Abstract

    The present project was carried out to study the effect of experimental yolk sac infection with Staphylocvccus aureus on immune status of broiler chicks. For this purpose, one hundred day-old chicks were divided into two groups A and B. having fifty chicks each. Confirmed pathogenic isolate of Staphylocvccus aureus was inoculated into the yolk of each chick of group A. while group B acted as control group. Parameters studied included pathological examination of yolk sac, yolk sac weight/body) weight ratio, antibody titres against Newcastle disease virus (NDV) in serum and yolk and analysis of fractional serum proteins, Results showed that yolk sac weight/body weight ratio was higher with marked pathological changes (abnormal colour, consistancy and odour) were also observed in unabsorbed yolks of the infected group. Geometric mean titres of maternal antibodies against NDV were significantly lower in serum but higher in unabsorbed yolks of infected group than in control one. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was used for serum protein analysis and percent area covered by each protein fraction was calculated. The percent area covered by most serum protein fractions was lower in infected chicks than the control chicks. It was therefore concluded that yolk sac infection (omphalitis) with Staphylocvccus aureus led to decline in the immunity.