Performance, egg quality, nutrient digestibility, and excreta microbiota shedding in laying hens fed corn-soybean-meal-wheat-based diets supplemented with xylanase

Performance, egg quality, nutrient digestibility, and excreta microbiota shedding in laying hens... ABSTRACT The aim of this study was to evaluate the effects of dietary levels of xylanase on production performance, egg quality, nutrient digestibility, and excreta microbiota shedding of laying hens in a 12-week trial. Two-hundred-forty Hy-Line brown laying hens (44 wk old) were distributed according to a randomized block experimental design into one of 4 dietary treatments with 10 replicates of 6 birds each. The 4 dietary treatments were corn-soybean-meal-wheat-based diets supplemented with 0, 225, 450, or 900 U/kg xylanase. Daily feed intake, egg production, egg weight, egg mass, feed conversion ratio, and damaged egg rate showed no significant response to increasing xylanase supplementation during any phase (P > 0.05). No significant responses were observed for apparent total tract digestibility of dry matter, nitrogen, or gross energy (P > 0.05). A significant linear increase to increasing xylanase supplementation was seen for lactic acid bacteria numbers, although coliforms and Salmonella counts were not affected. Increasing the dietary xylanase resulted in a significant linear increase in eggshell thickness in wk 3, 6, 9, and 12 (P < 0.05). In addition, a significant linear increase occurred for Haugh unit and albumen height in wk 12 (P < 0.05). In summary, the inclusion of xylanase in corn-soybean-meal-wheat-based diets increased eggshell thickness, Haugh unit, albumen height, and excreta lactic acid bacteria count but had no effect on production performance or nutrient digestibility. INTRODUCTION Corn and wheat are dominant energy sources used in poultry diets worldwide because of their high energy content (Cufadar et al., 2010; Gatrell et al., 2014). Soybean meal (SBM) is the main protein ingredient for poultry diets (Laudadio and Tufarelli, 2011). However, the presence of non-starch polysaccharides (NSP) in wheat, corn, and SBM may negatively affect nutrient utilization and performance of poultry (Mathlouthi et al., 2003; Yegani and Korver, 2008; Kiarie et al., 2014; Jahanian and Golshadi, 2015). Previous studies demonstrated that around 5.2% arabinoxylan is present in corn, 8.1% arabinoxylan is present in wheat, and 3.3% arabinoxylan is present in SBM (Choct, 1997; Knudsen, 1997). Recently, the use of dietary enzymes in commercial laying hen diets has become a common practice (Slominski, 2011; Shastak et al., 2015; Erdaw et al., 2016; Gadde et al., 2017). Exogenous xylanases may improve intestinal microbial balance, nutrient digestibility, and performance in high soluble NSP (wheat-based) diets (Mathlouthi et al., 2002; Silversides et al., 2006; Mirzaie et al., 2012; Swiatkiewicz et al., 2016). However, there is increasing evidence suggesting that xylanase supplementation can improve the nutritional value of corn-SBM-based diets. Mathlouthi et al. (2003) suggested that multi-enzymes (xylanase and β-glucanase) exhibited beneficial effects on feed conversion ratio of hens fed not only a wheat-barley-based diet but also a maize-SBM-based diet. Bobeck et al. (2014) observed that dietary supplementation with xylanase enhanced egg mass, egg production, and feed efficiency in laying hens fed corn-SBM-dried distillers’ grains with solubles-based diets. Additionally, in laying quails, Bayram et al. (2008) found that inclusion of xylanase in corn-SBM-based diets improved feed conversion ratio. We hypothesized that the xylanase addition in a corn-wheat-SBM-based diet would improve nutrient digestibility and production performance in laying hens. Therefore, the current experiment was designed to study the effects of xylanase supplementation on production performance, egg quality, nutrient digestibility, and excreta microbiota shedding in laying hens fed a corn-wheat-SBM-based diet. MATERIALS AND METHODS The experimental protocols used in the study were approved by the Animal Care and Use Committee of Dankook University. Xylanase Source The xylanase used in this study was Nutrase Xyla (Nutrex Nv, Lille, Belgium), derived from fermentation by Bacillus subtilis. It is a specific endo-1, 4-β-xylanase (IUB: EC 3.2.1.8; 9,000 U/g) with an optimal activity at neutral pH. Xylanase activity was assayed using Xylazyme AX tablets (Megazyme International Ltd., Bray, Ireland). Experimental Birds and Design A total of 240 Hy-Line brown laying hens (44 wk of age) was randomly assigned to one of 4 treatments with 10 replications and 6 hens per replication (one hen/cage) in a 12-week feeding experiment. The 4 dietary treatments were corn-SBM-wheat-based diets supplemented with 0, 225, 450, or 900 U/kg xylanase. The composition of the basal diet is shown in Table 1 and was formulated according to the recommendations provided in NRC (1994). The hens were housed in a windowless and environmentally controlled room that was maintained at 23°C. Sixteen h (0500 to 2100 h) of artificial lighting were provided daily. All hens were housed individually in cages (38 cm width × 50 cm length × 40 cm height). Feed and water were provided for ad libitum consumption, and all diets were presented in mash form. Table 1. Composition and nutrient content of basal diet for laying hens (as-fed basis). Item Weeks 1 to 12 Ingredients, %  Corn 50.40  Soybean meal 18.70  Wheat 10.00  Corn gluten meal 2.00  Wheat bran 5.00  Animal fat 4.40  Limestone 7.50  Dicalcium phosphate 1.40  Salt 0.30  DL- Methionine 0.10  Vitamin premix1 0.10  Trace mineral premix2 0.10 Calculated nutrient content, %  Metabolizable energy, kcal/kg 2904  Crude protein 15.02  Calcium 3.25  Available phosphorus 0.38  Digestible lysine 0.66  Digestible methionine + cysteine 0.56  Digestible methionine 0.38  Digestible threonine 0.44  Digestible tryptophan 0.16 Analyzed nutrient content, %  Crude protein 15.09  Lysine 0.75  Calcium 3.22  Total phosphorus 0.58 Item Weeks 1 to 12 Ingredients, %  Corn 50.40  Soybean meal 18.70  Wheat 10.00  Corn gluten meal 2.00  Wheat bran 5.00  Animal fat 4.40  Limestone 7.50  Dicalcium phosphate 1.40  Salt 0.30  DL- Methionine 0.10  Vitamin premix1 0.10  Trace mineral premix2 0.10 Calculated nutrient content, %  Metabolizable energy, kcal/kg 2904  Crude protein 15.02  Calcium 3.25  Available phosphorus 0.38  Digestible lysine 0.66  Digestible methionine + cysteine 0.56  Digestible methionine 0.38  Digestible threonine 0.44  Digestible tryptophan 0.16 Analyzed nutrient content, %  Crude protein 15.09  Lysine 0.75  Calcium 3.22  Total phosphorus 0.58 1Provided per kilogram of diet: 12,500 IU vitamin A; 2,500 IU vitamin D3; 20 mg vitamin E; 2 mg vitamin K3; 1 mg vitamin B1; 5 mg vitamin B2; 1 mg vitamin B6; 15 μg vitamin B12; 1 mg folic acid; 35 mg niacin; 10 mg Ca-pantothenate and 50 μg biotin. 2Provided per kilogram of diet: 8 mg Mn (as MnO2); 60 mg Zn (as ZnSO4); 5 mg Cu (as CuSO4·5H2O); 40 mg Fe (as FeSO4·7H2O); 0.3 mg Co (as CoSO4·5H2O); 1.5 mg I (as KI) and 0.15 mg Se (as Na2SeO3·5H2O). View Large Table 1. Composition and nutrient content of basal diet for laying hens (as-fed basis). Item Weeks 1 to 12 Ingredients, %  Corn 50.40  Soybean meal 18.70  Wheat 10.00  Corn gluten meal 2.00  Wheat bran 5.00  Animal fat 4.40  Limestone 7.50  Dicalcium phosphate 1.40  Salt 0.30  DL- Methionine 0.10  Vitamin premix1 0.10  Trace mineral premix2 0.10 Calculated nutrient content, %  Metabolizable energy, kcal/kg 2904  Crude protein 15.02  Calcium 3.25  Available phosphorus 0.38  Digestible lysine 0.66  Digestible methionine + cysteine 0.56  Digestible methionine 0.38  Digestible threonine 0.44  Digestible tryptophan 0.16 Analyzed nutrient content, %  Crude protein 15.09  Lysine 0.75  Calcium 3.22  Total phosphorus 0.58 Item Weeks 1 to 12 Ingredients, %  Corn 50.40  Soybean meal 18.70  Wheat 10.00  Corn gluten meal 2.00  Wheat bran 5.00  Animal fat 4.40  Limestone 7.50  Dicalcium phosphate 1.40  Salt 0.30  DL- Methionine 0.10  Vitamin premix1 0.10  Trace mineral premix2 0.10 Calculated nutrient content, %  Metabolizable energy, kcal/kg 2904  Crude protein 15.02  Calcium 3.25  Available phosphorus 0.38  Digestible lysine 0.66  Digestible methionine + cysteine 0.56  Digestible methionine 0.38  Digestible threonine 0.44  Digestible tryptophan 0.16 Analyzed nutrient content, %  Crude protein 15.09  Lysine 0.75  Calcium 3.22  Total phosphorus 0.58 1Provided per kilogram of diet: 12,500 IU vitamin A; 2,500 IU vitamin D3; 20 mg vitamin E; 2 mg vitamin K3; 1 mg vitamin B1; 5 mg vitamin B2; 1 mg vitamin B6; 15 μg vitamin B12; 1 mg folic acid; 35 mg niacin; 10 mg Ca-pantothenate and 50 μg biotin. 2Provided per kilogram of diet: 8 mg Mn (as MnO2); 60 mg Zn (as ZnSO4); 5 mg Cu (as CuSO4·5H2O); 40 mg Fe (as FeSO4·7H2O); 0.3 mg Co (as CoSO4·5H2O); 1.5 mg I (as KI) and 0.15 mg Se (as Na2SeO3·5H2O). View Large Production Performance The number and weight of eggs laid were recorded daily, and feed intake was recorded weekly on a replication basis. Feed conversion ratio was calculated as gram of total feed intake per hen/gram of total egg mass per hen. The egg production was expressed as an average hen-day production. Egg mass was calculated by multiplying egg weight by egg production. The collected eggs were classified as either normal or damaged for calculating the damaged egg ratio. The damaged eggs included broken eggs, cracked eggs, and shell-less eggs. Egg Quality Parameters At the beginning of the experiment, and then at 3-week intervals, a total of 30 eggs (3 eggs per replication) with the exception of damaged eggs was randomly collected at 1700 h from each treatment and used to determine the egg quality at 2000 h the same day. Eggshell breaking strength was evaluated using an eggshell force gauge model II (Robotmation Co., Ltd., Tokyo, Japan). A dial pipe gauge (Ozaki MFG. Co., Ltd., Tokyo, Japan) was employed for measurements of the eggshell thickness, which was determined on the basis of the average thickness of the rounded end, pointed end, and the middle of the egg, excluding the inner membrane. An eggshell color fan was used to visually determine the eggshell color (DSM, Basel, Switzerland). Yolk color, yolk height, and Haugh unit were evaluated using an egg multi-tester (Touhoku Rhythm Co. Ltd., Tokyo, Japan). The measurements regarding egg quality were analyzed by one observer who was blind to the treatment. Apparent Total Tract Digestibility At 11 wk of the experiment, chromium oxide (0.2%) was included in the experimental diets as an indigestible marker to determine the apparent total tract digestibility (ATTD) of dry matter (DM), nitrogen (N), and gross energy (GE). During the last 3 d of the experiment, fresh excreta samples from each replication were collected and stored at –20°C until subsequent analysis was conducted. Contaminations such as feathers and scales were removed from the excreta. For chemical analysis, excreta samples were oven-dried at 60°C for 72 h, after which diets and excreta samples were ground to pass through a 1.0-mm screen for analysis of DM (method 930.15) and N (method 984.13) using the AOAC (2007) procedures. Gross energy was determined by measuring the heat of combustion in the samples, using a bomb calorimeter (Parr 6100; Parr Instrument Co., Moline, IL). Chromium was analyzed via UV absorption spectrophotometry (UV-1201, Shimadzu Corp., Kyoto, Japan), according to the method described by Williams et al. (1962). The ATTD was then calculated using the following formula: \begin{eqnarray*} {\rm{ATTD}}\left( \% \right) &=& \left[ {1 - \{ \left( {{\rm{Ne}} \times {\rm{Cf}}} \right)/\left( {{\rm{Nf}} \times {\rm{Ce}}} \right)\} } \right] \times 100, \end{eqnarray*} Where: Ne = nutrient concentration in excreta (% DM), Nf = nutrient concentration in feed (% DM), Cf = chromium concentration in feed (% DM), and Ce = chromium concentration in excreta (% DM). Excreta Microbial Shedding At the end of the experiment, excreta samples were randomly collected from 10 layers (one layer per replication) from each treatment, and then placed on ice for transportation to the laboratory. One gram of the composite excreta sample from each replication was diluted with 9 mL of 1% peptone broth (Becton, Dickinson and Co., Rutherford, NJ) and then homogenized. Viable counts of bacteria in the excreta samples were then determined by plating serial 10-fold dilutions (in 10 g/L peptone solution) onto MacConkey agar plates (Difco Laboratories, Detroit, MI), lactobacilli medium III agar plates (Medium 638; DSMZ, Braunschweig, Germany), and Salmonella-Shigella agar plates to isolate coliforms, lactic acid bacteria, and Salmonella, respectively. The lactobacilli medium III agar plates were then incubated for 48 h at 37°C under anaerobic conditions. The MacConkey and Salmonella-Shigella agar plates were both incubated for 24 h at 37°C. The microbial colonies were counted immediately after removal from the incubator. The microbial populations were finally expressed as log10 colony-forming units per gram of excreta. Statistical Analyses All data were subjected to statistical analysis in a randomized complete block design using the General Linear Model procedure (SAS Institute, Cary, NC). Replication (n = 10) was used as the experimental unit. Orthogonal contrasts were used to examine the linear, quadratic, and cubic effects in response to increasing the dietary supplementation of xylanase. The results were presented as means and pooled standard error of the mean. Probability values less than 0.05 were considered significant. RESULTS Productive Performance and Egg Quality The effects of xylanase supplementation in corn-wheat-SBM-based diets on productive performance are presented in Table 2. Throughout the experiment, daily feed intake, egg production, egg weight, egg mass, feed conversion ratio, and damaged eggs rate were not affected by xylanase supplementation. No significant effects of xylanase supplementation were found for eggshell strength or shell color throughout the experiment (P > 0.05; Table 3). There was a significant linear increase (P < 0.05) in eggshell thickness in response to increasing xylanase supplementation in wk 3, 6, 9, and 12. Additionally, as xylanase supplementation increased, Haugh unit and albumen height increased (P < 0.05) linearly in wk 12. Table 2. Effects of xylanase supplementation on production performance in laying hens from 44 to 56 wk of age. Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Weeks 1 to 3  Daily feed intake, g/d/hen 108.71 106.29 106.86 106.14 0.91 0.091 0.355 0.302  Egg production, % 89.80 89.48 90.99 90.70 0.98 0.347 0.989 0.415  Egg weight, g 65.78 65.79 65.75 65.89 1.31 0.961 0.958 0.969  Egg mass, g/d/hen 59.06 58.84 59.81 59.76 1.25 0.588 0.950 0.694  FCR1, g feed/g egg 1.84 1.81 1.80 1.78 0.05 0.349 0.873 0.965  Damaged egg ratio, % 0.57 0.43 0.20 0.33 0.37 0.235 0.617 0.620 Weeks 4 to 6  Daily feed intake, g/d/hen 108.00 108.71 109.71 108.00 0.64 0.730 0.070 0.305  Egg production, % 89.41 89.34 89.83 90.03 0.94 0.581 0.885 0.844  Egg weight, g 65.21 65.69 65.95 66.13 1.37 0.628 0.912 0.984  Egg mass, g/d/hen 58.24 58.70 59.25 59.59 1.36 0.459 0.963 0.959  FCR1, g feed/g egg 1.86 1.86 1.85 1.82 0.05 0.554 0.743 0.861  Damaged egg ratio, % 0.33 0.20 0.23 0.00 0.26 0.499 0.287 0.742 Weeks 7 to 9  Daily feed intake, g/d/hen 109.71 108.86 108.43 109.71 0.79 0.904 0.185 0.717  Egg production, % 87.70 88.14 88.54 89.03 1.15 0.399 0.983 0.978  Egg weight, g 64.49 67.13 65.58 64.94 1.63 0.982 0.327 0.498  Egg mass, g/d/hen 56.58 57.17 58.09 57.82 1.74 0.733 0.420 0.570  FCR1, g feed/g egg 1.95 1.85 1.88 1.91 0.06 0.771 0.342 0.647  Damaged egg ratio, % 0.00 0.23 0.33 0.43 0.28 0.320 0.604 0.562 Weeks 9 to 12  Daily feed intake, g/d/hen 111.71 109.71 109.43 109.29 1.03 0.113 0.376 0.736  Egg production, % 86.24 86.81 87.34 87.82 1.34 0.390 0.970 0.997  Egg weight, g 64.85 65.03 65.15 65.45 1.30 0.746 0.965 0.967  Egg mass, g/d/hen 55.99 56.44 56.87 57.49 1.48 0.465 0.954 0.974  FCR1, g feed/g egg 2.01 1.95 1.93 1.91 0.06 0.253 0.743 0.866  Damaged egg ratio, % 0.37 0.33 0.33 0.10 0.31 0.460 0.686 0.383 Weeks 1 to 12  Daily feed intake, g/d/hen 109.54 108.39 108.61 108.29 0.49 0.118 0.408 0.394  Egg production, % 88.29 88.44 89.17 89.39 0.68 0.194 0.964 0.727  Egg weight, g 65.60 65.61 65.90 65.08 0.68 0.683 0.551 0.648  Egg mass, g/d/hen 57.47 58.29 58.51 58.66 0.75 0.268 0.663 0.872  FCR1, g feed/g egg 1.91 1.86 1.86 1.85 0.03 0.165 0.495 0.692  Damaged egg ratio, % 0.32 0.30 0.28 0.22 0.09 0.421 0.731 0.989 Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Weeks 1 to 3  Daily feed intake, g/d/hen 108.71 106.29 106.86 106.14 0.91 0.091 0.355 0.302  Egg production, % 89.80 89.48 90.99 90.70 0.98 0.347 0.989 0.415  Egg weight, g 65.78 65.79 65.75 65.89 1.31 0.961 0.958 0.969  Egg mass, g/d/hen 59.06 58.84 59.81 59.76 1.25 0.588 0.950 0.694  FCR1, g feed/g egg 1.84 1.81 1.80 1.78 0.05 0.349 0.873 0.965  Damaged egg ratio, % 0.57 0.43 0.20 0.33 0.37 0.235 0.617 0.620 Weeks 4 to 6  Daily feed intake, g/d/hen 108.00 108.71 109.71 108.00 0.64 0.730 0.070 0.305  Egg production, % 89.41 89.34 89.83 90.03 0.94 0.581 0.885 0.844  Egg weight, g 65.21 65.69 65.95 66.13 1.37 0.628 0.912 0.984  Egg mass, g/d/hen 58.24 58.70 59.25 59.59 1.36 0.459 0.963 0.959  FCR1, g feed/g egg 1.86 1.86 1.85 1.82 0.05 0.554 0.743 0.861  Damaged egg ratio, % 0.33 0.20 0.23 0.00 0.26 0.499 0.287 0.742 Weeks 7 to 9  Daily feed intake, g/d/hen 109.71 108.86 108.43 109.71 0.79 0.904 0.185 0.717  Egg production, % 87.70 88.14 88.54 89.03 1.15 0.399 0.983 0.978  Egg weight, g 64.49 67.13 65.58 64.94 1.63 0.982 0.327 0.498  Egg mass, g/d/hen 56.58 57.17 58.09 57.82 1.74 0.733 0.420 0.570  FCR1, g feed/g egg 1.95 1.85 1.88 1.91 0.06 0.771 0.342 0.647  Damaged egg ratio, % 0.00 0.23 0.33 0.43 0.28 0.320 0.604 0.562 Weeks 9 to 12  Daily feed intake, g/d/hen 111.71 109.71 109.43 109.29 1.03 0.113 0.376 0.736  Egg production, % 86.24 86.81 87.34 87.82 1.34 0.390 0.970 0.997  Egg weight, g 64.85 65.03 65.15 65.45 1.30 0.746 0.965 0.967  Egg mass, g/d/hen 55.99 56.44 56.87 57.49 1.48 0.465 0.954 0.974  FCR1, g feed/g egg 2.01 1.95 1.93 1.91 0.06 0.253 0.743 0.866  Damaged egg ratio, % 0.37 0.33 0.33 0.10 0.31 0.460 0.686 0.383 Weeks 1 to 12  Daily feed intake, g/d/hen 109.54 108.39 108.61 108.29 0.49 0.118 0.408 0.394  Egg production, % 88.29 88.44 89.17 89.39 0.68 0.194 0.964 0.727  Egg weight, g 65.60 65.61 65.90 65.08 0.68 0.683 0.551 0.648  Egg mass, g/d/hen 57.47 58.29 58.51 58.66 0.75 0.268 0.663 0.872  FCR1, g feed/g egg 1.91 1.86 1.86 1.85 0.03 0.165 0.495 0.692  Damaged egg ratio, % 0.32 0.30 0.28 0.22 0.09 0.421 0.731 0.989 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 2. Effects of xylanase supplementation on production performance in laying hens from 44 to 56 wk of age. Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Weeks 1 to 3  Daily feed intake, g/d/hen 108.71 106.29 106.86 106.14 0.91 0.091 0.355 0.302  Egg production, % 89.80 89.48 90.99 90.70 0.98 0.347 0.989 0.415  Egg weight, g 65.78 65.79 65.75 65.89 1.31 0.961 0.958 0.969  Egg mass, g/d/hen 59.06 58.84 59.81 59.76 1.25 0.588 0.950 0.694  FCR1, g feed/g egg 1.84 1.81 1.80 1.78 0.05 0.349 0.873 0.965  Damaged egg ratio, % 0.57 0.43 0.20 0.33 0.37 0.235 0.617 0.620 Weeks 4 to 6  Daily feed intake, g/d/hen 108.00 108.71 109.71 108.00 0.64 0.730 0.070 0.305  Egg production, % 89.41 89.34 89.83 90.03 0.94 0.581 0.885 0.844  Egg weight, g 65.21 65.69 65.95 66.13 1.37 0.628 0.912 0.984  Egg mass, g/d/hen 58.24 58.70 59.25 59.59 1.36 0.459 0.963 0.959  FCR1, g feed/g egg 1.86 1.86 1.85 1.82 0.05 0.554 0.743 0.861  Damaged egg ratio, % 0.33 0.20 0.23 0.00 0.26 0.499 0.287 0.742 Weeks 7 to 9  Daily feed intake, g/d/hen 109.71 108.86 108.43 109.71 0.79 0.904 0.185 0.717  Egg production, % 87.70 88.14 88.54 89.03 1.15 0.399 0.983 0.978  Egg weight, g 64.49 67.13 65.58 64.94 1.63 0.982 0.327 0.498  Egg mass, g/d/hen 56.58 57.17 58.09 57.82 1.74 0.733 0.420 0.570  FCR1, g feed/g egg 1.95 1.85 1.88 1.91 0.06 0.771 0.342 0.647  Damaged egg ratio, % 0.00 0.23 0.33 0.43 0.28 0.320 0.604 0.562 Weeks 9 to 12  Daily feed intake, g/d/hen 111.71 109.71 109.43 109.29 1.03 0.113 0.376 0.736  Egg production, % 86.24 86.81 87.34 87.82 1.34 0.390 0.970 0.997  Egg weight, g 64.85 65.03 65.15 65.45 1.30 0.746 0.965 0.967  Egg mass, g/d/hen 55.99 56.44 56.87 57.49 1.48 0.465 0.954 0.974  FCR1, g feed/g egg 2.01 1.95 1.93 1.91 0.06 0.253 0.743 0.866  Damaged egg ratio, % 0.37 0.33 0.33 0.10 0.31 0.460 0.686 0.383 Weeks 1 to 12  Daily feed intake, g/d/hen 109.54 108.39 108.61 108.29 0.49 0.118 0.408 0.394  Egg production, % 88.29 88.44 89.17 89.39 0.68 0.194 0.964 0.727  Egg weight, g 65.60 65.61 65.90 65.08 0.68 0.683 0.551 0.648  Egg mass, g/d/hen 57.47 58.29 58.51 58.66 0.75 0.268 0.663 0.872  FCR1, g feed/g egg 1.91 1.86 1.86 1.85 0.03 0.165 0.495 0.692  Damaged egg ratio, % 0.32 0.30 0.28 0.22 0.09 0.421 0.731 0.989 Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Weeks 1 to 3  Daily feed intake, g/d/hen 108.71 106.29 106.86 106.14 0.91 0.091 0.355 0.302  Egg production, % 89.80 89.48 90.99 90.70 0.98 0.347 0.989 0.415  Egg weight, g 65.78 65.79 65.75 65.89 1.31 0.961 0.958 0.969  Egg mass, g/d/hen 59.06 58.84 59.81 59.76 1.25 0.588 0.950 0.694  FCR1, g feed/g egg 1.84 1.81 1.80 1.78 0.05 0.349 0.873 0.965  Damaged egg ratio, % 0.57 0.43 0.20 0.33 0.37 0.235 0.617 0.620 Weeks 4 to 6  Daily feed intake, g/d/hen 108.00 108.71 109.71 108.00 0.64 0.730 0.070 0.305  Egg production, % 89.41 89.34 89.83 90.03 0.94 0.581 0.885 0.844  Egg weight, g 65.21 65.69 65.95 66.13 1.37 0.628 0.912 0.984  Egg mass, g/d/hen 58.24 58.70 59.25 59.59 1.36 0.459 0.963 0.959  FCR1, g feed/g egg 1.86 1.86 1.85 1.82 0.05 0.554 0.743 0.861  Damaged egg ratio, % 0.33 0.20 0.23 0.00 0.26 0.499 0.287 0.742 Weeks 7 to 9  Daily feed intake, g/d/hen 109.71 108.86 108.43 109.71 0.79 0.904 0.185 0.717  Egg production, % 87.70 88.14 88.54 89.03 1.15 0.399 0.983 0.978  Egg weight, g 64.49 67.13 65.58 64.94 1.63 0.982 0.327 0.498  Egg mass, g/d/hen 56.58 57.17 58.09 57.82 1.74 0.733 0.420 0.570  FCR1, g feed/g egg 1.95 1.85 1.88 1.91 0.06 0.771 0.342 0.647  Damaged egg ratio, % 0.00 0.23 0.33 0.43 0.28 0.320 0.604 0.562 Weeks 9 to 12  Daily feed intake, g/d/hen 111.71 109.71 109.43 109.29 1.03 0.113 0.376 0.736  Egg production, % 86.24 86.81 87.34 87.82 1.34 0.390 0.970 0.997  Egg weight, g 64.85 65.03 65.15 65.45 1.30 0.746 0.965 0.967  Egg mass, g/d/hen 55.99 56.44 56.87 57.49 1.48 0.465 0.954 0.974  FCR1, g feed/g egg 2.01 1.95 1.93 1.91 0.06 0.253 0.743 0.866  Damaged egg ratio, % 0.37 0.33 0.33 0.10 0.31 0.460 0.686 0.383 Weeks 1 to 12  Daily feed intake, g/d/hen 109.54 108.39 108.61 108.29 0.49 0.118 0.408 0.394  Egg production, % 88.29 88.44 89.17 89.39 0.68 0.194 0.964 0.727  Egg weight, g 65.60 65.61 65.90 65.08 0.68 0.683 0.551 0.648  Egg mass, g/d/hen 57.47 58.29 58.51 58.66 0.75 0.268 0.663 0.872  FCR1, g feed/g egg 1.91 1.86 1.86 1.85 0.03 0.165 0.495 0.692  Damaged egg ratio, % 0.32 0.30 0.28 0.22 0.09 0.421 0.731 0.989 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 3. Effects of xylanase supplementation on egg quality in laying hens from 44 to 56 wk of age. Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Initial  Shell color 10.71 10.52 10.89 10.74 0.21 0.490 0.722 0.127  Eggshell strength, kg/cm2 3.88 3.86 3.89 3.88 0.03 0.169 0.676 0.433  Haugh Unit 90.61 91.03 90.44 90.73 1.11 0.993 0.431 0.952  Albumen height, mm 8.51 8.62 8.50 8.63 0.21 0.966 0.434 0.989  Yolk color 7.89 8.03 7.78 7.81 0.25 0.560 0.852 0.617  Eggshell thickness, 10−2 mm 46.60 46.52 46.67 46.71 0.52 0.479 0.335 0.904 Week 3  Shell color 10.22 10.13 10.12 10.45 0.40 0.548 0.573 0.892  Eggshell strength, kg/cm2 3.83 3.85 3.87 3.88 0.02 0.068 0.841 0.931  Haugh Unit 89.01 89.67 90.34 90.51 1.01 0.232 0.782 0.996  Albumen height, mm 8.23 8.31 8.44 8.52 0.19 0.183 0.880 0.987  Yolk color 8.3 8.29 8.31 8.10 0.34 0.731 0.719 0.909  Eggshell thickness, 10−2 mm 45.02 45.67 45.91 46.54 0.50 0.037 0.845 0.580 Week 6  Shell color 10.02 10.74 9.78 10.14 0.34 0.650 0.530 0.075  Eggshell strength, kg/cm2 3.83 3.85 3.86 3.88 0.02 0.065 0.903 0.925  Haugh Unit 89.84 90.77 91.19 91.81 0.98 0.143 0.872 0.868  Albumen height, mm 8.27 8.51 8.59 8.72 0.18 0.113 0.896 0.854  Yolk color 8.14 8.31 8.33 7.92 0.35 0.660 0.326 0.986  Eggshell thickness, 10−2 mm 44.82 45.67 46.04 46.81 0.59 0.021 0.955 0.631 Week 9  Shell color 10.67 10.21 10.33 10.44 0.36 0.617 0.403 0.708  Eggshell strength, kg/cm2 3.83 3.84 3.85 3.86 0.02 0.261 0.942 0.970  Haugh Unit 90.32 90.78 91.22 91.83 0.78 0.175 0.988 0.970  Albumen height, mm 8.41 8.45 8.62 8.67 0.14 0.100 0.996 0.905  Yolk color 8.24 8.21 8.20 8.33 0.32 0.875 0.880 0.982  Eggshell thickness, 10−2 mm 44.61 45.56 45.63 46.33 0.43 0.012 0.803 0.494 Week 12  Shell color 11.11 10.67 11.13 10.71 0.33 0.633 0.945 0.271  Eggshell strength, kg/cm2 3.86 3.88 3.89 3.92 0.03 0.118 0.862 0.950  Haugh Unit 89.92 91.79 92.70 93.22 0.66 0.001 0.406 0.894  Albumen height, mm 8.43 8.70 8.89 9.04 0.11 <0.001 0.383 0.975  Yolk color 8.30 8.11 8.31 8.34 0.28 0.941 0.868 0.631  Eggshell thickness,10−2 mm 45.27 45.77 46.07 46.43 0.36 0.014 0.854 0.874 Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Initial  Shell color 10.71 10.52 10.89 10.74 0.21 0.490 0.722 0.127  Eggshell strength, kg/cm2 3.88 3.86 3.89 3.88 0.03 0.169 0.676 0.433  Haugh Unit 90.61 91.03 90.44 90.73 1.11 0.993 0.431 0.952  Albumen height, mm 8.51 8.62 8.50 8.63 0.21 0.966 0.434 0.989  Yolk color 7.89 8.03 7.78 7.81 0.25 0.560 0.852 0.617  Eggshell thickness, 10−2 mm 46.60 46.52 46.67 46.71 0.52 0.479 0.335 0.904 Week 3  Shell color 10.22 10.13 10.12 10.45 0.40 0.548 0.573 0.892  Eggshell strength, kg/cm2 3.83 3.85 3.87 3.88 0.02 0.068 0.841 0.931  Haugh Unit 89.01 89.67 90.34 90.51 1.01 0.232 0.782 0.996  Albumen height, mm 8.23 8.31 8.44 8.52 0.19 0.183 0.880 0.987  Yolk color 8.3 8.29 8.31 8.10 0.34 0.731 0.719 0.909  Eggshell thickness, 10−2 mm 45.02 45.67 45.91 46.54 0.50 0.037 0.845 0.580 Week 6  Shell color 10.02 10.74 9.78 10.14 0.34 0.650 0.530 0.075  Eggshell strength, kg/cm2 3.83 3.85 3.86 3.88 0.02 0.065 0.903 0.925  Haugh Unit 89.84 90.77 91.19 91.81 0.98 0.143 0.872 0.868  Albumen height, mm 8.27 8.51 8.59 8.72 0.18 0.113 0.896 0.854  Yolk color 8.14 8.31 8.33 7.92 0.35 0.660 0.326 0.986  Eggshell thickness, 10−2 mm 44.82 45.67 46.04 46.81 0.59 0.021 0.955 0.631 Week 9  Shell color 10.67 10.21 10.33 10.44 0.36 0.617 0.403 0.708  Eggshell strength, kg/cm2 3.83 3.84 3.85 3.86 0.02 0.261 0.942 0.970  Haugh Unit 90.32 90.78 91.22 91.83 0.78 0.175 0.988 0.970  Albumen height, mm 8.41 8.45 8.62 8.67 0.14 0.100 0.996 0.905  Yolk color 8.24 8.21 8.20 8.33 0.32 0.875 0.880 0.982  Eggshell thickness, 10−2 mm 44.61 45.56 45.63 46.33 0.43 0.012 0.803 0.494 Week 12  Shell color 11.11 10.67 11.13 10.71 0.33 0.633 0.945 0.271  Eggshell strength, kg/cm2 3.86 3.88 3.89 3.92 0.03 0.118 0.862 0.950  Haugh Unit 89.92 91.79 92.70 93.22 0.66 0.001 0.406 0.894  Albumen height, mm 8.43 8.70 8.89 9.04 0.11 <0.001 0.383 0.975  Yolk color 8.30 8.11 8.31 8.34 0.28 0.941 0.868 0.631  Eggshell thickness,10−2 mm 45.27 45.77 46.07 46.43 0.36 0.014 0.854 0.874 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 3. Effects of xylanase supplementation on egg quality in laying hens from 44 to 56 wk of age. Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Initial  Shell color 10.71 10.52 10.89 10.74 0.21 0.490 0.722 0.127  Eggshell strength, kg/cm2 3.88 3.86 3.89 3.88 0.03 0.169 0.676 0.433  Haugh Unit 90.61 91.03 90.44 90.73 1.11 0.993 0.431 0.952  Albumen height, mm 8.51 8.62 8.50 8.63 0.21 0.966 0.434 0.989  Yolk color 7.89 8.03 7.78 7.81 0.25 0.560 0.852 0.617  Eggshell thickness, 10−2 mm 46.60 46.52 46.67 46.71 0.52 0.479 0.335 0.904 Week 3  Shell color 10.22 10.13 10.12 10.45 0.40 0.548 0.573 0.892  Eggshell strength, kg/cm2 3.83 3.85 3.87 3.88 0.02 0.068 0.841 0.931  Haugh Unit 89.01 89.67 90.34 90.51 1.01 0.232 0.782 0.996  Albumen height, mm 8.23 8.31 8.44 8.52 0.19 0.183 0.880 0.987  Yolk color 8.3 8.29 8.31 8.10 0.34 0.731 0.719 0.909  Eggshell thickness, 10−2 mm 45.02 45.67 45.91 46.54 0.50 0.037 0.845 0.580 Week 6  Shell color 10.02 10.74 9.78 10.14 0.34 0.650 0.530 0.075  Eggshell strength, kg/cm2 3.83 3.85 3.86 3.88 0.02 0.065 0.903 0.925  Haugh Unit 89.84 90.77 91.19 91.81 0.98 0.143 0.872 0.868  Albumen height, mm 8.27 8.51 8.59 8.72 0.18 0.113 0.896 0.854  Yolk color 8.14 8.31 8.33 7.92 0.35 0.660 0.326 0.986  Eggshell thickness, 10−2 mm 44.82 45.67 46.04 46.81 0.59 0.021 0.955 0.631 Week 9  Shell color 10.67 10.21 10.33 10.44 0.36 0.617 0.403 0.708  Eggshell strength, kg/cm2 3.83 3.84 3.85 3.86 0.02 0.261 0.942 0.970  Haugh Unit 90.32 90.78 91.22 91.83 0.78 0.175 0.988 0.970  Albumen height, mm 8.41 8.45 8.62 8.67 0.14 0.100 0.996 0.905  Yolk color 8.24 8.21 8.20 8.33 0.32 0.875 0.880 0.982  Eggshell thickness, 10−2 mm 44.61 45.56 45.63 46.33 0.43 0.012 0.803 0.494 Week 12  Shell color 11.11 10.67 11.13 10.71 0.33 0.633 0.945 0.271  Eggshell strength, kg/cm2 3.86 3.88 3.89 3.92 0.03 0.118 0.862 0.950  Haugh Unit 89.92 91.79 92.70 93.22 0.66 0.001 0.406 0.894  Albumen height, mm 8.43 8.70 8.89 9.04 0.11 <0.001 0.383 0.975  Yolk color 8.30 8.11 8.31 8.34 0.28 0.941 0.868 0.631  Eggshell thickness,10−2 mm 45.27 45.77 46.07 46.43 0.36 0.014 0.854 0.874 Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Initial  Shell color 10.71 10.52 10.89 10.74 0.21 0.490 0.722 0.127  Eggshell strength, kg/cm2 3.88 3.86 3.89 3.88 0.03 0.169 0.676 0.433  Haugh Unit 90.61 91.03 90.44 90.73 1.11 0.993 0.431 0.952  Albumen height, mm 8.51 8.62 8.50 8.63 0.21 0.966 0.434 0.989  Yolk color 7.89 8.03 7.78 7.81 0.25 0.560 0.852 0.617  Eggshell thickness, 10−2 mm 46.60 46.52 46.67 46.71 0.52 0.479 0.335 0.904 Week 3  Shell color 10.22 10.13 10.12 10.45 0.40 0.548 0.573 0.892  Eggshell strength, kg/cm2 3.83 3.85 3.87 3.88 0.02 0.068 0.841 0.931  Haugh Unit 89.01 89.67 90.34 90.51 1.01 0.232 0.782 0.996  Albumen height, mm 8.23 8.31 8.44 8.52 0.19 0.183 0.880 0.987  Yolk color 8.3 8.29 8.31 8.10 0.34 0.731 0.719 0.909  Eggshell thickness, 10−2 mm 45.02 45.67 45.91 46.54 0.50 0.037 0.845 0.580 Week 6  Shell color 10.02 10.74 9.78 10.14 0.34 0.650 0.530 0.075  Eggshell strength, kg/cm2 3.83 3.85 3.86 3.88 0.02 0.065 0.903 0.925  Haugh Unit 89.84 90.77 91.19 91.81 0.98 0.143 0.872 0.868  Albumen height, mm 8.27 8.51 8.59 8.72 0.18 0.113 0.896 0.854  Yolk color 8.14 8.31 8.33 7.92 0.35 0.660 0.326 0.986  Eggshell thickness, 10−2 mm 44.82 45.67 46.04 46.81 0.59 0.021 0.955 0.631 Week 9  Shell color 10.67 10.21 10.33 10.44 0.36 0.617 0.403 0.708  Eggshell strength, kg/cm2 3.83 3.84 3.85 3.86 0.02 0.261 0.942 0.970  Haugh Unit 90.32 90.78 91.22 91.83 0.78 0.175 0.988 0.970  Albumen height, mm 8.41 8.45 8.62 8.67 0.14 0.100 0.996 0.905  Yolk color 8.24 8.21 8.20 8.33 0.32 0.875 0.880 0.982  Eggshell thickness, 10−2 mm 44.61 45.56 45.63 46.33 0.43 0.012 0.803 0.494 Week 12  Shell color 11.11 10.67 11.13 10.71 0.33 0.633 0.945 0.271  Eggshell strength, kg/cm2 3.86 3.88 3.89 3.92 0.03 0.118 0.862 0.950  Haugh Unit 89.92 91.79 92.70 93.22 0.66 0.001 0.406 0.894  Albumen height, mm 8.43 8.70 8.89 9.04 0.11 <0.001 0.383 0.975  Yolk color 8.30 8.11 8.31 8.34 0.28 0.941 0.868 0.631  Eggshell thickness,10−2 mm 45.27 45.77 46.07 46.43 0.36 0.014 0.854 0.874 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Apparent Total Tract Digestibility and Excreta Microbiota Shedding There were no significant differences in ATTD of DM, N, or GE due to the dietary treatments (P > 0.05; Table 4). A significant linear increase (P < 0.05) due to increasing xylanase supplementation was observed for lactic acid bacteria counts, but coliforms and Salmonella numbers were not affected (Table 5). Table 4. Effects of 12-week xylanase supplementation on apparent total tract digestibility in laying hens. Xylanase supplementation (U/kg) P-value Items, % 0 225 450 900 SEM1 L1 Q1 C1 Dry matter 73.11 73.65 73.71 73.75 0.97 0.654 0.802 0.919 Nitrogen 64.45 63.93 64.11 64.70 1.21 0.856 0.631 0.952 Gross energy 75.71 75.78 75.78 75.81 0.80 0.935 0.974 0.977 Xylanase supplementation (U/kg) P-value Items, % 0 225 450 900 SEM1 L1 Q1 C1 Dry matter 73.11 73.65 73.71 73.75 0.97 0.654 0.802 0.919 Nitrogen 64.45 63.93 64.11 64.70 1.21 0.856 0.631 0.952 Gross energy 75.71 75.78 75.78 75.81 0.80 0.935 0.974 0.977 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 4. Effects of 12-week xylanase supplementation on apparent total tract digestibility in laying hens. Xylanase supplementation (U/kg) P-value Items, % 0 225 450 900 SEM1 L1 Q1 C1 Dry matter 73.11 73.65 73.71 73.75 0.97 0.654 0.802 0.919 Nitrogen 64.45 63.93 64.11 64.70 1.21 0.856 0.631 0.952 Gross energy 75.71 75.78 75.78 75.81 0.80 0.935 0.974 0.977 Xylanase supplementation (U/kg) P-value Items, % 0 225 450 900 SEM1 L1 Q1 C1 Dry matter 73.11 73.65 73.71 73.75 0.97 0.654 0.802 0.919 Nitrogen 64.45 63.93 64.11 64.70 1.21 0.856 0.631 0.952 Gross energy 75.71 75.78 75.78 75.81 0.80 0.935 0.974 0.977 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 5. Effects of 12-week xylanase supplementation on excreta microbial shedding in laying hens. Xylanase supplementation (U/kg) P-value Items, log10 cfu/g 0 225 450 900 SEM1 L1 Q1 C1 Lactic acid bacteria 7.58 7.64 7.69 7.74 0.03 0.003 0.906 0.847 Coliforms 5.90 5.88 5.87 5.84 0.04 0.315 0.952 0.871 Salmonella 2.52 2.48 2.40 2.37 0.07 0.135 0.931 0.763 Xylanase supplementation (U/kg) P-value Items, log10 cfu/g 0 225 450 900 SEM1 L1 Q1 C1 Lactic acid bacteria 7.58 7.64 7.69 7.74 0.03 0.003 0.906 0.847 Coliforms 5.90 5.88 5.87 5.84 0.04 0.315 0.952 0.871 Salmonella 2.52 2.48 2.40 2.37 0.07 0.135 0.931 0.763 1C, cubic; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 5. Effects of 12-week xylanase supplementation on excreta microbial shedding in laying hens. Xylanase supplementation (U/kg) P-value Items, log10 cfu/g 0 225 450 900 SEM1 L1 Q1 C1 Lactic acid bacteria 7.58 7.64 7.69 7.74 0.03 0.003 0.906 0.847 Coliforms 5.90 5.88 5.87 5.84 0.04 0.315 0.952 0.871 Salmonella 2.52 2.48 2.40 2.37 0.07 0.135 0.931 0.763 Xylanase supplementation (U/kg) P-value Items, log10 cfu/g 0 225 450 900 SEM1 L1 Q1 C1 Lactic acid bacteria 7.58 7.64 7.69 7.74 0.03 0.003 0.906 0.847 Coliforms 5.90 5.88 5.87 5.84 0.04 0.315 0.952 0.871 Salmonella 2.52 2.48 2.40 2.37 0.07 0.135 0.931 0.763 1C, cubic; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large DISCUSSION Studies have shown improvements in production performance when xylanase was included in laying hen diets; but the effects of xylanase on the performance of laying hens is conflicting. Senkoylu et al. (2009) reported that inclusion of xylanase in corn-SBM-whole-wheat-based diets improved feed conversion ratio and egg production in Bovans White layers from 53 to 63 wk of age. Bobeck et al. (2014) indicated that supplementation of xylanase to corn-SBM-dried distillers’ grain-based diets improved egg production, egg mass, and feed efficiency in Hy-Line W-36 laying hens from 22 to 44 wk of age. Cufadar et al. (2010) determined the effects of adding 3 levels of xylanase (0, 100, and 200 mg/kg, respectively) to 5 experimental diets with 5 corn: wheat ratios (100:0, 75:25, 50:50, 25:75, and 0:100, respectively) in White Leghorn LSL laying hens (52 to 64 wk of age). However, Cufadar et al. (2010) observed that xylanase supplementation had no effect on performance, including egg production, egg weight, feed intake, and feed conversion ratio. In our study, there was no effect on daily feed intake, egg production, egg weight, egg mass, feed conversion ratio, or cracked-egg rate when xylanase was supplemented in diets during any phase, suggesting that inclusion of xylanase in corn-SBM-wheat-based diets did not affect productive performance in laying hens. The conflicting findings between different studies may be due to differences in the age and strain of laying hens, the differences in the concentrations of xylanase, and the differences in compositions of diets. Additionally, supplementation of xylanase alone or in combination with different enzymes also may contribute to the inconsistent results concerning the performance of laying hens. Mathlouthi et al. (2003) found that inclusion of a multi-enzyme preparation containing xylanase, β-glucanase, and side enzymatic activities in both corn-SBM-based and wheat-barley-SBM-based diets had beneficial effects on feed conversion ratio in ISA Brown laying hens (45 to 54 wk of age), although egg production, egg weight, egg mass, and feed intake were not affected. However, using Babcock B-300 or Hy-Line W36 hens (25 to 40 wk of age), Scheideler et al. (2005) suggested that supplementation of a multi-enzymes (xylanase, protease, and α-amylase) to corn-SBM-based diets had no effect on feed intake, egg production, feed conversion ratio, egg weight, or egg mass. In the present study, dietary xylanase supplementation had no significant effect on ATTD of DM, N, or GE. These findings can partially explain the lack of effect of xylanase on production performance. Xylanase may improve nutrient digestibility via decreasing viscosity induced by soluble NSP (Mathlouthi et al., 2003; Mirzaie et al., 2012). Although digesta viscosity was not specifically determined in this study, it is possible that the lack of difference in nutrient digestibility may be due to that inclusion of 10% wheat in laying hen diets will not change the viscosity of intestinal digesta. In broilers, Liu and Kim (2016) suggested that xylanase improved gut health by increasing the lactic acid bacteria but reducing coliforms counts. Additionally, Engberg et al. (2004) and Nian et al. (2011) observed that dietary xylanase addition stimulated the growth of lactic acid bacteria. Similar to these findings, the results from this study showed no effect of xylanase supplementation of corn-SBM-wheat-based diets on Salmonella or coliforms counts, but on lactic acid bacteria counts. The possible explanation for the increased lactic acid bacteria counts may be that xylanase hydrolysis of arabinoxylan into fragments of arabinoxylan-oligosaccharides acted as prebiotics and stimulated lactic acid bacteria populations (Patterson and Burkholder, 2003; Bedford and Cowieson, 2012; Divani et al., 2017). In the present study, dietary supplementation with xylanase had no effect on eggshell strength, shell color, or yolk color. However, eggshell thickness was linearly increased in wk 3, 6, 9, and 12. Additionally, Haugh unit and albumen height were improved in wk 12. Cufadar et al. (2010) found that xylanase addition to corn- or wheat-SBM-based diets had no significant effect on yolk index, albumen index, Haugh unit, or yolk color in White Leghorn LSL laying hens between 52 and 64 wk of age. Pirgozliev et al. (2010) noted that inclusion of xylanase (0, 400, 800, 1200, and 1600 U/kg, respectively) in wheat-SBM-rye-based diet linearly increased yolk color, but shell color, albumen height, Haugh unit, and shell thickness were not affected in Lohmann Brown laying hens between 28 and 32 wk of age. Scheideler et al. (2005) observed that enzyme (xylanase, protease, and α-amylase) supplementation had no effect on Haugh unit or percentages of egg albumen, yolk, and shell, whereas yolk lightness was reduced in laying hens fed corn-SBM-based diets. Silversides et al. (2006) indicated that xylanase increased albumen height in laying hens fed diets with adequate phosphorus but not in those fed phosphorus-reduced diets. In agreement with our results, Mirzaie et al. (2012) observed that xylanase increased shell thickness in laying hens fed corn-SBM-wheat-based diets. The effectiveness of xylanase in improving eggshell thickness may be associated with the utilization of minerals. It is conceivable that the in situ production of arabinoxylan-oligosaccharides from hydrolysis of arabinoxylan results in the changes in intestinal pH and microbiota and therefore improves solubility and absorption of calcium (Damen et al., 2012; Li et al., 2017; Wang et al., 2017). The reason for the increased Haugh unit and albumen height is difficult to provide. Further experiments are required to explain the exact mechanism by which xylanase supplementation affects egg quality. In conclusion, the results of this study suggest that xylanase supplementation in corn-SBM-wheat-based diets could shift microbiota by increasing excreta lactic acid bacteria and improve egg quality indicated as increased eggshell thickness, Haugh unit and albumen height. 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This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Poultry Science Oxford University Press

Performance, egg quality, nutrient digestibility, and excreta microbiota shedding in laying hens fed corn-soybean-meal-wheat-based diets supplemented with xylanase

Poultry Science , Volume Advance Article (6) – Mar 1, 2018

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Oxford University Press
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© 2018 Poultry Science Association Inc.
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0032-5791
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Abstract

ABSTRACT The aim of this study was to evaluate the effects of dietary levels of xylanase on production performance, egg quality, nutrient digestibility, and excreta microbiota shedding of laying hens in a 12-week trial. Two-hundred-forty Hy-Line brown laying hens (44 wk old) were distributed according to a randomized block experimental design into one of 4 dietary treatments with 10 replicates of 6 birds each. The 4 dietary treatments were corn-soybean-meal-wheat-based diets supplemented with 0, 225, 450, or 900 U/kg xylanase. Daily feed intake, egg production, egg weight, egg mass, feed conversion ratio, and damaged egg rate showed no significant response to increasing xylanase supplementation during any phase (P > 0.05). No significant responses were observed for apparent total tract digestibility of dry matter, nitrogen, or gross energy (P > 0.05). A significant linear increase to increasing xylanase supplementation was seen for lactic acid bacteria numbers, although coliforms and Salmonella counts were not affected. Increasing the dietary xylanase resulted in a significant linear increase in eggshell thickness in wk 3, 6, 9, and 12 (P < 0.05). In addition, a significant linear increase occurred for Haugh unit and albumen height in wk 12 (P < 0.05). In summary, the inclusion of xylanase in corn-soybean-meal-wheat-based diets increased eggshell thickness, Haugh unit, albumen height, and excreta lactic acid bacteria count but had no effect on production performance or nutrient digestibility. INTRODUCTION Corn and wheat are dominant energy sources used in poultry diets worldwide because of their high energy content (Cufadar et al., 2010; Gatrell et al., 2014). Soybean meal (SBM) is the main protein ingredient for poultry diets (Laudadio and Tufarelli, 2011). However, the presence of non-starch polysaccharides (NSP) in wheat, corn, and SBM may negatively affect nutrient utilization and performance of poultry (Mathlouthi et al., 2003; Yegani and Korver, 2008; Kiarie et al., 2014; Jahanian and Golshadi, 2015). Previous studies demonstrated that around 5.2% arabinoxylan is present in corn, 8.1% arabinoxylan is present in wheat, and 3.3% arabinoxylan is present in SBM (Choct, 1997; Knudsen, 1997). Recently, the use of dietary enzymes in commercial laying hen diets has become a common practice (Slominski, 2011; Shastak et al., 2015; Erdaw et al., 2016; Gadde et al., 2017). Exogenous xylanases may improve intestinal microbial balance, nutrient digestibility, and performance in high soluble NSP (wheat-based) diets (Mathlouthi et al., 2002; Silversides et al., 2006; Mirzaie et al., 2012; Swiatkiewicz et al., 2016). However, there is increasing evidence suggesting that xylanase supplementation can improve the nutritional value of corn-SBM-based diets. Mathlouthi et al. (2003) suggested that multi-enzymes (xylanase and β-glucanase) exhibited beneficial effects on feed conversion ratio of hens fed not only a wheat-barley-based diet but also a maize-SBM-based diet. Bobeck et al. (2014) observed that dietary supplementation with xylanase enhanced egg mass, egg production, and feed efficiency in laying hens fed corn-SBM-dried distillers’ grains with solubles-based diets. Additionally, in laying quails, Bayram et al. (2008) found that inclusion of xylanase in corn-SBM-based diets improved feed conversion ratio. We hypothesized that the xylanase addition in a corn-wheat-SBM-based diet would improve nutrient digestibility and production performance in laying hens. Therefore, the current experiment was designed to study the effects of xylanase supplementation on production performance, egg quality, nutrient digestibility, and excreta microbiota shedding in laying hens fed a corn-wheat-SBM-based diet. MATERIALS AND METHODS The experimental protocols used in the study were approved by the Animal Care and Use Committee of Dankook University. Xylanase Source The xylanase used in this study was Nutrase Xyla (Nutrex Nv, Lille, Belgium), derived from fermentation by Bacillus subtilis. It is a specific endo-1, 4-β-xylanase (IUB: EC 3.2.1.8; 9,000 U/g) with an optimal activity at neutral pH. Xylanase activity was assayed using Xylazyme AX tablets (Megazyme International Ltd., Bray, Ireland). Experimental Birds and Design A total of 240 Hy-Line brown laying hens (44 wk of age) was randomly assigned to one of 4 treatments with 10 replications and 6 hens per replication (one hen/cage) in a 12-week feeding experiment. The 4 dietary treatments were corn-SBM-wheat-based diets supplemented with 0, 225, 450, or 900 U/kg xylanase. The composition of the basal diet is shown in Table 1 and was formulated according to the recommendations provided in NRC (1994). The hens were housed in a windowless and environmentally controlled room that was maintained at 23°C. Sixteen h (0500 to 2100 h) of artificial lighting were provided daily. All hens were housed individually in cages (38 cm width × 50 cm length × 40 cm height). Feed and water were provided for ad libitum consumption, and all diets were presented in mash form. Table 1. Composition and nutrient content of basal diet for laying hens (as-fed basis). Item Weeks 1 to 12 Ingredients, %  Corn 50.40  Soybean meal 18.70  Wheat 10.00  Corn gluten meal 2.00  Wheat bran 5.00  Animal fat 4.40  Limestone 7.50  Dicalcium phosphate 1.40  Salt 0.30  DL- Methionine 0.10  Vitamin premix1 0.10  Trace mineral premix2 0.10 Calculated nutrient content, %  Metabolizable energy, kcal/kg 2904  Crude protein 15.02  Calcium 3.25  Available phosphorus 0.38  Digestible lysine 0.66  Digestible methionine + cysteine 0.56  Digestible methionine 0.38  Digestible threonine 0.44  Digestible tryptophan 0.16 Analyzed nutrient content, %  Crude protein 15.09  Lysine 0.75  Calcium 3.22  Total phosphorus 0.58 Item Weeks 1 to 12 Ingredients, %  Corn 50.40  Soybean meal 18.70  Wheat 10.00  Corn gluten meal 2.00  Wheat bran 5.00  Animal fat 4.40  Limestone 7.50  Dicalcium phosphate 1.40  Salt 0.30  DL- Methionine 0.10  Vitamin premix1 0.10  Trace mineral premix2 0.10 Calculated nutrient content, %  Metabolizable energy, kcal/kg 2904  Crude protein 15.02  Calcium 3.25  Available phosphorus 0.38  Digestible lysine 0.66  Digestible methionine + cysteine 0.56  Digestible methionine 0.38  Digestible threonine 0.44  Digestible tryptophan 0.16 Analyzed nutrient content, %  Crude protein 15.09  Lysine 0.75  Calcium 3.22  Total phosphorus 0.58 1Provided per kilogram of diet: 12,500 IU vitamin A; 2,500 IU vitamin D3; 20 mg vitamin E; 2 mg vitamin K3; 1 mg vitamin B1; 5 mg vitamin B2; 1 mg vitamin B6; 15 μg vitamin B12; 1 mg folic acid; 35 mg niacin; 10 mg Ca-pantothenate and 50 μg biotin. 2Provided per kilogram of diet: 8 mg Mn (as MnO2); 60 mg Zn (as ZnSO4); 5 mg Cu (as CuSO4·5H2O); 40 mg Fe (as FeSO4·7H2O); 0.3 mg Co (as CoSO4·5H2O); 1.5 mg I (as KI) and 0.15 mg Se (as Na2SeO3·5H2O). View Large Table 1. Composition and nutrient content of basal diet for laying hens (as-fed basis). Item Weeks 1 to 12 Ingredients, %  Corn 50.40  Soybean meal 18.70  Wheat 10.00  Corn gluten meal 2.00  Wheat bran 5.00  Animal fat 4.40  Limestone 7.50  Dicalcium phosphate 1.40  Salt 0.30  DL- Methionine 0.10  Vitamin premix1 0.10  Trace mineral premix2 0.10 Calculated nutrient content, %  Metabolizable energy, kcal/kg 2904  Crude protein 15.02  Calcium 3.25  Available phosphorus 0.38  Digestible lysine 0.66  Digestible methionine + cysteine 0.56  Digestible methionine 0.38  Digestible threonine 0.44  Digestible tryptophan 0.16 Analyzed nutrient content, %  Crude protein 15.09  Lysine 0.75  Calcium 3.22  Total phosphorus 0.58 Item Weeks 1 to 12 Ingredients, %  Corn 50.40  Soybean meal 18.70  Wheat 10.00  Corn gluten meal 2.00  Wheat bran 5.00  Animal fat 4.40  Limestone 7.50  Dicalcium phosphate 1.40  Salt 0.30  DL- Methionine 0.10  Vitamin premix1 0.10  Trace mineral premix2 0.10 Calculated nutrient content, %  Metabolizable energy, kcal/kg 2904  Crude protein 15.02  Calcium 3.25  Available phosphorus 0.38  Digestible lysine 0.66  Digestible methionine + cysteine 0.56  Digestible methionine 0.38  Digestible threonine 0.44  Digestible tryptophan 0.16 Analyzed nutrient content, %  Crude protein 15.09  Lysine 0.75  Calcium 3.22  Total phosphorus 0.58 1Provided per kilogram of diet: 12,500 IU vitamin A; 2,500 IU vitamin D3; 20 mg vitamin E; 2 mg vitamin K3; 1 mg vitamin B1; 5 mg vitamin B2; 1 mg vitamin B6; 15 μg vitamin B12; 1 mg folic acid; 35 mg niacin; 10 mg Ca-pantothenate and 50 μg biotin. 2Provided per kilogram of diet: 8 mg Mn (as MnO2); 60 mg Zn (as ZnSO4); 5 mg Cu (as CuSO4·5H2O); 40 mg Fe (as FeSO4·7H2O); 0.3 mg Co (as CoSO4·5H2O); 1.5 mg I (as KI) and 0.15 mg Se (as Na2SeO3·5H2O). View Large Production Performance The number and weight of eggs laid were recorded daily, and feed intake was recorded weekly on a replication basis. Feed conversion ratio was calculated as gram of total feed intake per hen/gram of total egg mass per hen. The egg production was expressed as an average hen-day production. Egg mass was calculated by multiplying egg weight by egg production. The collected eggs were classified as either normal or damaged for calculating the damaged egg ratio. The damaged eggs included broken eggs, cracked eggs, and shell-less eggs. Egg Quality Parameters At the beginning of the experiment, and then at 3-week intervals, a total of 30 eggs (3 eggs per replication) with the exception of damaged eggs was randomly collected at 1700 h from each treatment and used to determine the egg quality at 2000 h the same day. Eggshell breaking strength was evaluated using an eggshell force gauge model II (Robotmation Co., Ltd., Tokyo, Japan). A dial pipe gauge (Ozaki MFG. Co., Ltd., Tokyo, Japan) was employed for measurements of the eggshell thickness, which was determined on the basis of the average thickness of the rounded end, pointed end, and the middle of the egg, excluding the inner membrane. An eggshell color fan was used to visually determine the eggshell color (DSM, Basel, Switzerland). Yolk color, yolk height, and Haugh unit were evaluated using an egg multi-tester (Touhoku Rhythm Co. Ltd., Tokyo, Japan). The measurements regarding egg quality were analyzed by one observer who was blind to the treatment. Apparent Total Tract Digestibility At 11 wk of the experiment, chromium oxide (0.2%) was included in the experimental diets as an indigestible marker to determine the apparent total tract digestibility (ATTD) of dry matter (DM), nitrogen (N), and gross energy (GE). During the last 3 d of the experiment, fresh excreta samples from each replication were collected and stored at –20°C until subsequent analysis was conducted. Contaminations such as feathers and scales were removed from the excreta. For chemical analysis, excreta samples were oven-dried at 60°C for 72 h, after which diets and excreta samples were ground to pass through a 1.0-mm screen for analysis of DM (method 930.15) and N (method 984.13) using the AOAC (2007) procedures. Gross energy was determined by measuring the heat of combustion in the samples, using a bomb calorimeter (Parr 6100; Parr Instrument Co., Moline, IL). Chromium was analyzed via UV absorption spectrophotometry (UV-1201, Shimadzu Corp., Kyoto, Japan), according to the method described by Williams et al. (1962). The ATTD was then calculated using the following formula: \begin{eqnarray*} {\rm{ATTD}}\left( \% \right) &=& \left[ {1 - \{ \left( {{\rm{Ne}} \times {\rm{Cf}}} \right)/\left( {{\rm{Nf}} \times {\rm{Ce}}} \right)\} } \right] \times 100, \end{eqnarray*} Where: Ne = nutrient concentration in excreta (% DM), Nf = nutrient concentration in feed (% DM), Cf = chromium concentration in feed (% DM), and Ce = chromium concentration in excreta (% DM). Excreta Microbial Shedding At the end of the experiment, excreta samples were randomly collected from 10 layers (one layer per replication) from each treatment, and then placed on ice for transportation to the laboratory. One gram of the composite excreta sample from each replication was diluted with 9 mL of 1% peptone broth (Becton, Dickinson and Co., Rutherford, NJ) and then homogenized. Viable counts of bacteria in the excreta samples were then determined by plating serial 10-fold dilutions (in 10 g/L peptone solution) onto MacConkey agar plates (Difco Laboratories, Detroit, MI), lactobacilli medium III agar plates (Medium 638; DSMZ, Braunschweig, Germany), and Salmonella-Shigella agar plates to isolate coliforms, lactic acid bacteria, and Salmonella, respectively. The lactobacilli medium III agar plates were then incubated for 48 h at 37°C under anaerobic conditions. The MacConkey and Salmonella-Shigella agar plates were both incubated for 24 h at 37°C. The microbial colonies were counted immediately after removal from the incubator. The microbial populations were finally expressed as log10 colony-forming units per gram of excreta. Statistical Analyses All data were subjected to statistical analysis in a randomized complete block design using the General Linear Model procedure (SAS Institute, Cary, NC). Replication (n = 10) was used as the experimental unit. Orthogonal contrasts were used to examine the linear, quadratic, and cubic effects in response to increasing the dietary supplementation of xylanase. The results were presented as means and pooled standard error of the mean. Probability values less than 0.05 were considered significant. RESULTS Productive Performance and Egg Quality The effects of xylanase supplementation in corn-wheat-SBM-based diets on productive performance are presented in Table 2. Throughout the experiment, daily feed intake, egg production, egg weight, egg mass, feed conversion ratio, and damaged eggs rate were not affected by xylanase supplementation. No significant effects of xylanase supplementation were found for eggshell strength or shell color throughout the experiment (P > 0.05; Table 3). There was a significant linear increase (P < 0.05) in eggshell thickness in response to increasing xylanase supplementation in wk 3, 6, 9, and 12. Additionally, as xylanase supplementation increased, Haugh unit and albumen height increased (P < 0.05) linearly in wk 12. Table 2. Effects of xylanase supplementation on production performance in laying hens from 44 to 56 wk of age. Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Weeks 1 to 3  Daily feed intake, g/d/hen 108.71 106.29 106.86 106.14 0.91 0.091 0.355 0.302  Egg production, % 89.80 89.48 90.99 90.70 0.98 0.347 0.989 0.415  Egg weight, g 65.78 65.79 65.75 65.89 1.31 0.961 0.958 0.969  Egg mass, g/d/hen 59.06 58.84 59.81 59.76 1.25 0.588 0.950 0.694  FCR1, g feed/g egg 1.84 1.81 1.80 1.78 0.05 0.349 0.873 0.965  Damaged egg ratio, % 0.57 0.43 0.20 0.33 0.37 0.235 0.617 0.620 Weeks 4 to 6  Daily feed intake, g/d/hen 108.00 108.71 109.71 108.00 0.64 0.730 0.070 0.305  Egg production, % 89.41 89.34 89.83 90.03 0.94 0.581 0.885 0.844  Egg weight, g 65.21 65.69 65.95 66.13 1.37 0.628 0.912 0.984  Egg mass, g/d/hen 58.24 58.70 59.25 59.59 1.36 0.459 0.963 0.959  FCR1, g feed/g egg 1.86 1.86 1.85 1.82 0.05 0.554 0.743 0.861  Damaged egg ratio, % 0.33 0.20 0.23 0.00 0.26 0.499 0.287 0.742 Weeks 7 to 9  Daily feed intake, g/d/hen 109.71 108.86 108.43 109.71 0.79 0.904 0.185 0.717  Egg production, % 87.70 88.14 88.54 89.03 1.15 0.399 0.983 0.978  Egg weight, g 64.49 67.13 65.58 64.94 1.63 0.982 0.327 0.498  Egg mass, g/d/hen 56.58 57.17 58.09 57.82 1.74 0.733 0.420 0.570  FCR1, g feed/g egg 1.95 1.85 1.88 1.91 0.06 0.771 0.342 0.647  Damaged egg ratio, % 0.00 0.23 0.33 0.43 0.28 0.320 0.604 0.562 Weeks 9 to 12  Daily feed intake, g/d/hen 111.71 109.71 109.43 109.29 1.03 0.113 0.376 0.736  Egg production, % 86.24 86.81 87.34 87.82 1.34 0.390 0.970 0.997  Egg weight, g 64.85 65.03 65.15 65.45 1.30 0.746 0.965 0.967  Egg mass, g/d/hen 55.99 56.44 56.87 57.49 1.48 0.465 0.954 0.974  FCR1, g feed/g egg 2.01 1.95 1.93 1.91 0.06 0.253 0.743 0.866  Damaged egg ratio, % 0.37 0.33 0.33 0.10 0.31 0.460 0.686 0.383 Weeks 1 to 12  Daily feed intake, g/d/hen 109.54 108.39 108.61 108.29 0.49 0.118 0.408 0.394  Egg production, % 88.29 88.44 89.17 89.39 0.68 0.194 0.964 0.727  Egg weight, g 65.60 65.61 65.90 65.08 0.68 0.683 0.551 0.648  Egg mass, g/d/hen 57.47 58.29 58.51 58.66 0.75 0.268 0.663 0.872  FCR1, g feed/g egg 1.91 1.86 1.86 1.85 0.03 0.165 0.495 0.692  Damaged egg ratio, % 0.32 0.30 0.28 0.22 0.09 0.421 0.731 0.989 Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Weeks 1 to 3  Daily feed intake, g/d/hen 108.71 106.29 106.86 106.14 0.91 0.091 0.355 0.302  Egg production, % 89.80 89.48 90.99 90.70 0.98 0.347 0.989 0.415  Egg weight, g 65.78 65.79 65.75 65.89 1.31 0.961 0.958 0.969  Egg mass, g/d/hen 59.06 58.84 59.81 59.76 1.25 0.588 0.950 0.694  FCR1, g feed/g egg 1.84 1.81 1.80 1.78 0.05 0.349 0.873 0.965  Damaged egg ratio, % 0.57 0.43 0.20 0.33 0.37 0.235 0.617 0.620 Weeks 4 to 6  Daily feed intake, g/d/hen 108.00 108.71 109.71 108.00 0.64 0.730 0.070 0.305  Egg production, % 89.41 89.34 89.83 90.03 0.94 0.581 0.885 0.844  Egg weight, g 65.21 65.69 65.95 66.13 1.37 0.628 0.912 0.984  Egg mass, g/d/hen 58.24 58.70 59.25 59.59 1.36 0.459 0.963 0.959  FCR1, g feed/g egg 1.86 1.86 1.85 1.82 0.05 0.554 0.743 0.861  Damaged egg ratio, % 0.33 0.20 0.23 0.00 0.26 0.499 0.287 0.742 Weeks 7 to 9  Daily feed intake, g/d/hen 109.71 108.86 108.43 109.71 0.79 0.904 0.185 0.717  Egg production, % 87.70 88.14 88.54 89.03 1.15 0.399 0.983 0.978  Egg weight, g 64.49 67.13 65.58 64.94 1.63 0.982 0.327 0.498  Egg mass, g/d/hen 56.58 57.17 58.09 57.82 1.74 0.733 0.420 0.570  FCR1, g feed/g egg 1.95 1.85 1.88 1.91 0.06 0.771 0.342 0.647  Damaged egg ratio, % 0.00 0.23 0.33 0.43 0.28 0.320 0.604 0.562 Weeks 9 to 12  Daily feed intake, g/d/hen 111.71 109.71 109.43 109.29 1.03 0.113 0.376 0.736  Egg production, % 86.24 86.81 87.34 87.82 1.34 0.390 0.970 0.997  Egg weight, g 64.85 65.03 65.15 65.45 1.30 0.746 0.965 0.967  Egg mass, g/d/hen 55.99 56.44 56.87 57.49 1.48 0.465 0.954 0.974  FCR1, g feed/g egg 2.01 1.95 1.93 1.91 0.06 0.253 0.743 0.866  Damaged egg ratio, % 0.37 0.33 0.33 0.10 0.31 0.460 0.686 0.383 Weeks 1 to 12  Daily feed intake, g/d/hen 109.54 108.39 108.61 108.29 0.49 0.118 0.408 0.394  Egg production, % 88.29 88.44 89.17 89.39 0.68 0.194 0.964 0.727  Egg weight, g 65.60 65.61 65.90 65.08 0.68 0.683 0.551 0.648  Egg mass, g/d/hen 57.47 58.29 58.51 58.66 0.75 0.268 0.663 0.872  FCR1, g feed/g egg 1.91 1.86 1.86 1.85 0.03 0.165 0.495 0.692  Damaged egg ratio, % 0.32 0.30 0.28 0.22 0.09 0.421 0.731 0.989 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 2. Effects of xylanase supplementation on production performance in laying hens from 44 to 56 wk of age. Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Weeks 1 to 3  Daily feed intake, g/d/hen 108.71 106.29 106.86 106.14 0.91 0.091 0.355 0.302  Egg production, % 89.80 89.48 90.99 90.70 0.98 0.347 0.989 0.415  Egg weight, g 65.78 65.79 65.75 65.89 1.31 0.961 0.958 0.969  Egg mass, g/d/hen 59.06 58.84 59.81 59.76 1.25 0.588 0.950 0.694  FCR1, g feed/g egg 1.84 1.81 1.80 1.78 0.05 0.349 0.873 0.965  Damaged egg ratio, % 0.57 0.43 0.20 0.33 0.37 0.235 0.617 0.620 Weeks 4 to 6  Daily feed intake, g/d/hen 108.00 108.71 109.71 108.00 0.64 0.730 0.070 0.305  Egg production, % 89.41 89.34 89.83 90.03 0.94 0.581 0.885 0.844  Egg weight, g 65.21 65.69 65.95 66.13 1.37 0.628 0.912 0.984  Egg mass, g/d/hen 58.24 58.70 59.25 59.59 1.36 0.459 0.963 0.959  FCR1, g feed/g egg 1.86 1.86 1.85 1.82 0.05 0.554 0.743 0.861  Damaged egg ratio, % 0.33 0.20 0.23 0.00 0.26 0.499 0.287 0.742 Weeks 7 to 9  Daily feed intake, g/d/hen 109.71 108.86 108.43 109.71 0.79 0.904 0.185 0.717  Egg production, % 87.70 88.14 88.54 89.03 1.15 0.399 0.983 0.978  Egg weight, g 64.49 67.13 65.58 64.94 1.63 0.982 0.327 0.498  Egg mass, g/d/hen 56.58 57.17 58.09 57.82 1.74 0.733 0.420 0.570  FCR1, g feed/g egg 1.95 1.85 1.88 1.91 0.06 0.771 0.342 0.647  Damaged egg ratio, % 0.00 0.23 0.33 0.43 0.28 0.320 0.604 0.562 Weeks 9 to 12  Daily feed intake, g/d/hen 111.71 109.71 109.43 109.29 1.03 0.113 0.376 0.736  Egg production, % 86.24 86.81 87.34 87.82 1.34 0.390 0.970 0.997  Egg weight, g 64.85 65.03 65.15 65.45 1.30 0.746 0.965 0.967  Egg mass, g/d/hen 55.99 56.44 56.87 57.49 1.48 0.465 0.954 0.974  FCR1, g feed/g egg 2.01 1.95 1.93 1.91 0.06 0.253 0.743 0.866  Damaged egg ratio, % 0.37 0.33 0.33 0.10 0.31 0.460 0.686 0.383 Weeks 1 to 12  Daily feed intake, g/d/hen 109.54 108.39 108.61 108.29 0.49 0.118 0.408 0.394  Egg production, % 88.29 88.44 89.17 89.39 0.68 0.194 0.964 0.727  Egg weight, g 65.60 65.61 65.90 65.08 0.68 0.683 0.551 0.648  Egg mass, g/d/hen 57.47 58.29 58.51 58.66 0.75 0.268 0.663 0.872  FCR1, g feed/g egg 1.91 1.86 1.86 1.85 0.03 0.165 0.495 0.692  Damaged egg ratio, % 0.32 0.30 0.28 0.22 0.09 0.421 0.731 0.989 Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Weeks 1 to 3  Daily feed intake, g/d/hen 108.71 106.29 106.86 106.14 0.91 0.091 0.355 0.302  Egg production, % 89.80 89.48 90.99 90.70 0.98 0.347 0.989 0.415  Egg weight, g 65.78 65.79 65.75 65.89 1.31 0.961 0.958 0.969  Egg mass, g/d/hen 59.06 58.84 59.81 59.76 1.25 0.588 0.950 0.694  FCR1, g feed/g egg 1.84 1.81 1.80 1.78 0.05 0.349 0.873 0.965  Damaged egg ratio, % 0.57 0.43 0.20 0.33 0.37 0.235 0.617 0.620 Weeks 4 to 6  Daily feed intake, g/d/hen 108.00 108.71 109.71 108.00 0.64 0.730 0.070 0.305  Egg production, % 89.41 89.34 89.83 90.03 0.94 0.581 0.885 0.844  Egg weight, g 65.21 65.69 65.95 66.13 1.37 0.628 0.912 0.984  Egg mass, g/d/hen 58.24 58.70 59.25 59.59 1.36 0.459 0.963 0.959  FCR1, g feed/g egg 1.86 1.86 1.85 1.82 0.05 0.554 0.743 0.861  Damaged egg ratio, % 0.33 0.20 0.23 0.00 0.26 0.499 0.287 0.742 Weeks 7 to 9  Daily feed intake, g/d/hen 109.71 108.86 108.43 109.71 0.79 0.904 0.185 0.717  Egg production, % 87.70 88.14 88.54 89.03 1.15 0.399 0.983 0.978  Egg weight, g 64.49 67.13 65.58 64.94 1.63 0.982 0.327 0.498  Egg mass, g/d/hen 56.58 57.17 58.09 57.82 1.74 0.733 0.420 0.570  FCR1, g feed/g egg 1.95 1.85 1.88 1.91 0.06 0.771 0.342 0.647  Damaged egg ratio, % 0.00 0.23 0.33 0.43 0.28 0.320 0.604 0.562 Weeks 9 to 12  Daily feed intake, g/d/hen 111.71 109.71 109.43 109.29 1.03 0.113 0.376 0.736  Egg production, % 86.24 86.81 87.34 87.82 1.34 0.390 0.970 0.997  Egg weight, g 64.85 65.03 65.15 65.45 1.30 0.746 0.965 0.967  Egg mass, g/d/hen 55.99 56.44 56.87 57.49 1.48 0.465 0.954 0.974  FCR1, g feed/g egg 2.01 1.95 1.93 1.91 0.06 0.253 0.743 0.866  Damaged egg ratio, % 0.37 0.33 0.33 0.10 0.31 0.460 0.686 0.383 Weeks 1 to 12  Daily feed intake, g/d/hen 109.54 108.39 108.61 108.29 0.49 0.118 0.408 0.394  Egg production, % 88.29 88.44 89.17 89.39 0.68 0.194 0.964 0.727  Egg weight, g 65.60 65.61 65.90 65.08 0.68 0.683 0.551 0.648  Egg mass, g/d/hen 57.47 58.29 58.51 58.66 0.75 0.268 0.663 0.872  FCR1, g feed/g egg 1.91 1.86 1.86 1.85 0.03 0.165 0.495 0.692  Damaged egg ratio, % 0.32 0.30 0.28 0.22 0.09 0.421 0.731 0.989 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 3. Effects of xylanase supplementation on egg quality in laying hens from 44 to 56 wk of age. Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Initial  Shell color 10.71 10.52 10.89 10.74 0.21 0.490 0.722 0.127  Eggshell strength, kg/cm2 3.88 3.86 3.89 3.88 0.03 0.169 0.676 0.433  Haugh Unit 90.61 91.03 90.44 90.73 1.11 0.993 0.431 0.952  Albumen height, mm 8.51 8.62 8.50 8.63 0.21 0.966 0.434 0.989  Yolk color 7.89 8.03 7.78 7.81 0.25 0.560 0.852 0.617  Eggshell thickness, 10−2 mm 46.60 46.52 46.67 46.71 0.52 0.479 0.335 0.904 Week 3  Shell color 10.22 10.13 10.12 10.45 0.40 0.548 0.573 0.892  Eggshell strength, kg/cm2 3.83 3.85 3.87 3.88 0.02 0.068 0.841 0.931  Haugh Unit 89.01 89.67 90.34 90.51 1.01 0.232 0.782 0.996  Albumen height, mm 8.23 8.31 8.44 8.52 0.19 0.183 0.880 0.987  Yolk color 8.3 8.29 8.31 8.10 0.34 0.731 0.719 0.909  Eggshell thickness, 10−2 mm 45.02 45.67 45.91 46.54 0.50 0.037 0.845 0.580 Week 6  Shell color 10.02 10.74 9.78 10.14 0.34 0.650 0.530 0.075  Eggshell strength, kg/cm2 3.83 3.85 3.86 3.88 0.02 0.065 0.903 0.925  Haugh Unit 89.84 90.77 91.19 91.81 0.98 0.143 0.872 0.868  Albumen height, mm 8.27 8.51 8.59 8.72 0.18 0.113 0.896 0.854  Yolk color 8.14 8.31 8.33 7.92 0.35 0.660 0.326 0.986  Eggshell thickness, 10−2 mm 44.82 45.67 46.04 46.81 0.59 0.021 0.955 0.631 Week 9  Shell color 10.67 10.21 10.33 10.44 0.36 0.617 0.403 0.708  Eggshell strength, kg/cm2 3.83 3.84 3.85 3.86 0.02 0.261 0.942 0.970  Haugh Unit 90.32 90.78 91.22 91.83 0.78 0.175 0.988 0.970  Albumen height, mm 8.41 8.45 8.62 8.67 0.14 0.100 0.996 0.905  Yolk color 8.24 8.21 8.20 8.33 0.32 0.875 0.880 0.982  Eggshell thickness, 10−2 mm 44.61 45.56 45.63 46.33 0.43 0.012 0.803 0.494 Week 12  Shell color 11.11 10.67 11.13 10.71 0.33 0.633 0.945 0.271  Eggshell strength, kg/cm2 3.86 3.88 3.89 3.92 0.03 0.118 0.862 0.950  Haugh Unit 89.92 91.79 92.70 93.22 0.66 0.001 0.406 0.894  Albumen height, mm 8.43 8.70 8.89 9.04 0.11 <0.001 0.383 0.975  Yolk color 8.30 8.11 8.31 8.34 0.28 0.941 0.868 0.631  Eggshell thickness,10−2 mm 45.27 45.77 46.07 46.43 0.36 0.014 0.854 0.874 Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Initial  Shell color 10.71 10.52 10.89 10.74 0.21 0.490 0.722 0.127  Eggshell strength, kg/cm2 3.88 3.86 3.89 3.88 0.03 0.169 0.676 0.433  Haugh Unit 90.61 91.03 90.44 90.73 1.11 0.993 0.431 0.952  Albumen height, mm 8.51 8.62 8.50 8.63 0.21 0.966 0.434 0.989  Yolk color 7.89 8.03 7.78 7.81 0.25 0.560 0.852 0.617  Eggshell thickness, 10−2 mm 46.60 46.52 46.67 46.71 0.52 0.479 0.335 0.904 Week 3  Shell color 10.22 10.13 10.12 10.45 0.40 0.548 0.573 0.892  Eggshell strength, kg/cm2 3.83 3.85 3.87 3.88 0.02 0.068 0.841 0.931  Haugh Unit 89.01 89.67 90.34 90.51 1.01 0.232 0.782 0.996  Albumen height, mm 8.23 8.31 8.44 8.52 0.19 0.183 0.880 0.987  Yolk color 8.3 8.29 8.31 8.10 0.34 0.731 0.719 0.909  Eggshell thickness, 10−2 mm 45.02 45.67 45.91 46.54 0.50 0.037 0.845 0.580 Week 6  Shell color 10.02 10.74 9.78 10.14 0.34 0.650 0.530 0.075  Eggshell strength, kg/cm2 3.83 3.85 3.86 3.88 0.02 0.065 0.903 0.925  Haugh Unit 89.84 90.77 91.19 91.81 0.98 0.143 0.872 0.868  Albumen height, mm 8.27 8.51 8.59 8.72 0.18 0.113 0.896 0.854  Yolk color 8.14 8.31 8.33 7.92 0.35 0.660 0.326 0.986  Eggshell thickness, 10−2 mm 44.82 45.67 46.04 46.81 0.59 0.021 0.955 0.631 Week 9  Shell color 10.67 10.21 10.33 10.44 0.36 0.617 0.403 0.708  Eggshell strength, kg/cm2 3.83 3.84 3.85 3.86 0.02 0.261 0.942 0.970  Haugh Unit 90.32 90.78 91.22 91.83 0.78 0.175 0.988 0.970  Albumen height, mm 8.41 8.45 8.62 8.67 0.14 0.100 0.996 0.905  Yolk color 8.24 8.21 8.20 8.33 0.32 0.875 0.880 0.982  Eggshell thickness, 10−2 mm 44.61 45.56 45.63 46.33 0.43 0.012 0.803 0.494 Week 12  Shell color 11.11 10.67 11.13 10.71 0.33 0.633 0.945 0.271  Eggshell strength, kg/cm2 3.86 3.88 3.89 3.92 0.03 0.118 0.862 0.950  Haugh Unit 89.92 91.79 92.70 93.22 0.66 0.001 0.406 0.894  Albumen height, mm 8.43 8.70 8.89 9.04 0.11 <0.001 0.383 0.975  Yolk color 8.30 8.11 8.31 8.34 0.28 0.941 0.868 0.631  Eggshell thickness,10−2 mm 45.27 45.77 46.07 46.43 0.36 0.014 0.854 0.874 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 3. Effects of xylanase supplementation on egg quality in laying hens from 44 to 56 wk of age. Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Initial  Shell color 10.71 10.52 10.89 10.74 0.21 0.490 0.722 0.127  Eggshell strength, kg/cm2 3.88 3.86 3.89 3.88 0.03 0.169 0.676 0.433  Haugh Unit 90.61 91.03 90.44 90.73 1.11 0.993 0.431 0.952  Albumen height, mm 8.51 8.62 8.50 8.63 0.21 0.966 0.434 0.989  Yolk color 7.89 8.03 7.78 7.81 0.25 0.560 0.852 0.617  Eggshell thickness, 10−2 mm 46.60 46.52 46.67 46.71 0.52 0.479 0.335 0.904 Week 3  Shell color 10.22 10.13 10.12 10.45 0.40 0.548 0.573 0.892  Eggshell strength, kg/cm2 3.83 3.85 3.87 3.88 0.02 0.068 0.841 0.931  Haugh Unit 89.01 89.67 90.34 90.51 1.01 0.232 0.782 0.996  Albumen height, mm 8.23 8.31 8.44 8.52 0.19 0.183 0.880 0.987  Yolk color 8.3 8.29 8.31 8.10 0.34 0.731 0.719 0.909  Eggshell thickness, 10−2 mm 45.02 45.67 45.91 46.54 0.50 0.037 0.845 0.580 Week 6  Shell color 10.02 10.74 9.78 10.14 0.34 0.650 0.530 0.075  Eggshell strength, kg/cm2 3.83 3.85 3.86 3.88 0.02 0.065 0.903 0.925  Haugh Unit 89.84 90.77 91.19 91.81 0.98 0.143 0.872 0.868  Albumen height, mm 8.27 8.51 8.59 8.72 0.18 0.113 0.896 0.854  Yolk color 8.14 8.31 8.33 7.92 0.35 0.660 0.326 0.986  Eggshell thickness, 10−2 mm 44.82 45.67 46.04 46.81 0.59 0.021 0.955 0.631 Week 9  Shell color 10.67 10.21 10.33 10.44 0.36 0.617 0.403 0.708  Eggshell strength, kg/cm2 3.83 3.84 3.85 3.86 0.02 0.261 0.942 0.970  Haugh Unit 90.32 90.78 91.22 91.83 0.78 0.175 0.988 0.970  Albumen height, mm 8.41 8.45 8.62 8.67 0.14 0.100 0.996 0.905  Yolk color 8.24 8.21 8.20 8.33 0.32 0.875 0.880 0.982  Eggshell thickness, 10−2 mm 44.61 45.56 45.63 46.33 0.43 0.012 0.803 0.494 Week 12  Shell color 11.11 10.67 11.13 10.71 0.33 0.633 0.945 0.271  Eggshell strength, kg/cm2 3.86 3.88 3.89 3.92 0.03 0.118 0.862 0.950  Haugh Unit 89.92 91.79 92.70 93.22 0.66 0.001 0.406 0.894  Albumen height, mm 8.43 8.70 8.89 9.04 0.11 <0.001 0.383 0.975  Yolk color 8.30 8.11 8.31 8.34 0.28 0.941 0.868 0.631  Eggshell thickness,10−2 mm 45.27 45.77 46.07 46.43 0.36 0.014 0.854 0.874 Xylanase supplementation (U/kg) P-value Item 0 225 450 900 SEM1 L1 Q1 C1 Initial  Shell color 10.71 10.52 10.89 10.74 0.21 0.490 0.722 0.127  Eggshell strength, kg/cm2 3.88 3.86 3.89 3.88 0.03 0.169 0.676 0.433  Haugh Unit 90.61 91.03 90.44 90.73 1.11 0.993 0.431 0.952  Albumen height, mm 8.51 8.62 8.50 8.63 0.21 0.966 0.434 0.989  Yolk color 7.89 8.03 7.78 7.81 0.25 0.560 0.852 0.617  Eggshell thickness, 10−2 mm 46.60 46.52 46.67 46.71 0.52 0.479 0.335 0.904 Week 3  Shell color 10.22 10.13 10.12 10.45 0.40 0.548 0.573 0.892  Eggshell strength, kg/cm2 3.83 3.85 3.87 3.88 0.02 0.068 0.841 0.931  Haugh Unit 89.01 89.67 90.34 90.51 1.01 0.232 0.782 0.996  Albumen height, mm 8.23 8.31 8.44 8.52 0.19 0.183 0.880 0.987  Yolk color 8.3 8.29 8.31 8.10 0.34 0.731 0.719 0.909  Eggshell thickness, 10−2 mm 45.02 45.67 45.91 46.54 0.50 0.037 0.845 0.580 Week 6  Shell color 10.02 10.74 9.78 10.14 0.34 0.650 0.530 0.075  Eggshell strength, kg/cm2 3.83 3.85 3.86 3.88 0.02 0.065 0.903 0.925  Haugh Unit 89.84 90.77 91.19 91.81 0.98 0.143 0.872 0.868  Albumen height, mm 8.27 8.51 8.59 8.72 0.18 0.113 0.896 0.854  Yolk color 8.14 8.31 8.33 7.92 0.35 0.660 0.326 0.986  Eggshell thickness, 10−2 mm 44.82 45.67 46.04 46.81 0.59 0.021 0.955 0.631 Week 9  Shell color 10.67 10.21 10.33 10.44 0.36 0.617 0.403 0.708  Eggshell strength, kg/cm2 3.83 3.84 3.85 3.86 0.02 0.261 0.942 0.970  Haugh Unit 90.32 90.78 91.22 91.83 0.78 0.175 0.988 0.970  Albumen height, mm 8.41 8.45 8.62 8.67 0.14 0.100 0.996 0.905  Yolk color 8.24 8.21 8.20 8.33 0.32 0.875 0.880 0.982  Eggshell thickness, 10−2 mm 44.61 45.56 45.63 46.33 0.43 0.012 0.803 0.494 Week 12  Shell color 11.11 10.67 11.13 10.71 0.33 0.633 0.945 0.271  Eggshell strength, kg/cm2 3.86 3.88 3.89 3.92 0.03 0.118 0.862 0.950  Haugh Unit 89.92 91.79 92.70 93.22 0.66 0.001 0.406 0.894  Albumen height, mm 8.43 8.70 8.89 9.04 0.11 <0.001 0.383 0.975  Yolk color 8.30 8.11 8.31 8.34 0.28 0.941 0.868 0.631  Eggshell thickness,10−2 mm 45.27 45.77 46.07 46.43 0.36 0.014 0.854 0.874 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Apparent Total Tract Digestibility and Excreta Microbiota Shedding There were no significant differences in ATTD of DM, N, or GE due to the dietary treatments (P > 0.05; Table 4). A significant linear increase (P < 0.05) due to increasing xylanase supplementation was observed for lactic acid bacteria counts, but coliforms and Salmonella numbers were not affected (Table 5). Table 4. Effects of 12-week xylanase supplementation on apparent total tract digestibility in laying hens. Xylanase supplementation (U/kg) P-value Items, % 0 225 450 900 SEM1 L1 Q1 C1 Dry matter 73.11 73.65 73.71 73.75 0.97 0.654 0.802 0.919 Nitrogen 64.45 63.93 64.11 64.70 1.21 0.856 0.631 0.952 Gross energy 75.71 75.78 75.78 75.81 0.80 0.935 0.974 0.977 Xylanase supplementation (U/kg) P-value Items, % 0 225 450 900 SEM1 L1 Q1 C1 Dry matter 73.11 73.65 73.71 73.75 0.97 0.654 0.802 0.919 Nitrogen 64.45 63.93 64.11 64.70 1.21 0.856 0.631 0.952 Gross energy 75.71 75.78 75.78 75.81 0.80 0.935 0.974 0.977 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 4. Effects of 12-week xylanase supplementation on apparent total tract digestibility in laying hens. Xylanase supplementation (U/kg) P-value Items, % 0 225 450 900 SEM1 L1 Q1 C1 Dry matter 73.11 73.65 73.71 73.75 0.97 0.654 0.802 0.919 Nitrogen 64.45 63.93 64.11 64.70 1.21 0.856 0.631 0.952 Gross energy 75.71 75.78 75.78 75.81 0.80 0.935 0.974 0.977 Xylanase supplementation (U/kg) P-value Items, % 0 225 450 900 SEM1 L1 Q1 C1 Dry matter 73.11 73.65 73.71 73.75 0.97 0.654 0.802 0.919 Nitrogen 64.45 63.93 64.11 64.70 1.21 0.856 0.631 0.952 Gross energy 75.71 75.78 75.78 75.81 0.80 0.935 0.974 0.977 1C, cubic; FCR, feed conversion ratio; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 5. Effects of 12-week xylanase supplementation on excreta microbial shedding in laying hens. Xylanase supplementation (U/kg) P-value Items, log10 cfu/g 0 225 450 900 SEM1 L1 Q1 C1 Lactic acid bacteria 7.58 7.64 7.69 7.74 0.03 0.003 0.906 0.847 Coliforms 5.90 5.88 5.87 5.84 0.04 0.315 0.952 0.871 Salmonella 2.52 2.48 2.40 2.37 0.07 0.135 0.931 0.763 Xylanase supplementation (U/kg) P-value Items, log10 cfu/g 0 225 450 900 SEM1 L1 Q1 C1 Lactic acid bacteria 7.58 7.64 7.69 7.74 0.03 0.003 0.906 0.847 Coliforms 5.90 5.88 5.87 5.84 0.04 0.315 0.952 0.871 Salmonella 2.52 2.48 2.40 2.37 0.07 0.135 0.931 0.763 1C, cubic; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large Table 5. Effects of 12-week xylanase supplementation on excreta microbial shedding in laying hens. Xylanase supplementation (U/kg) P-value Items, log10 cfu/g 0 225 450 900 SEM1 L1 Q1 C1 Lactic acid bacteria 7.58 7.64 7.69 7.74 0.03 0.003 0.906 0.847 Coliforms 5.90 5.88 5.87 5.84 0.04 0.315 0.952 0.871 Salmonella 2.52 2.48 2.40 2.37 0.07 0.135 0.931 0.763 Xylanase supplementation (U/kg) P-value Items, log10 cfu/g 0 225 450 900 SEM1 L1 Q1 C1 Lactic acid bacteria 7.58 7.64 7.69 7.74 0.03 0.003 0.906 0.847 Coliforms 5.90 5.88 5.87 5.84 0.04 0.315 0.952 0.871 Salmonella 2.52 2.48 2.40 2.37 0.07 0.135 0.931 0.763 1C, cubic; L, linear; Q, quadratic; SEM, pooled standard error of the mean. View Large DISCUSSION Studies have shown improvements in production performance when xylanase was included in laying hen diets; but the effects of xylanase on the performance of laying hens is conflicting. Senkoylu et al. (2009) reported that inclusion of xylanase in corn-SBM-whole-wheat-based diets improved feed conversion ratio and egg production in Bovans White layers from 53 to 63 wk of age. Bobeck et al. (2014) indicated that supplementation of xylanase to corn-SBM-dried distillers’ grain-based diets improved egg production, egg mass, and feed efficiency in Hy-Line W-36 laying hens from 22 to 44 wk of age. Cufadar et al. (2010) determined the effects of adding 3 levels of xylanase (0, 100, and 200 mg/kg, respectively) to 5 experimental diets with 5 corn: wheat ratios (100:0, 75:25, 50:50, 25:75, and 0:100, respectively) in White Leghorn LSL laying hens (52 to 64 wk of age). However, Cufadar et al. (2010) observed that xylanase supplementation had no effect on performance, including egg production, egg weight, feed intake, and feed conversion ratio. In our study, there was no effect on daily feed intake, egg production, egg weight, egg mass, feed conversion ratio, or cracked-egg rate when xylanase was supplemented in diets during any phase, suggesting that inclusion of xylanase in corn-SBM-wheat-based diets did not affect productive performance in laying hens. The conflicting findings between different studies may be due to differences in the age and strain of laying hens, the differences in the concentrations of xylanase, and the differences in compositions of diets. Additionally, supplementation of xylanase alone or in combination with different enzymes also may contribute to the inconsistent results concerning the performance of laying hens. Mathlouthi et al. (2003) found that inclusion of a multi-enzyme preparation containing xylanase, β-glucanase, and side enzymatic activities in both corn-SBM-based and wheat-barley-SBM-based diets had beneficial effects on feed conversion ratio in ISA Brown laying hens (45 to 54 wk of age), although egg production, egg weight, egg mass, and feed intake were not affected. However, using Babcock B-300 or Hy-Line W36 hens (25 to 40 wk of age), Scheideler et al. (2005) suggested that supplementation of a multi-enzymes (xylanase, protease, and α-amylase) to corn-SBM-based diets had no effect on feed intake, egg production, feed conversion ratio, egg weight, or egg mass. In the present study, dietary xylanase supplementation had no significant effect on ATTD of DM, N, or GE. These findings can partially explain the lack of effect of xylanase on production performance. Xylanase may improve nutrient digestibility via decreasing viscosity induced by soluble NSP (Mathlouthi et al., 2003; Mirzaie et al., 2012). Although digesta viscosity was not specifically determined in this study, it is possible that the lack of difference in nutrient digestibility may be due to that inclusion of 10% wheat in laying hen diets will not change the viscosity of intestinal digesta. In broilers, Liu and Kim (2016) suggested that xylanase improved gut health by increasing the lactic acid bacteria but reducing coliforms counts. Additionally, Engberg et al. (2004) and Nian et al. (2011) observed that dietary xylanase addition stimulated the growth of lactic acid bacteria. Similar to these findings, the results from this study showed no effect of xylanase supplementation of corn-SBM-wheat-based diets on Salmonella or coliforms counts, but on lactic acid bacteria counts. The possible explanation for the increased lactic acid bacteria counts may be that xylanase hydrolysis of arabinoxylan into fragments of arabinoxylan-oligosaccharides acted as prebiotics and stimulated lactic acid bacteria populations (Patterson and Burkholder, 2003; Bedford and Cowieson, 2012; Divani et al., 2017). In the present study, dietary supplementation with xylanase had no effect on eggshell strength, shell color, or yolk color. However, eggshell thickness was linearly increased in wk 3, 6, 9, and 12. Additionally, Haugh unit and albumen height were improved in wk 12. Cufadar et al. (2010) found that xylanase addition to corn- or wheat-SBM-based diets had no significant effect on yolk index, albumen index, Haugh unit, or yolk color in White Leghorn LSL laying hens between 52 and 64 wk of age. Pirgozliev et al. (2010) noted that inclusion of xylanase (0, 400, 800, 1200, and 1600 U/kg, respectively) in wheat-SBM-rye-based diet linearly increased yolk color, but shell color, albumen height, Haugh unit, and shell thickness were not affected in Lohmann Brown laying hens between 28 and 32 wk of age. Scheideler et al. (2005) observed that enzyme (xylanase, protease, and α-amylase) supplementation had no effect on Haugh unit or percentages of egg albumen, yolk, and shell, whereas yolk lightness was reduced in laying hens fed corn-SBM-based diets. Silversides et al. (2006) indicated that xylanase increased albumen height in laying hens fed diets with adequate phosphorus but not in those fed phosphorus-reduced diets. In agreement with our results, Mirzaie et al. (2012) observed that xylanase increased shell thickness in laying hens fed corn-SBM-wheat-based diets. The effectiveness of xylanase in improving eggshell thickness may be associated with the utilization of minerals. It is conceivable that the in situ production of arabinoxylan-oligosaccharides from hydrolysis of arabinoxylan results in the changes in intestinal pH and microbiota and therefore improves solubility and absorption of calcium (Damen et al., 2012; Li et al., 2017; Wang et al., 2017). The reason for the increased Haugh unit and albumen height is difficult to provide. Further experiments are required to explain the exact mechanism by which xylanase supplementation affects egg quality. In conclusion, the results of this study suggest that xylanase supplementation in corn-SBM-wheat-based diets could shift microbiota by increasing excreta lactic acid bacteria and improve egg quality indicated as increased eggshell thickness, Haugh unit and albumen height. 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Poultry ScienceOxford University Press

Published: Mar 1, 2018

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