الفهرس 
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Abstract
Three hundred and fifty four chickens (one day old) were used in this work to study the effect of addition of hydroxylamine, vitamins and minerals on the virulence and pathogenicity of NDV infection. The chicken were divided into 4 groups (gps.) 3 experimental and one control,. Each group of the three experimental groups was equally subdivided into 6 subgroups (subgps), included 108 chicks and infected with velogenic, mesogenic or lentogenic NDV respectively. The chickens were fed on the basal diet (subgps 1), supplemented with hydroxylamine (subgp 2), vitamins (subgp 3), minerals (subgp 4), vitamins and minerals (subgp 5) or vitamins, minerals and hydroxylamine (subgp 6), The criteria, used to the evaluation of the efficiency of the vitamins, minerals and hydroxylamine, included mortality rate, clinical signs, antibody titer and the lesions.
The mortality rate in chickens infected with velogenic NDV. 90% (subgp 1 and 2), 80% (subgp 3 and 4) and 65% (subgps 5 and 6). Mesogenic NDV infected chickens showed 50% (subgps 1 and 2), 35%® (subgps 3 and 4), and 20% (subgroups 5 and 6) mortalities. The lentogenic NDV infected chickens showed 5% deaths (subgps 1 and 2) and no mortalities in the remaining subgps.
The chickens infected with velogenic, mesogenic and lentogenic NDV showed general signs (depression, anorexia, yellowish to green diarrhea and ruffled feathers) respiratory manifestations (sneezing, coughing, dyspnea and rals) and nervous signs (termors, convulsions, paralysis in wings and legs, torticollis and opithotonos. The torementioned signs were severe in gp (1) in comparison with gp (2).
The clinical signs were generally mild in chickens of subgp (3. 4, 5 and 6). chickens of gp (3) showed mild clinical signs with absence of the nervous
The lesions in all gps were mostly similar and included congestion of blood vessels, severe desquamation of the lining epithelium and lymphocytic aggregations in the lamina propria of the trachea. The pulmonary lesions were bronchitis, peribronchial lymphocytic aggregations beside hyaline degeneration of the peribronchial smooth muscles., The air sacs were also thickened with fibrinous exudate and lymphocytic infiltrations. Focal coagulative necroses, interstitial lymphocytic aggregations, congested blood vessels and degenerative changes were the main hepatic lesions beside infiltration of the poral areas with round cells. The proventriculus and gizzard showed hemorrhages and ulceration beside hyaline degeneration in the muscles and lymphocytic aggregations in the submucosa and among the muscle fibers„ The intestine showed hemorrhagic ulcers in the mucosa and congested serosal surface. Severe destruction and desquamation of the lining epithelium of the intestinal villi beside lymphocytic aggregations in the lamina propria and hyaline degeneration of the muscle fibers. Cecal tonsils were congested and hemorrhagic. Brain tissue showed congestion of submeningial blood vessels, degenerated neurons, satellitosis, neuronophagia, focal gliosis and focal encephalomalacia beside perivascular lymphocytic cuffing in the brain particularly in birds which were infected with the velogenic strain. Mild neuronal lesions were detected in brains of chickens infected with the mesogenic NDV. The kidneys showed focal coagulative necroses, hemorrhages, interstitial aggregation of lymphocytes and degenerative changes in the renal tissue in chickens which were infected with velogenic and mesogenic NDV.
Meanwhile they were normal in chickens which were infected with the lentogenic NDV„ The lymphoid tissue (spleen and bursa) of chickens which were infected with the velogenic and mesogenic NDV showed necrosis and depletion of lymphocytes in lymphoid follicles. Macrophage and plasma cell- infiltrations in the red pulp beside congsted splenic sinusoids were found. Mild hyperplasia of the lymphocytes in the white pulp of the spleen in chickens infcted with lentogenic NDV was observed, petechial hemorrhages on the coronary fat and among the cardiac muscles beside edema, lymphocytic aggregations among the muscle fibers and hyalinized myocardium were seen. The lesions were generally severe in gp 1 (velogenic) moderate in gp 2 (mesogenic) and mild in gp 3 (lentogenic). Moreover, they were less in severity in subgps 3,4,5 and 6 in comparison with subgps 1 and 2.
Finally, it could be concluded that hydroxylamine showed no effect on the virulence and course of NDV. Meanwhile the supplementation of the vitamins and minerals to the diet of the chickens, before and during the NDV infection, reduced the morbidity and the mortality rates beside the clinical signs and lesions.