Effects of dietary thyme and rosemary essential oils on performance parameters with lipid oxidation, water activity, pH, colour and microbial quality of breast and drumstick meats in broiler chickens.

This study was aimed at determining the effects of different doses of thyme essential oil (TEO) and rosemary essential oil (REO) incorporated into broiler rations on performance parameters, including body weight gain, feed intake and feed conversion rate, as well as on the quality criteria of breast and drumstick meat. The study material comprised of 400 three-day-old male Ross 308 chicks, which were assigned to five groups, each of 80 broilers. Each group was divided into four sub-groups of 20 animals. In this study, the feed rations provided to the control group and groups TEO-150, TEO-300, REO-100 and REO-200 were supplemented with 0, 150 mg kg ${}^{-1}$ TEO, 300 mg kg ${}^{-1}$ TEO, 100 mg kg ${}^{-1}$ REO and 200 mg kg ${}^{-1}$ REO, respectively. Fattening performance parameters were statistically similar in the control group and all trial groups ( $P>0.05$ ). It was determined that, while dietary supplementation with TEO and REO significantly reduced total mesophilic aerobic bacteria (TMAB) counts throughout storage in drumstick meat and on days 0 and 8 of storage in breast meat ( $P<0.01$ ), it showed variable effects on other microbial counts and during other time points in both breast meat and drumstick meat. Dietary supplementation with TEO and REO was ascertained not to affect the pH value of breast and drumstick meat and to show limited and variable effects on colour parameters and water activity throughout the storage period of breast and drumstick meat. In all groups supplemented with TEO and REO, the thiobarbituric acid reactive substance (TBARS) levels of drumstick meat were observed to have significantly decreased on days 0, 2 and 4 of storage ( $P<0.01$ ). As a result, dietary supplementation with TEO and REO was determined to have a limited effect on performance parameters, but to improve the microbial quality of meat.