Abstract
Abstract
Tylvalosin tartrate is a macrolide antibiotic that has antibacterial activity against Gram-positive, some Gram-negative organisms, and mycoplasma. It acts by inhibiting protein synthesis in bacterial cells. Mycoplasma gallisepticum causes chronic respiratory disease in poultry, especially in the presence of management stresses and other respiratory pathogens. The disease is characterized by coryza, conjunctivitis, sneezing, and sinusitis, particularly in turkeys and birds. It can result in loss of production downgrading of meat-type birds, and loss of egg production. In the current study, the efficacy of tylvalosin on performance parameters, hematological and biochemical profile alone, and in combination with eucalyptus oil and bromhexine were studied. A total of 56-day adult chickens were used in the experiment and infection occurred by Mycoplasma gallisepticum. The birds were classified into seven groups and treated as follows; non-infected non-treated group (control negative), infected non-treated group (control positive), group infected and treated by tylvalosin alone, group infected and treated by eucalyptus oil, group infected and treated by bromhexine, group infected and treated by tylvalosin plus eucalyptus oil, and group infected and treated by tylvalosin plus bromhexine. Clinical symptoms, bacterial re-isolation, mortality rate, and hematobiochemical and histopathological parameters were investigated. The results showed a significant decrease in mortality & improved growth performance (increased weight gain and feed utilization efficiency) in combined treated groups compared to tylvalosin group as well as improvement in hematobiochemical and histopathological parameters of combined treated groups. Furthermore, the combination of tylvalosin and eucalyptus oil or bromhexine was more potent in the treatment of Mycoplasmosis in chickens than each treatment alone and alleviated or partially reduced the severity of chronic respiratory disease induced by Mycoplasma gallisepticum in broiler chickens. Finally, this protective effect could improve the use of antibiotics in poultry farms as well as reduce the problem of antibiotic residues and bacterial resistance to antibiotics.

Key words: : Bromhexine; Chickens; Tylvalosin; Mycoplasma gallisepticum; Eucalyptus oil.