M. S. D. Shah, S. A. Khan, A. Aslam, M. Rabbani¹, K. A. Khan and M. F. Rai

Department of Pathology, ¹Department of Microbiology, University of Veterinary and Animal Sciences, Lahore, Pakistan.

    In this study, 100 day-old broiler chicks were divided into two groups, A and B containing 50 birds each. Experimental infection with E. coli was given intra yolk to group A on day-1 of experiment, while group B was kept as control. Parameters studied were examination of yolk sac, yolk sac:body weight ratio, antibody titer against Newcastle disease virus (NDV) and analysis of fractional serum proteins. Results showed that yolk sac infection with E. coli led to gross pathological changes of yolk sac (enlarged, discoloured, changed consistency and congested blood vessels). Yolk sac:body weight ratio was increased and geometric mean titer against NDV was decreased in serum and yolk of treatment group. Analysis of fractional serum proteins revealed that percentage area covered by most of serum protein fractions was decreased in treatment group as compared to control group. It was concluded that intra yolk infection with E. coli resulted in pathological changes of yolk sac, increased yolk sac:body weight ratio, decreased immunity and altered serum proteins profile of chicks.   

Key words: Yolk sac infection, Escherichia coli, maternal immunity, broiler chicks.