Abstract:
This study was carried out in Khartoum North area to isolate and identify the bacteria associated with respiratory tract infection in chickens and to determine the effects of common identified bacteria on broiler performance ( growth rate , feed intake , feed conversion ratio ,weight gain ,carcass quality and mortality ) and hematological .
Seven hundred and twenty Samples were collected from Poultry Market (Bahary and KuKu Market) , East of Nile farms , central of Khartounm North farms (Shambat and Samrab). Samples were a aseptically collected from different breed of chickens (Balady , Fioumy and Hybreed) showing clear respiratory signs .
Sterile cotton swabs were used for taking samples from trachea, lung , spleen, Liver, intestine and reproductive system . The collected samples showed bacterial growth and yielded 325 isolates (45.14%) Gram-negative bacteria , 253 isolates(35.17%) Gram - positive and the remaining 142 (19.72% )were showed no growth .
Gram –negative bacteria isolated were : Escherichia coli , Citrobacter freundii, Haemophilus paragallinarium , Pseudomonas diminuta and Pseudomonas aeruginosa . Broiler chickens were experimentally infected by the most common isolated bacteria (Escherichia coli and Citrobacter freundii) . The infected birds showed significant decrease in feed intake and weight gain while feed conversion ratio and mortality rate were increased .
The highest mortality (19.05 %) was recorded in group (B)which was infected by Escherichia coli .
Carcass and non carcass characteristics were not affected by experimental infection of broiler by either with Escherichia coli nor with Citrobacter freundii but, there was slightly increase in weight of the head and heart . Experimental infection of broiler chicks with either Escherichia coli or Citrobacter freundii significantly affected blood parameters ; White blood cells count were increased two days after infection , Red blood cell count , packed cell volume and haemoglobin concentration were decreased .
Broiler chicks infected with Escherichia coli showed loss of appetite, decreased, feed intake, mucous nasal discharge and diarrhea.
