Colibacillosis is one of most important infectious diseases of poultry caused by Escherichia coli. Enrofloxacin, an antibiotic, is commonly used against colibacillosis in poultry. In this study, we compared the efficacy of two commercial product of enrofloxacin ۱۰% in a broiler flock. Two houses (۱ and ۲) were selected in a broiler farm in Qazvin province, each with a capacity of ۱۰,۰۰۰ chicks of the Cobb breed. Management and nutritional conditions and all health and vaccination programs were the same in both houses. By observing the respiratory complications, signs and deaths due to colibacillosis from the beginning of the fourth week in the houses and after performing the antibiogram test, the chickens in the house ۱ from the age of ۲۸ days onwards received POLISTAR (enrofloxacin ۱۰%) oral solution (POLICHEM Laboratories. Spain) in drinking water for ۵ days. The chickens in house ۲, as control group, also received enrofloxacin ۱۰% (Hipra, Spain) in drinking water for ۵ days from the age of ۲۸ days. Before administering the drug, sampling and bacteriological culture were done from the dead carcasses with colibacillosis lesions. After the isolation of Escherichia coli
bacteria, antimicrobial sensitivity test was done. Seventy chicks from each house from ۲۱-۴۹ days old were weighed at weekly interval. Food consumption and the final conversion coefficient were calculated at the end of the course in both houses. The percentage of various diseases and complications and the resulting deaths were recorded also in both houses. The results obtained regarding each of the aforementioned parameters in two houses were compared and analyzed with appropriate statistical methods. Administration of two antibiotics reduced mortalities and improved respiratory symptoms in both houses. At the end of the production period (۴۹ days), the number of mortalities in house ۱ was equal to ۶۳۸ chicks (۶.۳۸%), which was slightly less than ۶۴۵ pieces (۶.۴۵%) of mortalities in house ۲. The production parameters were not significantly different at the end of the production period in two houses. Our findings showed that two commercial enrofloxacin ۱۰% evaluated in this study did not have any particular difference, and therefore, both can be used against colibacillosis in poultry.