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METABOLISM AND NUTRITION |
* Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061; and Danisco Animal Nutrition, 780 W Army Trail Rd #192, Carol Stream, IL 60188
1 Corresponding author: cnovak{at}vt.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Key Words: poult • Avizyme 1502 • performance • ileal digestibilities • morphology
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Enzyme supplementation may be especially applicable to young birds, given that brush border disaccharidases are not fully functional (Sell et al., 1989) upon hatch. Wyatt et al. (1999) observed that the addition of Avizyme 1500 (AZ1500) led to a 3.3% increase in average ileal energy content and reduced variation between samples in terms of energy content. Gracia et al. (2003) reported that 
-amylase supplementation of corn-SBM diets increased average daily gain, feed intake (FI), and AMEn through 42 d. Avizyme 1502 was formulated to improve energy utilization in corn-SBM and sorghum-SBM diets. The bacterially derived enzyme product contains amylase, xylanase, and protease to promote the breakdown of starch, cell walls, storage proteins, and proteinaceous antinutritional factors, respectively. Pekin ducks fed corn-SBM diets supplemented with AZ1502 experienced a 6 to 8% increase in BW gain as well as improvements in feed efficiency over a 42-d period, compared with ducks on an unsupplemented control diet (Hong et al., 2002).
Although Avizyme has been shown to improve bird performance and digestibility, the literature is inconsistent concerning the degree of improvement. Ritz et al. (1995) reported improvements in the growth of poults fed low-protein diets with the addition of AZ1500. Similarly, Café et al. (2002) reported BW gain improvements in broilers fed corn-SBM diets supplemented with AZ1500. Increased feed digestibility is usually associated with increased feed consumption. Scott et al. (2003) observed that feed consumption was increased in both wheat-and corn-based diets upon addition of AZ1500. These reported improvements were inconsistent in terms of feed consumption ratio (FCR), most likely because of increased feed consumption, low BW gains, or a combination of the two.
Douglas et al. (2000) observed improvements in ileal digestibilities with AZ1500; however, there were no corresponding production improvements. Iji et al. (2003) reported increased BW gain over 28 d with no effects on energy, protein, calcium, or amino acid digestibility. Zanella et al. (1999) reported an enhancement of production traits and CP digestion with AZ1500 supplementation. Increased digestibility, however, was not equal for all amino acids.
Diet composition is an influential factor in endogenous enzyme activity (Sell et al., 1989), with a positive correlation between mucosal area and villus height (Keelan et al., 1985). Mucosal hydrolysis is highly correlated with BW and is thought to be a potential limiting step in digestion (Uni et al., 1999). Therefore, exogenous enzymes may also have a positive effect on nutrient absorption through mucosal activity, an activity that may be reflected by villus height. Furthermore, villus size and mucosal activity are initially lower in poults (Uni et al., 1999) than in broilers, suggesting the potential for enzymes to improve early poult performance. Thus, the objective of the experiment reported herein was to study the effects of AZ1502 on turkey poults (0 to 56 d) fed industry-based corn-SBM diets. We hypothesized that a lower energy diet supplemented with 500 g/tonne (industry recommended) of enzyme would match the positive control (PC) in terms of production, digestibility, and small intestinal morphology.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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) for a prestarter (0 to 21 d of age), starter 1 (21 to 42 d of age), and starter 2 (42 to 56 d of age). All diets were formulated to be isocaloric and isonitrogenous. Chromic oxide was included in all diets at a 0.3% inclusion rate as an inert marker throughout the duration of the trial. The negative control (NC) diet was formulated based on the average increase in energy availability from US corn (2004) with the use of AZ1502 (Danisco Animal Nutrition, Copenhagen, Denmark). Avizyme 1502 is composed of xylanase, Trichoderma longibrachiatum (600 units/g), protease, Bacillus subtilis (8,000 units/g) and amylase, and Bacillus amyloliquofaciens (800 units/g). The AZ1502 was expected to increase ME from corn by 140 kcal/kg, so the matrix value for ME was increased from 3,418 to 3,558 kcal/kg as fed. The actual gross energy drops between the PC and NC diets for the prestarter, starter 1, and starter 2 periods were 69.1, 97.0, and 53.1 kcal/kg, respectively. Additional dietary treatments consisted of the NC diet supplemented with AZ1502 at 250, 500, and 750 g/tonne.
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Apparent Ileal Digestibilities
On d 4 (n = 19/pen), 8 (n = 14/pen), 12 (n = 14/pen), 16 (n = 9/pen), 21 (n = 9/pen), 42 (n = 4/pen), and 56 (n = 4/pen), birds were killed by cervical dislocation prior to sample collection. Ileal sections, defined as the region from the Meckel’s diverticulum to the ileocecal junction, were immediately harvested and their contents obtained through squeezing. Apparent ileal digestibilities of both energy and protein were estimated using Cr2O3 as an inert dietary marker. Prior to analysis, ileal contents were frozen, freeze-dried (Labconco FreeZone Plus12 at –10°C for 48 h; Labconco Corp., Kansas City, MO), and then ground using a Wiley Mini Mill (Thomas Scientific, Swedesboro, NJ) with a 40-mesh screen. Diet and ileal samples were prepared according to Williams et al. (1962) and Cr2O3 levels were analyzed using atomic absorption spectrometry (PerkinElmer AAnalyst 800 spectrometer; PerkinElmer Inc., Wellesley, MA). Samples were also analyzed in duplicate for gross energy (cal/g) by bomb calorimetry (Parr 1271 automatic bomb calorimeter; Parr Instrument Company, Moline, IL) and nitrogen percentage by the combustion method according to AOAC (1990), which went toward calculating energy and protein digestibility. Apparent digestibly was calculated using the following equation (Williams et al., 1962):
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where nutrient, in this case, refers to either energy or protein.
Intestinal Morphology
At 4, 8, 12, 16, 21, 42, and 56 d, an additional bird per pen (n = 7/treatment) was killed by cervical dislocation and 5-cm sections of the ascending duodenum (prior to the pancreatic bile ducts), jejunum (medial portion posterior to the bile ducts and anterior to the Meckel’s diverticulum), and ileum (medial portion posterior to the Meckel’s diverticulum and anterior to the ileocecal junction) were removed, rinsed in Tris-buffered saline (Sun et al., 2005), cut into 5 equal pieces and fixed in 10% neutral buffered formalin. Each intestinal piece was subsequently cut into 5-mm sections and placed into cassettes. Cassettes were sent to Histo-Scientific Research Laboratories (Woodstock, VA) embedded in paraffin, cut into thicknesses of 5 µm, and mounted onto slides. Tissue slides were returned to Virginia Tech and subsequently stained using 0.02% toluidine blue (Churukian and Schenk, 1981). Pictures were obtained using an Olympus DP 70 camera (magnification 40x; Olympus America Inc., Melville, NY) mounted on a BX50 photomicroscope (Olympus America Inc.). After 16 d, duodena became too large to view on the photomicroscope. When this occurred, an Olympus DP 10 camera (magnification 20 or 40x) mounted on a SZ60 dissecting scope (Olympus America Inc.) was used. Cameras were calibrated using a micrometer to ensure the proper scale, and all measurements were made using SigmaScan Pro 5 (SPSS Inc., Chicago, IL). Measurements were made by visually dividing the mucous membrane into villi and crypts. Villi were measured from the tip of the luminal projection to the top of the crypts. Crypts were measured from the bottom of the villi to the submucosa. Measurements of villus height and crypt depth were obtained for the duodenum (magnification 20x), jejunum, and ileum (magnification 40x). Three of the 5 possible tissue samples were selected at random for villus height and crypt depth measurements. All reported villi and crypt values were an average of 4 measurements per tissue (n = 12 measurements/bird, 3-segment averages/bird, 7 birds/treatment; Sun et al., 2005).
Statistical Analysis
Production and digestibility data were analyzed through the MIXED procedure of SAS (1999; SAS Institute, Cary, NC) for a randomized complete block design, with pen representing the experimental unit. The statistical model was
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where yij is the observed dependent variable, µ is the grand mean (pen average), i is the ith dietary treatment effect, ßj is the jth random block effect, and 
ij is the error for treatment i of block j ~ N (0, 
). The least squares means procedure of SAS was used to calculate dietary treatment means, with significance established at P 
0.05. The PROC FREQ function of SAS was used to analyze mortality. Villus heights and crypt depths were evaluated using the MIXED procedure of a 2-factorial design with days of age and diet as factors. The model was
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where yijk is the observed dependent variable, µ is the grand mean, i is the days of age treatment effect for level i, ßj is the dietary treatment effect for level ßj, (ß)ij are the interactions between levels i and ßj, and ijk is the error for the kth replicate of (i, ßj) ~ N (0, ).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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) was similar among treatments prior to 16 d and after 42 d. From 16 to 21 d and from 21 to 42 d, poults fed either enzyme-supplemented diets or NC had increased FI over those fed the PC diet. Live weight gain (Table 3) was similar between both control groups, with the exception of the 8- to 12-d period. During this time, birds fed the NC diet gained more than those fed the PC diet. Live weight gain was influenced by treatment within the first 12 d. From 0 to 4 d, LWG of poults consuming diets supplemented with 500 and 750 g of AZ1502/tonne gained less than those consuming the PC diet but were similar to those fed the NC and diets supplemented with 250 g of AZ1502/tonne. From 4 to 8 d, LWG was greater for birds consuming AZ1502-supplemented diets as compared with those fed the PC diet. However, the 4-to 8-d LWG increase was similar when compared with NC-fed birds. No change in FCR was observed from 0 to 21 d (Table 4). Increases in FCR were observed from 21 to 42 d in those fed the NC and enzyme-supplemented diets, compared with birds fed the PC diet. Cumulatively (0 to 56 d), there were no differences among treatments for the measured traits FI (Table 2), LWG (Table 3), or FCR (Table 4). Treatment had no effect on mortality throughout the trial (data not shown).
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) were reduced in poults fed the NC diets at d 4, 8, 16, and 42. The addition of enzyme had no effect on energy or protein through 16 d when compared with birds fed the NC diet. However, at d 42 the addition of enzyme improved energy and protein over NC-fed birds. At 42 d, supplementing diets with 250 g of AZ1502/tonne improved the energy of birds over those fed the PC diet. Significant improvements in protein were noted when 250 and 500 g of AZ1502/tonne was supplemented, as compared with poults fed the PC diet.
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) proved to be the only significant effect (P < 0.0001) with regard to intestinal measurements, with no effect of treatment (data not shown). Both duodenal and ileal villi increased in height throughout the measured period. Jejunal villi remained similar from d 4 to 8, with subsequent increases in height thereafter. The change in crypt depths over time was less pronounced in comparison with villus heights. Changes in the villus-to-crypt ratios became significant between d 16 and 21, which may suggest a crucial time in gut development.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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Zanella et al. (1999) theorized that growth improvements observed with the addition of exogenous enzymes were most likely caused by the increased digestibility of the diets. Increasing the efficiency of digestion would allow more energy to be partitioned toward growth. In the current trial, energy and protein decreased (P < 0.0001) when birds were fed the NC diet. Enzyme addition had no effect on digestibility beyond 42 d. This may be attributed to the fact that the starter 1 diet had the largest (97.0 kcal/kg) PC to NC energy drop. Digestibility may also have been affected by a dietary interaction between AZ1502 and copper sulfate (CuSO4), which was reported by Marron et al. (2001). In the present trial, CuSO4 was included at 600 ppm, and Marron et al. (2001) reported a depression in digestibility when broiler diets were supplemented with 300 ppm. Although not analyzed, the high inclusion of CuSO4 in this trial may have limited the enzyme response in terms of digestibility.
Tarachai and Yamauchi (2000) found that villus growth was not regulated by parenteral alimentation or physical stimulation of the gut. Rather, enteral absorption of nutrients stimulated an increase in villus height. If enteral absorption stimulates morphological changes in the gut, one could conclude that increasing the available substrate for absorption (through the action of an exogenous enzyme) would further increase the villus height. Ritz et al. (1995) reported similar findings in poults (0 to 21 d) fed corn-SBM diets supplemented with either amylase or xylanase. Those authors found that villus height within the jejunum and ileum was increased with amylase supplementation. Their findings were in contrast to the current study, which resulted in no influence of dietary treatment on villus height or crypt depth.
In the present trial, enzyme addition had little effect on production; however, slight improvements were noted in digestibility prior to 42 d, with significant improvement over the PC diet occurring on d 42. As feed additives become more commonplace in today’s industry, further research will be needed to focus on potential interactions among dietary components. In conclusion, the potential exists to increase digestibility of corn-SBM diets with the use of exogenous enzyme cocktails. However, for these increases to be cost effective in terms of production, a larger reduction in energy may be needed to demonstrate their complete potential.
Received for publication May 9, 2006. Accepted for publication November 11, 2006.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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