Effect of different levels of Milk thistle (Silybum marianum) seed on performance and some egg quality parameters of laying hens

This experiment was conducted to evaluate the effect of different levels of Silybum marianum seed on performance and some egg characteristics such as egg shell weight, shell thickness, yolk index, yolk color and Haugh unit of laying hens. The experiment was undertaken on hay-line strain (w-36) from 32 to 42 weeks, using a completely randomized design with three treatments, four replicates and four hens in each replicate. The experimental diets were: 1- basal diet (control), 2- basal diet + 1% Silybum marianum seed and 3- basal diet + 2% Silybum marianum seed. The results showed that through performance trait, the average egg weight in treatment having 2% Silybum marianum had a significant increase compared to the control treatment (P<0.05). Although egg production increased in treatments containing Silybum marianum, this increase was not statistically significant. Egg mass in the treatment having 2% Silybum marianum significantly increased compared to the control (P<0.05). Feed intake and feed conversion ratio decreased in the treatments containing Silybum marianum but was not statistically significant. Between egg characteristics, yolk color in the first period was significantly increased by 1% Silybum marianum (P<0.05). Also Haugh unit increased in all treatments containing Silybum marianum, but this increase was significant only in the second period (P<0.05). Based on the results obtained from this research, the use of milk thistle seeds in the diet of laying hens had beneficial effects on performance and egg characteristics such as the Haugh unit in laying hens.