Abstract. 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.