Problem statement:In trying to finding phytogenic antibiotic-substitutes this study was done and effects of adding graded levels of Medicinal Herbs (MH) including garlic (Allium sativum) and thyme (Thymus vulgaris) to laying hens' diet on productive performance investigated. Approach: A total number of 108 Lohmann LSL-Lite hens after production peak were randomly divided in 18 cages (n = 6). Three iso-energetic and iso-nitrogenous experimental diets (ME = 2720 Kcal Kg ) including three levels (0, 1 and 2 g kg) of ground mixture of garlic and thyme (1:1) were fed to hens with 6 replicates per diet during 6 week trial period. Collected data of Feed Intake (FI), Egg Production (EP), Egg Mass (EM) and calculated Feed Conversion Ratio (FCR) as well as egg traits were analyzed based on completely randomized design using GLM procedure of SAS. Results: Dietary treatment did not have significant effect on EP, EM and FCR in laying hens (p>0.05). Dietary inclusion of MH decreased FI in weeks 1-6 (p≤0.05). Including diet with 0.1% MP improved means of egg weight (g) comparing to the other two experimental diets. Adding 0.2% MH to diet increased egg yolk color as well as blood lymphocyte counts and decreased egg shell weight comparing to other dietary treatments (p≤0.05). Conclusion: In conclusion, dietary inclusion of garlic and thyme can have beneficial effects on performance of laying hens in terms of improving egg weight and yolk color.

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