الفهرس 
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Abstract
Avian colibacillosis has been found to be a major infectious disease of all ages of birds. It primarily affects broiler chickens between the ages of 4 and 6 weeks and is responsible for a significant proportion of the mortality found in poultry flocks. This mortality, treatment of the disease and decreased feed conversion efficiency result in significant costs to the poultry industry.
Norfloxacin is a broad-spectrum antibiotic that is active against both Gram-positive and Gram-negative bacteria, occasionally used to treat clinical common as well as complicated urinary tract infections.
Antibiotics are used by the poultry industry and poultry veterinarians to enhance growth and feed efficiency and reduce disease. Antibiotic usage has also enhanced the health and well-being of poultry by reducing the incidence of disease. Although these uses benefit all involved, unfortunately, consumer perceptions are that edible poultry tissues are contaminated with harmful concentrations of drug residues. In a recent consumer survey, reported that 77% of consumers responding considered animal drug residues in meats to be an extreme health concern.
So that it was necessary for us to search for new alternatives which used for prevention and treatment of the diseases. These are natural substances which can be used for stabilizing and improving intestinal microflora.