Effects of Different Levels of Guar Meal and β‐Mannanase on Performance, Yolk Cholesterol Concentration and Blood Lipid Parameters of Laying Hens in Second‐Cycle of Production

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 pro-duction (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).