ABSTRACT
Difloxacin is a recent fluoroquinolone antibacterial .The aim of this study to evaluate the effect of difloxacin on the immunity of chickens before and after vaccination with Newcastle disease .Sixty hubberd one day old chicks were divided into 2 equal groups. for 2 experiment the first one contain 2 groups group A was control, group was treated with difloxacine [1 ml/litre of drinking water] for 5 successive days before vaccination two groups vaccinated with lasota at 20 days of age and 2[nd] experiment contain group c vaccinated with lasota at 20 days of age group D was treated with difloxacine [1 ml/litre of drinking water] for 5 successive days after vaccination. The result showed that there was significant decrease in WBCs, lymphocytes and phagocytic assay in the 1st week in group treated before vaccination but in 1st and 2nd week in group treated after vaccination. On the other hand there was significant increase in AST level in group treated before vaccination in addition to this results there was significant increase in uric acid in group treated after vaccination only. Also there were non significant changes in total protein, albumin and globulin. Also there were significant decrease in the weight of thymus and bursa in 1st and 2nd week respectively in group treated with difloxacin before vaccination, but there was significant decrease in the weight of thymus and bursa only in 2nd week in group treated with difloxacin after vaccination. Beside these result there results there was slight decrease in heamagglutination inhibition [HI] to Newcastle disease specially in group treated with difloxacin after vaccination