The effect of propolis addition to the laying-hen diet on performance, serum lipid profile and liver fat rate.

The aim of this study was to evaluate the effect of propolis (P) on performance, egg quality parameters, serum lipid profile, some liver enzymes and liver fat ratio. One-hundred-and-twenty Lohmann (LSL) laying hens were divided into five groups, and each group consisted of six subgroups. The control group was fed basal diet. The other groups were fed high-energy (HE) diets to induce fatty liver syndrome, and 0, 100, 200 and 300 mg kg${}^{-1}$ of propolis were supplemented with high-energy feeds. During the 8-week trial, feed and water were given ad libitum. It was determined that egg production and feed conversion ratio were decreased in the high-energy feed group without the addition of propolis. The highest egg production was found in HE $+$ 100 and HE $+$ 200 mg kg${}^{-1}$ of P groups. It was found that liver fat ratios were higher in the group fed with HE $+$ 0 mg kg${}^{-1}$ of P feed ($P<0.01$) than other groups. But the addition of P decreased the liver fat rate significantly. The highest very low density lipoprotein (VLDL), triglyceride (TG) and low-density lipoprotein (LDL) values were found for the HE $+$ 0 mg kg${}^{-1}$ of P group. The addition of 200 mg kg${}^{-1}$ of P to high-energy feed increased glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) values. In conclusion, high-energy feed adversely affected egg production and liver fat ratio, but the addition of 100 or 200 mg kg${}^{-1}$ of propolis improved egg production and decreased liver fat ratio.