A 3 × 2 factorial arrangements with completely randomized design, with a total of 72 Leghorn Hy-line (W-36) laying hens in the second cycle (98 wk old) of production were randomly assigned to 24 wire cages (45.7×30×30 cm3) and fed with diets containing three levels of guar meal (GM; 0, 4 and 8%) and two levels of β-mannanase (Hemicell®) enzyme (0.00 and 0.05%) for 12 wk period. There were four replicates per treatment with three hens in each replicate. Egg yolk cholesterol and serum lipids (triglyceride, cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C)) concentrations were measured at 110 wk of age. No significant differences were observed when feeding GM on egg production (EP), feed intake (FI) and feed conversion ratio (FCR). Supplementation of enzyme significantly reduced FI and improved FCR (P<0.05). Significant interaction was observed between enzyme and GM on egg weight (EW) and egg mass (EM) (P<0.05). Adding enzyme, decreased EW and EM in 4% GM diet but had diverse effect in control diet. The results of this study indicated that GM can be used in laying hens diets in the second-cycle of production up to 8% without any adverse effects on performance. The GM diets reduced serum triglyceride (P<0.05) and slightly egg yolk cholesterol concentrations. Supplementation of beta-mannanase enzyme significantly improved FCR by decreasing FI and also has significantly effect on decreasing egg yolk cholesterol and serum triglyceride (P<0.05). تفاصيل المقالة