Seema R. Nimbarte
Poultry is widely recognised as an important source of protein, vitamins, minerals, and fats. However, poultry production is frequently affected by infections in birds, which adversely affect the prospects of the industry. Consequently, poultry farmers have made extensive use of antibiotics to control infections. This practice has contributed to the development of antibiotic resistance among common pathogens encountered in the poultry industry. The present study was therefore conducted to evaluate the potential of the essential oils of Thymus vulgaris and Melaleuca alternifolia (thyme oil and tea tree oil, respectively) as antimicrobial agents against broiler pathogens and for possible use in poultry feed. Both oils were assessed for antibacterial activity against pathogens isolated from infected chickens, namely Escherichia coli, Staphylococcus aureus, Staphylococcus carnosus, and Salmonella gallinarum. Antimicrobial activity was assessed using the disc diffusion method, and the minimum inhibitory concentrations (MICs) of the oils were determined using a 96-well microbroth dilution method. The diameters of the zones of inhibition ranged from 19 to 34 mm. MIC values ranged from 0.07% to 0.15% for tea tree oil and from 0.019% to 0.039% for thyme oil. A feeding trial was subsequently conducted using standard procedures, in which Indian broiler chickens received feed augmented or fortified with essential oils for six weeks. The experimental birds had a lower recorded prevalence of infection. The birds also gained substantial body weight during the trial, indicating that essential-oil supplementation did not adversely affect their health.