To assess effects of dietary inclusion of guar meal (GM) supplemented with a commercial enzyme product with main activity of β-mannanase on egg quality characteristics and blood parameters of laying hens, 144 Lohmann LSL-Lite hens were divided in 24 cages (n=6). Hens in 4 cages (replicates) were randomly assigned to feed on one of the six experimental diets. Based on a 3×2 factorial arrangement, six iso-caloric and iso-nitrogenous diets (ME=2720 kcal/kg and CP=145.8 g/kg) including three levels of guar meal (0.0, 25 and 50.0 g kg-1) with and without enzyme (Hemicell®, 0.0 and 0.4 g kg-1) were formulated. To determine blood biochemical parameters and differentiable count of white blood cells, one hen per replicate was bled via wing vein on day 35 of trial. Collected data was analyzed based on completely randomized design using GLM procedure of SAS. Adding GM to diet of laying hens did not significant effect on egg traits including egg index, yolk index, Haugh unit, egg shell weight and thickness. Diet enzyme supplementation decreased yolk index and egg shell thickness. Interactions between diet GM inclusion and enzyme supplementation on white blood cell count and plasma level of IgG were not statistically significant. There was no significant effect of diet GM inclusion on white blood cell count and plasma level of IgG. Enzyme supplementation decreased the blood counts of heterophill and basophill and increased lymphocyte. None of the blood biochemical parameters except for cholesterol was affected by diet GM inclusion and enzyme supplementation. Adding GM to diet of laying hens increased the serum level of cholesterol.
