Effects of rosemary essential oils and zinc on performance, egg quality traits, and some serum biochemical metabolites of laying hens

This study was conducted to evaluate the effects of dietary supplement-ation of rosemary essential oils (REO) and zinc (as zinc sulfate) on performance, egg quality traits, and some serum biochemical metabolites of laying hens. A total of 144 44-weeks-old Lohmann LSL-Lite laying hens were randomly allocated into four treatments, each comprising six replicates of six birds. The first group was served as control and fed a corn-soybean meal based diet without REO or zinc supplement. The other three groups received control diet supplemented with 200 mg/kg REO, 40 mg/kg zinc, or both feed additives together. Supplementation of REO and zinc to the diet had no significant (P > 0.05) effects on egg production, egg weight, egg mass, feed intake, feed conversion ratio, body weight and production of abnormal eggs. Compared with the control, egg shape index was increased (P < 0.05) in laying hens fed dietary supplementation of REO. Birds fed dietary REO supplementation had lower (P < 0.05) serum total cholesterol level compared with the control. However, this effect was not observed by combination of zinc and REO. These results indicate that the diet inclusion of REO had a potential to improve the egg quality traits and serum cholesterol level in laying hens.