Objectives: Yolk sac infection is one of t he most important diseases in poultry that causes severe mortality rates in broilers at the first week of breeding. Different kinds of bacteria are involved in yolk sac infection. Coliforms, specially Escherichia coli are one of the main casual agents of the disease. Applying through management and principles of egg hygiene, from the period of egg laying until putting the egg in the setter, minimizes the rate of bacterial penetration through egg shell and decreases the risk of disease’s incidence. Materials & Methods: Since pathogenic agents mainly cause infection through penetrating egg shell, hygiene and management methods in parent stocks and hatcheries play a basic role in prevention of the disease. In this study 120 hatchable eggs from different stages (immediately after laying (1), before disinfecting (2), after disinfecting (3), before putting in the setter (4) and 30 day-old chickens(5) were collected from parent stocks. After referring to the microbiological lab, samples were tested for the coliform infection rate, in egg shell, egg yolk and yolk sac. Results & Conclusion: In the first stage 11 of 30 egg shell samples were positive for coliform infection, of which Escherichia coli was isolated from 7 samples , Enterobacter from 5 samples and Citrobacter from 4 samples . In the second stage 6 egg shell samples were positive for coliform infection, of which, Escherichia coli was isolated from 4 samples , Enterobacter from 4 samples and Citrobacter from 1 sample. In these two stages no coliforms were observed in the yolk cultures. In the third stage no coliforms were observed in the shell and yolk cultures. In the forth stage no coliform were observed in the shell and yolk cultures. In the fifth stage no coliforms were observed in the yolk sac cultures. According to the obtained results, coliform infection commonly exists on the egg shell. In the absence of suitable disinfecting, infection gradually penetrates through the egg shell and infects yolk sac of one-day old chickens through egg yolk. The aim of this study was determining the frequency and types of coliforms in egg shell and egg yolk in different stages, in order to provide a suitable guide for future studies to improve the management and disinfecting methods of the egg. Keywords: Coliform, Escherichia coli, Citrobacter, Enterobacter, Yolk Sac Impact of vitamin E depletion on nutritional Encephalomalicia in chicks Maha M, Hady A Professor and Head, Department of Nutrition and Clinical Nutrition, Faculty of Veterinary Medicine, Cairo University, Egypt Corresponding author\'s

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