الفهرس 
Studies on E. coli infections in broiler chickens
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Abstract
The efficacy of protection of prepared inactivated E. coli vaccines were compared with commercially available live attenuated E. coli (Paulvac®) vaccine. Four hundred and fifty one day old broiler cobb chickens were used. Gr (1) were kept as non vaccinated non challenged control negative gr, groups (2-5) were received monovalent prepared inactivated vaccine from E. coli O158 strain , O78 strain ,O114 strain , O125 strain; respectively. While chicken gr (6) received inactivated prepared polyvalent vaccine contains O125,O44,O114,O158,O78 strains, gr (7) received both used polyvalent inactivated vaccine together with live attenuated E. coli vaccine, gr (8) received live attenuated E. coli vaccine only, finally gr (9) received both inactivated prepared O78 E. coli vaccine together with live attenuated E. coli vaccine. Groups (2-5) were challenged intra-crop with homologues viable serogroups O158 strain , O78 strain ,O114 strain, O125 strain; respectively. While grougs (6, 7, 8 and 9) were challenged intra-crop with heterologues viable serogroups O158, O78, O114, O125 and O44. Challenge was done 2 weeks after vaccination, followed by 10 days observation period, performance parameters including body weight/ gm, feed intake and feed conversion rate (FCR) were calculated together with lesion score, clinical signs, mortality rate and histopathological findings were studied