Abstract
Effects of commercial probiotic (Protexin®), Enterococcus faecium on growth performance, immune response, some blood parameters and carcass traits of broiler chicks were evaluated. A total of 152 Avian-48®, One-day-old chicks were used in this study. The chicks were randomly allotted into 4 equal groups (38 per each) of mixed sex. Protexin was supplemented to the basal diet at 0.0 (control), 0.5, 0.75 and 1.0 g/kg diet (groups 2-4), respectively and the experiment was lasted for 6 weeks, weekly body weight (BW), feed intake (FI) and feed conversion ratio (FCR) were measured. Haemagglutination inhibition (HI) test, Phagocytic activity (PA) and Phagocytic index (PI), differential leucocytic count, some blood parameters and carcass traits were determined. All birds were kept under similar environmental, managerial and hygienic conditions. The results of the current study revealed that addition of Protexin as a probiotic to diets has a slight improvement in total BW, Average daily FI, dressing %, thymus gland weight (wt.) % and bursa wt. % of chicks compared to the control, the highest total body gain was recorded in chicks of group 3 followed by that of group 4 compared with other groups, the best total FCR was noticed in chicks of group3 compared with other groups. No significant difference were observed in HI titer at 21st, 28th, 35rd and 42nd days of broiler chickens in all groups but a significant increase in PA and PI in broiler chicks of group 3 compared with other groups, moreover, the neutrophil count non significantly increased with Protexin addition at 0.5 and 0.75g/kg diet respectively and significantly increased (p < 0.05( in broiler chicks fed the basal diet with at Protexin at 1g/kg diet, the cholesterol ,triglycerides levels and visible fat % were significantly deceased in broiler chicks of all supplemented Protexin groups compared with the control one. The greatest economic efficiency was obtained by group 3 while the lowest and highest levels of protexin (0.5 and 1 g/kg) decreased economic efficiency of production.

Key words: Probiotic, Enterococcus, Growth, Immune, Blood, Broiler.