Seyed Mostafa Peighambari - Department of Avian Diseases, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran

Tiamulin is one of the macrolide antibacterial compounds which is very effective againstmycoplasmas and gram-positive bacteria. This compound is also active against many Gramnegativebacteria other than Enterobacteriaceae family. This drug is used to treat CRD andinfectious synovitis, prevent and control CRD in broiler chickens, prevent and control CRD inbreeder broilers and layers. A total of ۱۰۰۰۰ broiler chicks (ross ۳۰۸) were placed in two houses,each with ۴۰۰۰ birds. Management and nutritional conditions and all health and vaccinationprograms were similar in both houses. Chickens in house ۱ for ۴ days at the age of ۴-۷ days ofage were treated with water-soluble powder Tiamulin ۴۵% (Vetaque Co., Iran) at a daily rateof ۱۰۰ grams in ۴۰۰ liters of drinking water and also at the beginning of week ۴ for ۴ days withthe same drug at a daily rate of ۱۰۰ grams per ۲۰۰ liters of drinking water (DW). Chickens inHouse ۲ were given water-soluble powder Tiamulin ۴۵% (Jamedat Afagh Co, Iran) similar toTiamulin ۴۵% of Vetaque Co. At day ۱, ۲۸ and ۴۲ of age, ۲۰ birds from each house bloodsampled and all the serum samples were tested for MG with RSA test. One percent of chickensfrom each house were weighed at weekly interval until day ۴۹ of age. Food consumption andFeed conversion ratio (FCR) were calculated weekly for each two houses. The percentage ofvarious diseases and complications and mortalities, as well as the autopsy findings, wererecorded in both houses. In each house, ۶۰ chickens were kept as controls without taking anydrugs. The flock did not show any important problem until the beginning of ۴ weeks. Due tothe occurrence of respiratory complications in chickens and the observation of gross pathologyfindings of colibacillosis (fibrinous airsacculitis, perihepatitis, pericarditis) at ۳۰ days of age inboth houses, in addition to Tiamulin ۴۵%, doxycycline ۵۰% with a dose of ۳۰۰ gr/۱۰۰۰ L ofDW were used in both houses for ۴ days. The average weight of chickens in two houses atdifferent ages were compared using SPSS ver. ۱۰ and the Independent-Samples T-test statisticalmethod and no statistically significant difference was observed. The FCR at the end of theexperiment was not significantly different in the two houses. Samples were also taken from thedead carcasses with signs of yolk sac infection or colibacillosis and Escherichia coli wasisolated which showed full sensitivity to florfenicol, Fosbac, doxycycline, and lincospectin andmoderate sensitivity to tiamulin. About ۲۰% of the serum samples taken from day-old chickswere positive for MG with RSA test, but the samples taken at days ۲۸ and ۴۲ of age werenegative for MG. The percentage of mortalities f control birds without medication at the end ofthe period was ۵۵% and their average weight gain in each of the two houses at the end of theperiod was about ۲ kg, which was significantly less than the chickens consuming Tiamulin (P≤ ۰.۰۵). According to the results, no specific difference was found between Tiamulin ۴۵% madetwo companies. At the end of the experiment, the chickens of both houses that receivedTiamulin ۴۵% demonstrated better performance that those of control birds

Broiler, Chicken, CRD-Complex, Colibacillosis, Tiamulin