Effect of dietary levels of milk thistle extract (Silybum marianum) on serum parameters and egg quality in laying hens imposed to dexamethasone-induced stress

The aim of the current study was to determine the effects of different levels of milk thistle extract on productive performance, blood parameters and egg quality in laying hens imposed to dexamethasone-induced stress. The 2×3 factorial experiment was managed in a completely randomized design with 72 Hy- Line (W36) laying hens in 6 treatments and 4 replicates of 3 birds each. The experiment was carried out from the age of 75 to 81 weeks. Hens were weighed and either remained uninjected or received injections dexamethasone (0 and 4 mg per bird). The milk thistle extract were included at 0, 100 and 200 mg/kg in diets. The dexamethasone injections caused reductions in egg production percentage and egg mass in the throughout the experimental period (P<0.05). Laying hens imposed to dexamethasone-induced stress had the highest feed conversion ratio (P<0.05). The highest amount of lymphocytes in blood were observed in groups supplemented with 200 mg/kg of milk thistle extract (P<0.05). HDL content in serum was increased by the inclusion of milk thistle extract (200 mg/kg) (P<0.05). Adding of milk thistle extract to the diet of laying hens caused a significant decrease in LDL content in serum (P<0.05). In general, stress induced by dexamethasone injection reduced egg production and increased feed conversion ratio and addition of milk thistle extract to the diet had no positive impact on performance in laying hens.