Effect of enrofloxacin on zootechnical performance, behaviour and immunohistopathological response in broiler chicken

Aim: A safety pharmacology trial was conducted to evaluate the impact of enrofloxacin on zootechnical performance, behaviour and immunohistopathological response in Newcastle disease virus vaccinated broiler chicken after pulsed water medication. Materials and Methods: Experimental group birds were administered with enrofloxacin at recommended therapeutic dose 10mg/Kg body weight, through drinking water for five consecutive days from 43rd to 47th day of age. Zootechnical performance parameters, behavioural and humoral immune response in terms of haemagglutination inhibition (HI) titre were assessed at different time interval during pre-treatment, treatment, post-treatment period. Bursa of Fabricius and spleen tissues collected at each sampling point viz. 1, 3, 5, 7 and 9 days post treatment were subjected to histopathological examination. Results: A significant reduction in HI titre was noticed in enrofloxacin administered birds. The decreased HI titre was further substantiated by the histopathological changes observed in bursa of Fabricius and spleen which showed a lymphocytic dispersion and depletion with several areas of lymphoblastic degeneration. Conversely, a down regulatory effect on humoral immunity was observed as evidenced by increased HI titre value noticed from 5th day post treatment onwards and a congruent reversible trend in histopathological changes as indicated by repopulation with lymphocytes on 9th day post treatment. However, there was no significant change in body weight, cumulative feed intake, feed efficiency and behaviour in enrofloxacin administered groups. Conclusion: The present study suggests that the immuno suppressive activity of enrofloxacin may alter the immune response to vaccines, if it is coadministered during vaccination of broilers. On the other hand, enrofloxacin, though it decreased the humoral immune response, it did not have any appreciable effect on broiler's performance.