Abstract
Background:
The combined effects of conjugated linoleic acid (CLA), omega-6 fatty acids, and medicinal plants such as fennel powder and thyme have not been fully investigated in laying hens. Their potential synergistic impact on production traits, blood parameters, and reproductive performance in Lohman LSL laying hens remains unclear.

Aim:
This study investigated the effects of different dietary levels of conjugated linoleic acid (CLA) and omega-6 fatty acids, combined with medicinal plant supplements (fennel and thyme powder), on productive performance and egg quality traits in Lohmann LSL laying hens. Blood lipid profiles, ovarian follicle development, and liver health were also evaluated.

Methods:
Sixty 34-week-old hens (1.5 ± 0.2 kg) were divided into 4 treatments with 5 replicates (3 hens per replicate) over 42 days. Treatments included: control (no additives), T1 (0.025% CLA/omega-6 + 0.025% medicinal plants), T2 (0.0375% CLA/omega-6 + 0.0375% medicinal plants), and T3 (0.05% CLA/omega-6 + 0.05% medicinal plants). Production performance, egg quality, blood lipid parameters, ovarian follicle activity, and liver fat content were assessed.

Results:
Hens fed T2 treatment (0.075% each of CLA/omega-6 and medicinal plants) showed superior production traits (P < 0.05). Egg production percentage significantly differed between treatments and control (89.31% vs 87.07%, P < 0.05). Haugh unit scores improved with higher supplementation levels (82.14 vs 78.66 for T3 vs control, P < 0.05). Blood cholesterol levels decreased in supplemented groups (131.16 mg/dL in T2 vs 148.75 mg/dL in control, P < 0.05). Liver fat percentage was significantly reduced in T2 and T3 groups (34.38% and 33.79% vs 39.43% in control, P < 0.05). Large yellow follicle weight increased in T2 treatment (43.83 g vs 37.79 g in control, P < 0.05).

Conclusion:
Dietary inclusion of 0.075% (0.0375% CLA/omega-6 combined with 0.0375% medicinal plants) optimized production performance, egg quality, blood lipid profiles, and reproductive health in Lohman LSL hens. This supplementation level demonstrated the most pronounced benefits for enhancing poultry productivity and metabolic health.

Key words: CLA; Omega-6; Medicinal plant; Blood parameter; Laying hen.