The effects of enzyme supplementation on performance and digestive parameters of broilers fed corn-soybean diets H. L. Zhu, L. L. Hu, Y. Q. Hou, J. Zhang, and B. Y. Ding1 Hubei Key Laboratory of Animal Nutrition and Feed Science, Wuhan Polytechnic University, Wuhan 430023, China activity, but reduced pancreatic lipase (d 14, P = 0.03; d 21, P = 0.004) and amylase (d 14, P = 0.027) activity. Enzyme supplementation resulted in an increase in pancreatic amylase (d 7, P = 0.023), trypsin (d 7, P = 0.02; d 21, P = 0.004), lipase (d 21, P = 0.001), pepsin (d 7, P = 0.001; d 14, P = 0.004; d 21, P = 0.001), and maltase (d 14, P = 0.011, in ileum) activity. Moreover, broilers fed low dietary ME and enzyme supplementation diets had an increase in pancreatic lipase (d 21, P = 0.001) and pepsin (d 7, P = 0.001) activity. Low ME diets reduced jejunum villus height and jejunum and ileum crypt depth (d 7, 21). However, enzyme supplementation, especially enzyme supplementation in low ME diets, increased jejunum and ileum villus height and villus surface area. This suggested enzyme supplemented with low ME diet might be more effective to improve the activity of digestive enzymes and the absorptive capacity of the small intestine.

Key words: broiler, enzyme supplementation, dietary metabolizable energy level, growth performance, digestive parameter 2014 Poultry Science 93:1704–1712 http://dx.doi.org/10.3382/ps.2013-03626

INTRODUCTION Broilers have a limited ability to effectively use diets containing lower-quality ingredients with high fiber content. Cereals such as wheat, barley, oats, rye, and their by-products contain a high proportion of partly soluble dietary fiber polysaccharide residues (nonstarch polysaccharides, NSP), which depress growth in broiler chickens (Wang et al., 1992). However, supplementation of exogenous enzymes to cereal-based diets is often followed by improved performance (Cowieson, 2005; Wang et al., 2005; Francesch and Geraert, 2009). Thus, enzyme supplementation has become increasingly popular in poultry feeds. It is well documented that the inclusion of a high level of NSP in cereal-based diets has been shown to ©2014 Poultry Science Association Inc. Received September 16, 2013. Accepted April 14, 2014. 1 Corresponding author: [email protected]

inhibit the digestion of starch and other nutrients by causing an increase in the viscosity of the digesta (Campbell and Bedford, 1992). The beneficial effects of enzyme supplementation of poultry diets based on viscous cereals are well established (Annison, 1992; Bedford and Classen, 1992). For low viscosity ingredients, such as corn and soybean meal, it was thought that enzyme supplementation would not be beneficial. The nutrients contained in corn and soybean meal are generally considered to be highly digestible (Zanella et al., 1999; Maisonnier-Grenier et al., 2004). However, corn contains approximately 0.9% soluble NSP and 6 to 8% insoluble NSP, whereas soybean meal contains approximately 6% soluble NSP and 18 to 21% insoluble NSP (Bach Knudsen, 1997; Choct, 2006). Brown (1996) found that some of the starch in corn is resistant to digestion. The energy utilization in corn and soybean meal depends on starch and the amount of indigestible carbohydrates in NSP (Kocher et al., 2003). Most studies indicated that enzyme mixture may have improved

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ABSTRACT The study was performed to evaluate the effects of enzyme supplementation on performance and digestive parameters of broilers fed corn-soybean diets from 1 to 21 d of age. A total of 480 one-day-old Cobb broilers were allocated to 1 of 4 treatments, with 6 replicate pens per treatment and 20 birds per pen. The experiment consisted of a 2 × 2 factorial arrangement of treatments with 2 dietary ME levels (high ME, energy 1, 12.13 MJ/kg or low ME, energy 2, 11.92 MJ/kg) and 2 levels of supplemental enzyme (including xylanase, 1,800 IU/g, β-glucanase, 500 IU/g, and α-amylase, 800 U/g; 0 or 0.1% of diet). Enzyme supplementation had no effect on average daily weight gain, feed intake, and feed:gain. However, enzyme supplementation decreased the relative weight of the pancreas (d 7 and 21) in broilers fed the high ME diet. Low dietary ME level increased pancreatic lipase (d 7, P = 0.015), trypsin (d 14, P = 0.01; d 21, P = 0.014), amylase (d 21, P = 0.027), and pepsin (d 7, P = 0.001; d 21, P = 0.042)

EFFECTS OF ENZYME SUPPLEMENTATION

MATERIALS AND METHODS Experimental Design and Diets Four hundred eighty 1-d-old Cobb broilers of mixed sex were purchased from a commercial hatchery. The birds were randomly allocated to 24 pens, each containing 20 chicks. Light was continuous during the experiment and temperature was gradually reduced from 33 to 22°C until d 21. Chickens had access to feed in mash form and water ad libitum. All chickens were inoculated with infectious bursa disease vaccine on d 14 and 21, and with Newcastle disease and infectious bronchitis vaccine on d 7. All animal procedures were approved by the Animal Care and Use Committee of Hubei Province, China. A 2 × 2 factorial arrangement of treatments was used in a randomized complete block design to study the effects of 2 ME energy levels (high ME, energy 1, 12.13 MJ/kg or low ME, energy 2, 11.92 MJ/kg), enzyme supplementation (none or enzyme mixture supplement), and their interactions. Six blocks, 4 experimental units within a block, and 6 replicates per treatment were used. Each replicate consisted of 20 birds, for a total of 120 birds per treatment. The composition of the experimental basal diet is shown in Table 1. The enzyme preparation was a multicarbohydrase cocktail and supplied xylanase (1,800 IU/g), β-glucanase (500 IU/g), and α-amylase (800 U/g). Enzymes were added according to the supplier’s recommendation (0.1% of diet). The enzyme preparation was provided by Wuhan Xinhuayang Biologic Ltd. of China.

Growth Performance The experiment lasted for 21 d. On d 7, 14, and 21, chickens were weighed by pen, and feed consumption

was recorded. Average daily weight gain, ADFI, and feed:gain were calculated for the periods 0 to d 7, d 8 to 14, d 15 to 21, and for the overall experiment.

Collection of Sample At d 7, 14, and 21, 6 chickens per treatment (one chicken from each pen) were randomly selected, weighed, and killed by cervical dislocation. The proventriculus, gizzard, pancreas, and liver were removed and weighed. The intestinal tract was immediately excised and the following segments were collected: duodenum (pancreatic loop), jejunum (from the pancreatic loop to Meckel’s diverticulum), ileum (from Meckel’s diverticulum to the ileocecal junction for measurement of the length and weight. A 1-to 2-cm-long cross-section of intestinal tissue was obtained from the midjejunum and midileum, washed with physiological saline solution, and fixed in 4% paraformaldehyde in PBS for intestinal morphology measurement. The proventriculus, pancreas, and a 5-cm segment of the small intestine (jejunum and ileum) were cleaned and homogenized in ice-cold PBS (pH 7.2–7.4). The homogenates were then centrifuged at 20,000 × g for 30 min at 4°C, and the supernatant was collected and stored at −70°C for enzyme assays.

Digestive Enzyme Analysis The samples of proventriculus, pancreas, and intestine were thawed for determination of enzyme activities. Digestive enzymes included gastric pepsin (EC 3.4.23.1); pancreatic lipase (EC 3.1.1.3), amylase (EC 3.2.1.1), and trypsin (EC 3.4.21.4); and intestinal sucrase (EC 3.2.1.48) and maltase (EC 3.2.1.20). The HCl (pH 2) was added to the gastric homogenates and allowed to convert the gastric pepsinogen into pepsin. Trypsinogen in pancreatic homogenates was activated using the procedure described by Glazer and Steer (1977). The activities of digestive enzymes in gastric and pancreatic homogenates were analyzed by a microplate reader (SpectraMax M5, Molecular Devices, Sunnyvale, CA) using diagnostic kits (Nanjing Jiancheng Bioengineering Institute, Nanjing, China) according to the instructions of the manufacturer. The maltase and sucrase were assayed with maltose and sucrose as a substrate at pH 6.4. Released glucose was determined by the glucose-oxidase method (Bergmeyer, 1985). The protein concentrations were determined using the Coomassie Brilliant Blue G-250 reagent with BSA as a standard, and enzyme activities were expressed as units per gram of protein.

Intestinal Morphology Fixed intestinal samples were dehydrated with graded ethanol solutions (50, 70, 80, 95, and 100%), cleared with xylene, and embedded in paraffin. Histological slides were prepared from 3 cross-sections (4 μm thick)

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digestion of some starch fraction (Zanella et al., 1999) and significantly increased NSP digestibility and ME by degrading cell wall polysaccharides of corn and soybean meal (Kocher et al., 2003; Meng et al., 2005; Francesch and Geraert, 2009). Therefore, use of an enzyme mixture allowed a reduction in the energy formulation of the diets (Zanella et al., 1999; Aftab, 2009). Several studies demonstrated that enzyme treatment can affect the intestinal morphology in birds fed barley-based diets. Improved digestive efficiency cannot be attributed only to morphological change in the gastrointestinal tract. In fact, the digestive process is highly dependent on endogenous enzyme activity (Osman, 1982; Pubols, 1991). However, little is known about the effect of enzyme supplementation on intestinal morphology and digestive enzyme activity in broiler fed corn soybean-based diets. Thus, the objective of this investigation was to determine the effects of different dietary ME levels and enzyme mixture supplementation in corn-soybean meal diets for broilers on performance, intestinal morphology, and digestive enzyme activity.

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Zhu et al. Table 1. Composition of experimental diets (as-fed basis) ME level Energy 1 Item  

56.15 33.0 2.0 3.0 2.0 1.45 1.35 0.17 0.07 0.10 0.30 0.05 0.05 0.20 0.04 0.02 0.05 0.00 0.00   12.13 20.50 1.0 0.45   89.17 20.48 38.35 3.09 6.52 7.98 6.12 5.96

+Enzyme  

56.15 33.0 2.0 3.0 2.0 1.45 1.35 0.17 0.07 0.10 0.30 0.05 0.05 0.20 0.04 0.02 0.05 0.00 1.0   12.13 20.50 1.0 0.45   88.87 20.51 38.35 3.11 6.52 7.98 6.12 5.97

–Enzyme  

56.15 33.0 2.0 2.92 2.0 1.45 1.35 0.17 0.07 0.10 0.30 0.05 0.05 0.20 0.04 0.02 0.05 0.08 0.00   11.92 20.40 1.0 0.45   89.19 20.47 38.33 3.08 6.52 7.98 6.04 5.97

+Enzyme  

56.15 33.0 2.0 2.92 2.0 1.45 1.35 0.17 0.07 0.10 0.30 0.05 0.05 0.20 0.04 0.02 0.05 0.08 1.0   11.92 20.40 1.0 0.45   88.87 20.50 38.33 3.09 6.52 7.98 6.04 5.97

1Mineral premix provided per kilogram of diet: Fe, 80 mg (FeSO ); Cu, 10 mg (CuSO ); Mn, 60 mg (MnSO ); 4 4 4 Zn, 40 mg (ZnSO4); I, 0.35 mg (KI); Se, 0.15 mg (Na2SeO3). 2Vitamin premix provided per kilogram of diet: retinol, 1,500 IU; cholecalciferol, 2,000 IU; dl-α-tocopheryl acetate, 50 IU; menadione, 4 mg; thiamine, 6 mg; riboflavin, 12 mg; pyridoxine 6 mg; cobalamin, 0.05 mg; biotin, 0.2 mg; folic acid, 2 mg; niacin, 50 mg; d-calcium pantothenate, 25 mg. 3Enzymes were formulated into the premix at 1 g/kg of diet. 4In duplicate samples.

of each intestinal sample and stained with hematoxylin and eosin. The villus height was measured from the villus tip to the valley between individual villus. The crypt depth and width was measured from the valley between individual villus to the basolateral membrane. The 10 longest and straightest villi and associated crypts were measured from each segment (Xu et al., 2003). Mean villus height, crypt depth, and villus width were calculated and used for statistical analysis. Villus surface area was calculated from villus height and width data (Nunez et al., 1996).

Statistical Analysis Data were analyzed by ANOVA using the GLM procedures of SAS (SAS Institute Inc., Cary, NC) appropriate for a 2 × 2 factorial design. The statistical model included the effects of dietary ME levels, enzyme addition, and their interactions. For difference between treatments was analyzed using a t-test following a sig-

nificant F-test. The differences were considered significant at P < 0.05.

RESULTS Growth Performance The results of growth performance for broilers during the 3-wk experiment are shown in Table 2. The ADFI, ADG, and feed:gain were not significantly affected (P > 0.05) by dietary ME level or enzyme supplementation. Overall, from 1 to 21 d, dietary ME level and enzyme supplementation did not affect broiler growth performance. There was no significant interaction the effect of dietary ME level and enzyme supplementation.

Relative Organ Weights The effects of dietary ME level and enzyme addition on relative weight (% of BW) of selected digestive

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Ingredient, %  Corn   Soybean meal   Fish meal   Soybean oil   Cottonseed meal  Limestone   Dicalcium phosphate   l-Lysine∙HCl (98%)   dl-Methionine (98%)   Choline chloride (50%)  Salt   Calcium propionate   Ethoxyquin (33%)   Mineral premix1   Vitamin premix2   Conlistin sulfate premix (10%)   Narasin premix (12%)   Zeolite powder  Enzyme,3 g/kg of diet Calculated nutrient   ME, MJ/kg   CP, %   Ca, %   Available P, % Determined analysis4   DM, %   CP, %   Starch, %   Crude fiber, %   Neutral detergent fiber, %   Acid detergent fiber, %   Ether extract, %   Total ash, %

–Enzyme

Energy 2

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EFFECTS OF ENZYME SUPPLEMENTATION Table 2. Effects of dietary ME and enzyme addition on growth performance of broilers fed corn-soybean diets1 Energy 1 Item

1Data

P-value

–Enzyme2

+Enzyme2

–Enzyme2

+Enzyme2

SEM

Energy

Enzyme

Interaction

47.8   16.8 13.7 1.23   35.9 24.0 1.50   80.1 50.3 1.60   44.4 29.4 1.51

46.8   16.9 14.6 1.16   36.3 25.1 1.45   75.6 50.9 1.49   42.9 30.2 1.43

46.0   17.5 14.0 1.25   34.4 23.4 1.47   80.0 47.8 1.68   43.9 28.4 1.55

47.5   15.3 12.9 1.17   34.8 23.3 1.49   78.8 50.5 1.57   42.4 28.6 1.48

0.84   0.49 0.33 0.02   0.95 1.41 0.03   1.15 0.66 0.03   0.84 0.45 0.02

—   0.64 0.28 0.64   0.48 0.16 0.97   0.52 0.29 0.16   0.78 0.16 0.30

—   0.33 0.91 0.073   0.83 0.55 0.80   0.24 0.23 0.067   0.42 0.61 0.096

—   0.25 0.13 0.89   0.98 0.50 0.65   0.49 0.43 0.98   0.97 0.79 0.89

are means of 6 pens of 20 broilers each. added to the diets were 0 and 0.1% of diet.

2Enzymes

organs and intestinal length are presented in Table 3. There was a significant interaction (P = 0.045) between dietary ME level and enzyme supplementation on the relative weight of the pancreas on d 7 and 21. Enzyme supplementation decreased the relative weight of the pancreas in broilers fed the high ME diet (energy 1). For the low ME diet (energy 2), enzyme supplementation did not affect the weight of the pancreas. In addition, high ME diets increased the relative weight of the liver (P = 0.026) on d 7. However, relative sizes of proventriculus, gizzard, and intestine were not affected by dietary ME level or enzyme supplementation. On d 14, the relative weight of the gizzard was higher (P = 0.013) in broilers fed high ME diets compared with broilers fed low ME diets. On d 21, enzyme supplementation increased the relative weight of the proventriculus (P = 0.029). Broilers fed high ME diets had higher relative sizes of liver (P = 0.011) and duodenum (P = 0.022) than those fed low ME diets. However, no interactions were observed between dietary ME level and enzyme supplementation.

Pancreatic Enzymes and Pepsin Data on the digestive enzyme activities in pancreas are presented in Table 4. On d 7, pancreatic lipase activity was higher (P = 0.015) in broilers fed the low ME diet compared with broilers fed the high ME diet. Broilers fed enzyme-supplemented diets had lower pancreatic lipase activity (P = 0.001) and trypsin activity (P = 0.02) than broilers fed non-enzyme-supplemented diets. Pancreatic amylase activity was higher (P = 0.023) in enzyme-supplemented broilers than that of nonsupplemented broilers. On d 14, broilers fed diets with the low ME level had lower pancreatic lipase (P = 0.03) and amylase activity (P = 0.005) than broilers fed diets with the high ME level. Furthermore, enzyme supplementation decreased pancreatic amylase activity

(P = 0.001). However, both low dietary ME level (P = 0.01) and enzyme supplementation (P = 0.05) increased pancreatic trypsin activity. On d 21, low ME diet decreased pancreatic lipase activity (P = 0.004). An interaction was observed between dietary ME level and enzyme supplementation in pancreatic lipase activity (P = 0.002). Enzyme supplementation increased pancreatic lipase activity in broilers fed the low ME diet. For the high ME diet, enzyme supplementation did not affect the activity of pancreatic lipase. Pancreatic amylase (P = 0.03) and trypsin activity (P = 0.01) were higher in broilers fed low ME diets compared with broilers fed high ME diets. Enzyme supplementation enhanced pancreatic trypsin activity (P = 0.004). There was no interaction between dietary ME level and enzyme supplementation on pancreatic amylase and trypsin activity (P > 0.05). On d 7 and 21, pepsin activity was higher (P = 0.015) in broilers fed low ME diets compared with broilers fed high ME diets. There was an interaction between dietary ME level and enzyme supplementation on pepsin activity on d 7. Enzyme supplementation increased pepsin activity in broilers fed the low ME diet. For the high ME diet, enzyme supplementation did not affect the activity of pepsin. Furthermore, broilers fed enzyme-supplemented diets had higher pepsin activity (d 14, P = 0.004; d 21, P = 0.001) than broilers fed non-enzyme-supplemented diets.

Intestinal Enzymes There was interaction between dietary ME level and enzyme supplementation on sucrase activity on d 7 in the jejunum (Table 5). Enzyme supplementation decreased sucrase activity in broilers fed the high ME diet. For the low ME diet, enzyme supplementation did not affect the activity of sucrase in the jejunum. In addition, high ME diets increased jejunal maltase

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Initial BW, g 1–7 d   ADFI, g   ADG, g   Feed:gain, g:g 8–14 d   ADFI, g   ADG, g   Feed:gain, g:g 15–21 d   ADFI, g   ADG, g   Feed:gain, g:g 1–21 d   ADFI, g   ADG, g   Feed:gain, g:g

Energy 2

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Table 3. Effects of dietary ME and enzyme addition on relative weight (% BW) of selected digestive organs and intestinal length of broilers fed corn-soybean diets1 Energy 1 Item

–Enzyme2

+Enzyme2

–Enzyme2

P-value

+Enzyme2

SEM

Energy

Enzyme

Interaction

2.78 0.45a 0.93 3.95

2.78 0.37b 0.87 4.01

2.98 0.39ab 0.93 4.10

3.06 0.40ab 0.98 4.15

0.054 0.011 0.027 0.096

0.026 0.46 0.35 0.49

0.70 0.093 0.98 0.80

0.68 0.045 0.33 0.98

2.46 0.36 0.68 2.93

2.59 0.35 0.63 3.08

2.32 0.35 0.61 2.86

2.46 0.35 0.58 2.63

0.045 0.010 0.016 0.057

0.12 0.83 0.079 0.013

0.13 0.87 0.25 0.65

1.0 0.86 0.89 0.056

2.08 0.41a 0.50 2.21

2.05 0.34b 0.55 2.45

2.29 0.34b 0.46 2.15

2.29 0.36ab 0.53 2.24

0.044 0.010 0.013 0.045

0.011 0.13 0.18 0.11

0.81 0.22 0.029 0.055

0.87 0.019 0.62 0.35

9.25 17.01 12.81

9.21 16.26 11.69

9.67 14.86 12.56

8.70 17.39 12.11

0.29 0.57 0.50

0.94 0.62 0.94

0.42 0.39 0.48

0.46 0.12 0.76

5.57 9.51 6.99

5.39 9.89 7.59

6.10 11.71 8.53

5.60 9.69 7.57

0.13 0.34 0.22

0.15 0.11 0.064

0.18 0.18 0.64

0.51 0.059 0.058

2.99 5.67 4.57

2.79 5.78 4.79

2.59 5.91 4.66

2.36 5.54 4.23

0.094 0.14 0.12

0.022 1.0 0.33

0.22 0.68 0.65

0.91 0.42 0.18

a,bValues

in a row with different superscripts differ significantly (P < 0.05). are means of 6 pens of 6 broilers each. 2Enzymes added to the diets were 0 and 0.1% of the diet. 1Data

(d 14, P = 0.012) activity. Enzyme supplementation decreased maltase (d 7, P = 0.023) and sucrase activity (d 21, P = 0.014) in the jejunum. In the ileum, there was interaction between dietary ME level and enzyme supplementation in maltase activity on d 14 and 21. Enzyme supplementation increased maltase activity in broilers fed the low ME diet. For the high

ME diet, enzyme supplementation did not affect the activity of maltase in the ileum. Broilers fed enzymesupplemented diets had lower sucrase activity (d 21, P = 0.006) than broilers fed non-enzyme-supplemented diets. Broiler fed low ME diets had a decrease (P = 0.012) in sucrase activity (d 7) compared with broilers fed high ME diets.

Table 4. Effect of dietary ME and enzyme addition on pancreatic digestive enzyme activities (U/mg of protein) of broilers fed cornsoybean diets1 Energy 1 Item Pancreas, 7 d  Lipase  Amylase  Trypsin Pancreas, 14 d  Lipase  Amylase  Trypsin Pancreas, 21 d  Lipase  Amylase  Trypsin   Pepsin, 7 d   Pepsin, 14 d   Pepsin, 21 d a,bValues

Energy 2

–Enzyme2

+Enzyme2

–Enzyme2

+Enzyme2

SEM

Energy

Enzyme

Interaction

0.93 321 363

0.59 465 423

1.27 393 351

0.75 512 316

0.087 54 15

0.015 0.25 0.89

0.001 0.023 0.02

0.099 0.89 0.066

0.43 345 351

0.81 225 319

0.36 246 436

0.35 139 420

0.106 27 56

0.03 0.005 0.01

0.1 0.001 0.005

0.094 0.80 0.38

1.02a 186 360 4.60b 7.60 4.32

1.22a 197 392 4.73b 13.19 7.56

0.53b 292 493 4.68b 9.38 6.01

1.24a 295 514 9.74a 17.71 8.28

0.067 42 103 0.57 1.31 0.444

0.004 0.027 0.014 0.001 0.15 0.042

0.001 0.87 0.004 0.001 0.004 0.001

0.002 0.98 0.33 0.005 0.52 0.38

in a row with different superscripts differ significantly (P < 0.05). are means of 6 replicates of 6 broilers each. 2Enzymes added to the diets were 0 and 0.1% of the diet. 1Data

P-value

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Relative weight, 7 d  Liver  Pancreas  Proventriculus  Gizzard Relative weight, 14 d  Liver  Pancreas  Proventriculus  Gizzard Relative weight, 21 d  Liver  Pancreas  Proventriculus  Gizzard Relative length, 7 d  Duodenum  Jejunum  Ileum Relative length, 14 d  Duodenum  Jejunum  Ileum Relative length, 21 d  Duodenum  Jejunum  Ileum

Energy 2

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EFFECTS OF ENZYME SUPPLEMENTATION

Table 5. Effect of dietary ME and enzyme addition on mucosal enzyme activity (U/mg of protein) of maltase and sucrase in small intestinal segments of broilers fed corn-soybean diets1 Energy 1 Item

P-value

–Enzyme2

+Enzyme2

–Enzyme2

+Enzyme2

SEM

Energy

Enzyme

Interaction

1.23a 14.28

0.85b 13.59

0.74b 14.18

0.83b 12.08

0.066 0.324

0.032 0.17

0.20 0.023

0.047 0.22

0.55 14.31

0.59 14.79

0.65 13.44

0.48 13.21

0.04 0.247

0.99 0.012

0.44 0.76

0.21 0.42

2.08 19.56

1.20 20.35

2.17 17.48

1.67 20.79

0.145 0.608

0.26 0.50

0.014 0.11

0.45 0.31

1.12 15.97

0.93 16.98

0.83 15.63

0.58 15.29

0.068 0.434

0.012 0.29

0.068 0.72

0.76 0.47

0.72 16.76ab

1.02 17.07a

1.05 15.45b

0.80 19.74a

0.068 0.513

0.65 0.41

0.87 0.011

0.052 0.025

0.94 22.42a

0.32 19.34ab

0.71 18.11b

0.50 22.25a

0.081 0.579

0.81 0.41

0.006 0.53

0.14 0.001

a,bValues

in a row with different superscripts differ significantly (P < 0.05). are means of 6 replicates of 6 broilers each. 2Enzymes added to the diets were 0 and 0.1% of the diet. 1Data

Intestinal Morphology The effect of dietary ME level and enzyme supplementation in corn-soybean diets on broiler intestinal morphology for d 7, 14, and 21 are shown in Table 6. In the jejunum, there was an interaction between dietary ME level and enzyme supplementation in villus height (d 7, d 21) and villus width and area (d 14). Enzyme supplementation increased villus width and area in broilers fed the high ME diet and villus height in broilers fed the low ME diet. For the low ME diet, enzyme supplementation did not affect villus area, but reduced villus width. Furthermore, enzyme supplementation increased villus height (d 14, P < 0.001) and villus area (d 7, P < 0.001), and decreased crypt depth (d 21, P = 0.007) and villus width (d 21, P = 0.049). The high ME diet enhanced crypt depth (d 7, P < 0.001; d 14, P = 0.001), but reduced villus area (d 21, P = 0.024) on d 21. In the ileum, there was an interaction between dietary ME level and enzyme supplementation in villus height (d 7, 14), crypt depth (d 7, 14), villus width (d 7, 14), and villus area (d 7). Enzyme supplementation increased villus height (d 7), crypt depth (d 7), and villus width (d 7 and 14) and area (d 7) in broilers fed the low ME diet and villus height (d 14) and crypt depth (d 14) in broilers fed the high ME diet. For the high ME diet, enzyme supplementation did not affect crypt depth (d 7) and villus width and area (d 7). Moreover, the effects of dietary ME level and enzyme supplementation on ileal villus height, crypt depth, and villus width and area were similar to those in the jejunum.

DISCUSSION In commercial broiler production, the benefits of exogenous enzyme supplementation to NSP-rich diets are

well documented (Bedford and Classen, 1992; Almirall et al., 1995; Yu et al., 1997). However, in China, corn and soybean meal are the major ingredients supplying energy and protein in commercial broiler diets because corn and soybean meal are generally considered to be highly digestible (Zanella et al., 1999; Maisonnier-Grenier et al., 2004) and provide the majority of these nutrients, respectively. Traditional thought would suggest that these diets, based on corn and soybeans, would not be improved by enzyme supplementation. In general, the ME level of corn-soybean meal diets depends on the digestibility of starch, NSP, and protein. Starch is the major energy source in corn. Brown (1996) found that digestion of starch in the small intestine is incomplete, suggesting that some of the starch was indeed resistant. Soybean meal contains nondigestible carbohydrates, which could be available to broilers with proper enzyme supplementation (Cowan, 1993). Therefore, there is some room for improvement of the corn and soybean meal nutritional value (Zanella et al., 1999; MaisonnierGrenier et al., 2004). Zanella et al. (1999) indicated that exogenous enzyme supplementation of broiler diets based on corn and soybeans improved the digestibility of the nutrients and broiler performance. Moreover, enzyme supplementation allowed a reduction in the energy formulation of the diets. The present study demonstrated that enzyme supplementation had no major effects on ADG, ADFI, and feed:gain. The reason might be that the study lasted only 21 d. However, the effects of enzyme could extend to the overall growth period. Similarly, previous studies showed that enzyme addition to the corn-soybean diet did not affect chick performance (Marsman et al., 1997; Douglas et al., 2000; Kocher et al., 2002; Meng and Slominski, 2005). In contrast, several reports indicated substantial BW and feed conversion improvements because of enzyme supplementation

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Jejunum, 7 d  Sucrase  Maltase Jejunum, 14 d  Sucrase  Maltase Jejunum, 21 d  Sucrase  Maltase Ileum, 7 d  Sucrase  Maltase Ileum, 14 d  Sucrase  Maltase Ileum, 21 d  Sucrase  Maltase

Energy 2

1710

Zhu et al.

Table 6. Effect of dietary ME and enzyme addition on intestinal morphology of broilers fed corn-soybean diets1 Energy 1 Item

+Enzyme2

–Enzyme2

P-value

+Enzyme2

SEM

Energy

Enzyme

Interaction

541c 130 93 159

760b 141 152 367

518c 75 102 167

881a 88 147 407

36 6.78 7.71 29

0.037

The effects of enzyme supplementation on performance and digestive parameters of broilers fed corn-soybean diets.

The study was performed to evaluate the effects of enzyme supplementation on performance and digestive parameters of broilers fed corn-soybean diets f...
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