeast/kg ration/ head and the third group was fed on the diet of the first group and supplemented with 1 g Dinaferm /kg ration/ head.Rams which were fed the diet containing 60% concentrate and 40% roughage recorded higher digestibility coefficients (P<0.05) of DM, OM, CP, EE and NFE than the control group. On the other hand, the digestibility coefficients of the nutrients CF the sheep group that fed the diet containing 60% concentrates and 40% roughage was higher than the control group. Rams which were fed the diet supplemented with yeast recorded higher digestibility coefficients (P<0.05) of DM, OM, CP and NFE than the group fed diet without yeast supplementation. Lambs fed diet containing 60% concentrate recorded higher intake values (P<0.05) of TDN% and DCP% than the other experimental group, which was fed 40% concentrate. The nitrogen balance insignificantly affected with the feeding system. Rams group which, was fed diet supplemented with Dinaferm yeast recorded higher values of TDN, DCP and NB than the other experimental groups. Sheep group fed diet containing 60% concentrate and supplemented with Dinaferm yeast recorded higher values of TDN, DCP and NB than the other experimental groups