Effects of Dietary Inclusion of Guar Meal Supplemented by β-Mannanase on Performance of Laying Hens, Egg Quality Characteristics and Diacritical Counts of White Blood Cells

Problem statement: Using Guar Meal (GM) in poultry diets has being limited because of having β-mannan, one of the Nonstarch Polysaccharides (NSP). In this study we try evaluating effects of enzyme supplementation of GM-included diets on productive performance of laying hens. Approach: A total number of 144 Lohmann LSL-Lite hens were divided in 24 cages (n = 6). Based on a 3 × 2 factorial arrangement of treatments, six iso-caloric and iso-nitrogenous diets including 3 levels of GM (0.0, 35.0 and 70.0 g kg) with and without enzyme (Hemicell® a β-mannanase-based enzyme, 0.0 and 0.6 g kg) were assigned to hens in 4 cages (replicates). Data was analyzed based on completely randomized design using GLM procedure of SAS. Results: Dietary GM inclusion significantly affected on Egg Production (EP) on weeks 2, 4 and 6 as well as the overall trail period. Hens fed the GM-included diets did have decreased EP compared to hens fed the control diet. Almost the same trend was observed in terms of Egg Mass (EM); so that hens fed the GM-included diets showed decreased EM compared to the hens fed the control diet. Enzyme supplementation did not have significant effect on EP in the present experiment, but EM was significantly improved in the hens fed the β-mannanase-supplemented diets on weeks 3, 6 and the overall experimental period. Dietary inclusion GM increased Feed Conversion Ratio (FCR) of laying hens compared to the hens fed the control diets on weeks 2, 4, 6 and overall trial period. Conclusion/Recommendations: Including GM in laying hens’ diets more than 3% may decrease productive performance. Supplementing cornsoybean or corn-soybean-GM diets by β-mannanase would have beneficial effects on performance of hens especially in terms of FCR and EP.


INTRODUCTION
Guar Meal (GM), a relatively inexpensive high protein meal, produced as a by-product of guar gum manufacture. The protein content of GM ranges between 33-60% depending on fraction type. GM results from combinations of two fractions, the germ and hull. The germ and hull constitute approximately 44 and 21% of the guar bean, respectively. However, the germ and hull proportions of the guar bean are not consistent with the relative amounts of the fractions mixed in guar meal. Also, the degree of contamination of the germ and hull fractions with guar gum is not equivalent within these proportions when mixed into commercial GM. Guar gum residue contained in the meal increases the viscosity of digesta, thereby decreasing growth and feed efficiency.
Improving poultry performance by dietary manipulation has been the goal of nutritionists. Modification NRC nutrient recommendations (Maroufyan et al., 2010;Fanooci and Torki, 2010), using feed additives like enzymes (Zangiabadi and Torki, 2010), organic acids (Mahdavi and Torki, 2009) or medicinal plants (Ghasemi et al., 2010;Najafi and Torki, 2010) has been reported by other researchers. A patented enzyme product (β-mannanase, Hemicell) has been shown to improve feed conversion in cornsoybean diets fed to layers (Zangiabadi and Torki, 2009). The mechanism of β-mannanase is to degrade βmannan, which is an antinutritional factor existing in many legumes, including soybean and canola meals. Dietary inclusion of Hemicell has improved broiler performance of broilers fed corn-soybean meal-or corn-soybean meal-palm date-included diets (Zangiabadi and Torki, 2010).
The objectives of the present study were to investigate effects of dietary including graded levels of GM supplemented by enzyme on productive performance of laying hens, egg quality characteristics and diacritical counts of white blood cells.

MATERIALS AND METHODS
A total number of 144 Lohmann LSL-Lite hens were divided in 24 cages (n = 6) with almost equal distribution of average body weight and egg production among cages. Hens in 4 cages (replicates) were assigned to feed on one the 6 experimental diets. Based on a 3×2 factorial arrangement of treatments, 6 isocaloric and iso-nitrogenous diets (ME =2720 Kcal kg −1 and CP =145 g kg −1 ) including GM (0.0, 35.0 and 70.0 g kg −1 ) and enzyme (0.0 and 0.6 g kg −1 ) were formulated (Table 1). Collected data of Feed Intake (FI), Egg Production (EP), Egg Mass (EM) and calculated Feed Conversion Ratio (FCR) during 6 week trial period was analyzed based on completely randomized design using GLM procedure of SAS.

RESULTS
Effects of dietary GM inclusion and enzyme supplementation on EP, FI, FCR, Egg Weight (EW) and EM during experimental period (6 weeks) are presented in Table 1-6, respectively. There was no interaction between dietary GM inclusion and enzyme supplementation on any of productive performance and egg quality traits (p>0.05). Dietary GM inclusion significantly affected on EP on weeks 2, 4 and 6 as well as the overall trail period (weeks 1-6). Hens fed the GM-included diets did have decreased EP compared to hens fed the control diet. Almost the same trend was observed in terms of EM; so that hens fed the GMincluded diets showed decreased EM compared to hens fed the control diet (Table 6).  The vitamin and mineral premix provide the following quantities per kilogram of diet: vitamin A, 10,000 IU (all-trans-retinal); cholecalciferol, 2,000 IU; vitamin E, 20 IU (α-tocopheryl); vitamin K3, 3.0 mg; riboflavin, 18.0 mg; niacin, 50 mg; D-calcium pantothenic acid, 24 mg; choline chloride, 450 mg; vitamin B12, 0.02 mg; folic acid, 3.0 mg; manganese, 110 mg; zinc, 100 mg; iron, 60 mg; copper, 10 mg; iodine, 100 mg; selenium, 0.2 mg and antioxidant, 250 mg Table 2: Effects of dietary guar meal inclusion (0, 35.0 and 70 g kg −1 ) and enzyme supplementation (0.0 and 0.6 g kg −1 ) on egg production (%) Egg production (%) Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Table 3: Effects of dietary guar meal inclusion (0, 35.0 and 70 g kg −1 ) and enzyme supplementation (0.0 and 0.6 g kg −1 ) on feed intake Week 1 Week 2 Week 3 Week 4 Week 5 Week 6   Although, enzyme supplementation did not have significant effect on EP in the present experiment (Table 2), EM was significantly improved in hens fed the β-mannanase-supplemented diets on weeks 3, 6 and the overall experimental period (weeks 1-6, Table 6). Hens fed the GM-included diets had decreased FI compared to hens fed the control diet on week 1 of the trial; however, FI of hens during week 2-6 did not significantly affected by dietary GM inclusion or enzyme supplementation (Table 3). As it is presented in Table 4, including GM to diets increased FCR of laying hens compared to hens fed the control diets on weeks 2, 4, 6 and overall trial period (weeks 1-6). In the present study, dietary supplementation by β-mannanase improved FCR on weeks 3, 6 and the overall experimental period. The results of dietary treatment on the measured egg quality characteristics were shown in Table 6. Table 4: Effects of dietary guar meal inclusion (0, 35.0 and 70 g kg −1 ) and enzyme supplementation (0.0 and 0.6 g kg −1 ) on Feed Conversion
Enzyme supplementation did not have any beneficial effects on the measured egg traits in this study.
The results of dietary effects on the white blood cell count in the present trial are shown in Table 8. There was no significant effect of dietary treatment on the white blood cell count.  Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Table 7: Effects of dietary guar meal inclusion (0, 35.0 and 70 g kg −1 ) and enzyme supplementation (0.0 and 0.6 g kg −1 ) on egg quality characteristics (egg index, yolk index, Haugh unit, egg shell weight and egg shell thickness) Egg quality characteristics