How to cite this article: performance, behaviour and immunohistopathological response in broiler chicken, 6(6):337-342, doi: 10.5455/ vetworld.2013.337-342 Sureshkumar V, Saratchandra G and Ramesh J (2013) Effect of enrofloxacin on zootechnical Vet. World Introduction immunized with living cells of Salmonella enterica subsp. enterica serovar enteritidis and lipopolysaccharide. In poultry farms, it is a common practice to add Studies conducted in other species revealed that antibiotics in drinking water at the time of vaccination. the presence of circulating antimicrobial residues, Most farmers administer antibiotics at the time of especially fluoroquinolones, in nestlings of the three vaccination without scientific knowledge of the effects vulture species breeding in central Spain resulted in on the immune response. Database on the effects of impaired cellular and humoral immune systems such practices on the immune system is scarce, and compared with nestlings from the control areas, which more authenticated studies are needed to investigate did not ingest antibiotics [4]. the impact of antibiotics on the immune system at the After administration, enrofloxacin is metabolised time of vaccination [1]. in the liver via de-ethylation into pharmacologically Enrofloxacin, a fluoroquinolone developed active metabolite ciprofloxacin [5-7]. Porchezhian [8] exclusively for veterinary use is advocated in poultry in reported that ciprofloxacin significantly reduced the large-scale for treatment of chronic respiratory disease, antibody titre against Lasota and Sheep Red Blood colibacillosis, salmonellosis and fowl cholera [2]. The Cells (SRBC) antigens in broiler chicks. Consequently effect of enrofloxacin on the immune response is not there is every possibility of alteration of immune well documented [1]. However, Tokarzewski [3] response after enrofloxacin administration in broiler revealed that enrofloxacin and chloramphenicol chicken. Further, our earlier study [9] speculated that decreased the level of specific IgY in laying hens the reduction in the lymphocyte count at therapeutic dose of enrofloxacin may have influence on the immune response of the broiler chicken. Hence the present study has been undertaken to www.veterinaryworld.org 337 doi:10.5455/vetworld.2013.337-342 Effect of enrofloxacin on zootechnical performance, behaviour and immunohistopathological response in broiler chicken Veerapandian Sureshkumar, Ghadevaru Sarathchandra and Jayaramachandran Ramesh Pharmacovigilance Laboratory for Animal Feed and Food Safety, Directorate of Centre for Animal Health Studies, Tamil Nadu Veterinary and Animal Sciences University, Madhavaram Milk Colony, Chennai-600 051, Tamil Nadu, India Corresponding author: Ghadevaru Sarath Chandra, email:gsarathchandra@rediffmail.com Received: 17-10-2012, Accepted: 27-10-2012, Published online: 16-03-2013 Abstract 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 rd th 10mg/Kg body weight, through drinking water for five consecutive days from 43 to 47 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 th immunity was observed as evidenced by increased HI titre value noticed from 5 day post treatment onwards and a congruent th reversible trend in histopathological changes as indicated by repopulation with lymphocytes on 9 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. Keywords: broiler chicken, enrofloxacin, immunohistopathology, safety pharmacology, zootechnical performance This article is an open access article licensed under the terms of the Creative Commons Attribution License (http://creativecommons. org/licenses/by/2.0) which permits unrestricted use, distribution and reproduction in any medium, provided the work is properly cited.