A total of 88 ewes were used in this study in two trails (44 per each trail) to investigate the effects of supplementation of probiotic abbreviated as (Effective Microorganisms with Medicinal Herbs-EMMH) on physiological responses during thermonuteral and heat stress conditions and milk yield of two local breeds (Farafra and Saidi). The studied probiotic consisted of mixed culture of two strains of fungi (Trichoderma reesei and Aspergillus oryzae) with dry live baker's yeast (Saccharomyces cervisiae) and the mixed culture was enriched with natural antioxidants of herbal medicine plants. In the first trail, 22 Farafra and 22 Saidi ewes were used during summer, along mating and pregnancy seasons until parturition. In the second trail, 22 Farafra and 22 Saidi ewes in late pregnancy were used. Ewes of every breed were divided homogonously into two equal groups (11 ewes per each). Group (I) fed basal diet (concentrate feed mixture + rice straw). Group (II) fed basal diet + 3 kg EMMH/ton. Reproductive traits were estrus duration, conception rate (%) and gestational period, number of lambs born, number of twins and birth weight was recorded. Thermal responses, gas exchange parameters and heat production measurement were determined during thermoneutral (comfort) conditions and during heat stress condition (after exposing animals to direct sun for 2 hours). Also, climatological data were recorded periodically. Daily and total milk yield were measured along the lactation season using lambs sucking technique. Body weight gain of suckling lambs, weaning weight and survival rate were recorded. Also, values of heamatocrit % (Ht), total protein (TP) sodium (Na), Potassium (K) and total antioxidant capacity (TAC) were determined in ewes. In thermonuteral conditions, EMMH supplemented group had significantly (P< 0.05) lower rectal temperature than control group in Farafra ewes. Whereas, in heat stress conditions, rectal and skin temperature significantly (P< 0.05) decreased in EMMH supplemented group in both breeds. Respiration rate was significantly (P< 0.05) lower in supplemented group than control in Farafra ewes only. Tidal volume was significantly (P< 0.05) higher in EMMH group. While, metabolic rate and heat production values were significantly (P< 0.05) decreased in EMMH supplemented group. Average body weight and body weight change of ewes significantly (P <0.05) improved by EMMH supplementation. Conception rate was improved in EMMH group compared to control in both breeds (90.9% vs. 72.7% in Farafra ewes) and (81.8 vs. 72.7% in Saidi ewes). Furthermore, average litter size per ewe, number of lambs born per group, number of twins born per group were improved by EMMH supplementation. Total milk yield, average daily milk yield per ewe, weaning weight and total gain of lambs were significantly (P<0.05) improved by EMMH supplementation in both breeds. Also, survival rate was improved in EMMH group in both breeds. Values of total protein concentration (TP) and total antioxidant capacity (TAC) was significantly (P <0.05) higher in EMMH supplemented group in both Farafra and Saidi. From the present results, it can be concluded that supplementation of EMMH probiotic had a favorable effect in improving physiological responses of animals during heat stress and can ameliorate the adverse effects of heat stress. Also, it led to improve lactational performance of ewes and the performance of their suckling lambs.