To determine the effects of adding essential oils of rosemary, dill and chicory extract to diets on performance, egg quality and enzyme activity of laying hens subjected to heat stress, a total of 240 laying hens were used and based on a 2 × 2 × 2 factorial, eight diets, with five replicates, including basal diet with two levels of rosemary essential oil (0, 20 ml/100 kg), two levels of dill essential oil (0, 15 ml/100 kg) and two levels of chicory extract (0, 250 ml/100 kg) were fed to the experimental birds. Dietary dill had a significant effect on egg index under heat stress condition. The birds given rosemary, dill and chicory alone exhibited lower serum cholesterol and triglycerides concentration under thermoneutral and heat stress condition compared to those fed the basal diet (P < 0.05). Synergistic effects between dietary rosemary, dill and chicory significantly increased plasma glutathione peroxidase activity compared to those that received only rosemary, dill or chicory, which has been never reported (P < 0.05). In conclusion, the addition of single or combination of rosemary, dill and chicory can improve at least some production performance and antioxidant enzyme activity (glutathione peroxidase) in heat-stressed laying hens.

Background: Organic products of animals are getting more accepted by consumers. Using herbal additives may lead to more health animal products. In this research it is hypothesized thatLavandula angustifoliaand/orMentha spicataessential oils would be helpful to enhance production performance in laying hens.Objectives: This experiment was conducted to evaluate the effects ofLavandula angustifoliaandMentha spicataessential oils on performance, egg traits and blood variables in laying hens.Methods: 144 Lohmann LSL‐Lite laying hens from 42 until 56 weeks of age were used in a completely randomized design in four treatments and six replicates (six birds per replicate). The treatments consisted of: (a) control group (basal diet), (b) basal diet supplemented with 250 mg/kg diet lavender essential oil (LEO), (c) basal diet supplemented with 250 mg/kg diet mint essential oil (MEO), and (d) basal diet supplemented with both LEO and MEO.Results: Using LEO and/or MEO did not affect body weight changes, feed intake, egg weight, egg index, yolk index, Haugh unit, egg shell weight and egg shell thickness. Feeding LEO, individually or in combination with MEO, did not affect FCR compared with the control group (p < .05), however, feeding MEO individually increased feed conversation ratio (FCR) compared to LEO and the control group during 42–56 weeks (p < .05), as well as decreasing egg mass compared to LEO (p < .05). Feeding LEO increased egg production compared to MEO and combination of MEO and LEO (p < .05).Conclusions: In conclusion, dietary supplemental MEO (250 mg/kg) may increase FCR, and LEO (250 mg/kg) is more effective than MEO (250 mg/kg) for egg production and egg mass purposes; besides MEO (250 mg/kg) negatively affected FCR compared with the control group. In addition, no specific beneficial effect of dietary supplemental MEO and/or LEO on the other measured variables was detected.