الفهرس 
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Abstract
The aim of the present work was to study the effect of the source of antibiotics such as zinc bacitracin, virginiamycin, ocytertracycine and erythromycin on the growth performance and feed efficiency, as well as, carcass traits of broiler chichs, the study was also done to study the effect of source pre-probiotics such as lacto - sace and yea-sacc biological products on the same previous parmetrs of broilers.