J. Anim. Sci. 2004. 82:2647-2656
© 2004 American Society of Animal Science
Effect of supplementation of xylanase and phospholipase to a wheat-based diet for weanling pigs on nutrient digestibility and concentrations of microbial metabolites in ileal digesta and feces1
G. Diebold*,2,
R. Mosenthin*,3,
H.-P. Piepho
and
W. C. Sauer
* Institute of Animal Nutrition and
and
Bioinformatics Unit, University of Hohenheim, 70599 Stuttgart, Germany, and
and
Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada
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Abstract
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The objective of this study was to determine the effect of supplementing a wheat-based diet with xylanase and phospholipase either alone or in combination on the ileal and fecal digestibilities of nutrients and energy in early-weaned pigs. In addition, the concentrations of ammonia, lactate, and VFA were measured in ileal digesta and feces. The experiment was carried out with 16 barrows weaned at the age of 11 d with an average initial BW of 4.1 kg. On d 4 and 5 postweaning, the piglets were fitted with a simple T-cannula at the distal ileum. The experiment was designed as a balanced incomplete block design with three periods. The piglets received the basal diet with or without supplementation of either xylanase or phospholipase or a combination of these. There was a positive (P = 0.005 to 0.018) effect on the digestibility values of GE, OM, CP, crude fiber (CF), and NDF with xylanase supplementation. Apart from lysine, threonine, cysteine, glycine, and proline, the digestibility values of all AA were improved (P = 0.001 to 0.024). Phospholipase supplementation had a positive effect on CP (P = 0.047) and CF (P = 0.002) digestibilities, but no effect on ether extract (EE) digestibility. Supplementation of both enzymes showed the largest response in nutrient digestibilities, except that EE digestibility was not affected. No differences were found in D-/L- lactate, and ammonia concentrations among treatments. Acetate and propionate concentrations tended to increase when xylanase was supplemented and were highest for the combination of both enzymes. Despite the positive effects on ileal nutrient and energy digestibilities, there was no effect of xylanase or the combined enzyme supplementation on the fecal digestibilities of OM, CP, EE, CF, NDF, ADF, or GE, and on fecal concentrations of VFA. Phospholipase alone slightly decreased the total-tract nutrient and energy digestibilities (P < 0.05). In conclusion, the combination of both enzymes generally led to the highest increases in ileal digestibilities, which were of small numerical magnitude (approximately 2%). However, on a relative basis, this increase of 2% represents approximately 13% of the remaining diet that was available for digestion based on the fact that approximately 15% of the diet was not digested in the control pigs. Thus, the potential benefits in the nutrition of weanling pigs from combinations of enzymes should be validated under practical conditions.
Key Words: Digestibility • Enzyme • Piglet • Phospholipase • Supplementation • Xylanase
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Introduction
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The cell walls of cereals contain up to 15% nonstarch polysaccharides (NSP); exogenous enzymes can hydrolyze these carbohydrates into smaller units that can be utilized by the pig. As summarized by Partridge and Bedford (2000)
, pigs receiving enzyme-supplemented diets usually fail to show the same consistent improvements in nutrient digestibilities and growth performance as observed in poultry (except phytase for improving P digestibility). Recent studies have focused on the effects of enzyme supplementation to diets for weanling pigs. In young pigs, poor nutrient utilization has been attributed, in part, to the immaturity of the digestive system including hydrolysis of NSP. Significant improvements in growth performance were observed when xylanase was supplemented to wheat-based diets (Dusel et al., 1997; Jeroch et al., 1999); however, these studies were not always accompanied by digestibility studies, in particular those with a focus on ileal digestibilities.
In addition to NSP-hydrolyzing enzymes, lipases are also supplemented to poultry diets to improve fat digestibility (Tan et al., 2000). Although exogenous lipases are sometimes included in swine diets as part of multi-enzyme products, they may be at concentrations so low that a possible positive effect on fat digestibility cannot be detected. According to Cera et al. (1988), the digestibility of fat at weaning declines from over 90% (sows milk) to 65 to 80% (tallow and corn oil, respectively). Supplementation of lipase may overcome the decrease in fat digestibility. This becomes even more important since both gastric and pancreatic lipase activities are relatively low up to 14 d of age (Liu et al., 2001).
The objective of this study was to determine the effect of supplementation of a wheat-based diet with xylanase and phospholipase alone and in combination on the ileal and fecal digestibilities of nutrients and energy as well as on measures of microbial metabolism in weanling pigs.
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Materials and Methods
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Animals and Housing
This experiment was carried out with 16 barrows (German Landrace x Piétrain) with an average initial BW of 4.1 kg that were weaned when 11 d old. The piglets were obtained from a production herd (Research Station Unterer Lindenhof, Hohenheim University, Stuttgart, Germany). The piglets were housed individually and able to freely move around in the crates (1 m x 1 m), which allowed for visual contact with each other. The temperature in the barn was 30°C at the beginning of the experiment and was slowly decreased to 25°C on d 8 and then kept constant until the end of the trial. The humidity ranged between 60 and 70%. Each crate was equipped with an infrared heating lamp and a low-pressure drinking nipple, which allowed free access to water. To ease the transition of the piglets to the crates, they were kept in pairs for the first 2 d. Before and after surgery until d 8 postweaning, the piglets were fed ad libitum a commercial milk replacer (Milkivit, Burgheim, Germany) five times daily at 0800, 1200, 1600, 2000, and 2400.
Surgical Procedures
On d 4 and 5 postweaning, the piglets were fitted with a simple T-cannula at the distal ileum, as was described by Li et al. (1993). The cannulas were prepared from a plastisol solution (Techniplast CA-1098 clear, FH & Sons Mfg., Ltd., Rexdale, ON, Canada), according to procedures adapted from Li (1992). The internal diameter of the barrel of the cannula was 10 mm and the length was 70 mm; the wings were 12 mm wide and 35 mm long. The washer had a diameter of 45 mm and a 20-mm-long short barrel. Natural rubber plugs (Rotilabo, No. C378.1, Carl Roth GmbH, Karlsruhe, Germany) were used as stoppers. The research protocol was approved by the German Ethical Commission for Animal Welfare. Care of the animals used in this experiment was in accordance with the guidelines issued by German regulation for care and treatments of animals (Lorz and Metzger, 1999).
Experimental Design and Dietary Treatments
The experiment was designed as a balanced incomplete block design with three periods. Within each experimental period, four different diets were fed to three or four pigs each (Table 1). The piglets received the basal diet with or without supplementation with xylanase, phospholipase, or a combination of these. The level of enzyme supplementation was based on recommendations by the manufacturer (BASF AG, Ludwigshafen, Germany): xylanase (endo-1,4-ß-xylanase; EC 3.2.1.8) and phospholipase (phospholipase A2; EC 3.1.1.4) were added at levels of 5,600 EXU/kg and 1,000 IU/kg diet, respectively. One EXU (endo-xylanase unit) is defined as the amount of enzyme required to liberate 4.53 µmol/min of reducing sugars (measured as xylose equivalents) from a 0.5% arabinoxylan solution at pH 3.5 and 40°C (Engelen et al., 1996). One IU of phospholipase activity is defined as the amount of enzyme producing 1 µmol/min of FFA under standard conditions (egg yolk substrate, 0.4% phospholipids, pH 8, 40°C, 6 mM Ca2+) as described by Beudeker and Kies (2000). The enzyme product was added to the diet by using a portion of the basal diet (2.5 kg/100 kg of entire diet) as carrier.
In addition to the milk replacer, limited amounts of the experimental diets were available to the piglets the day after surgery. Starting on d 9 postweaning, the piglets were only fed the experimental diets according to the experimental design.
The basal diet contained wheat, wheat bran, soybeans, soy protein isolate and tallow, sucrose, and skim milk powder to possibly stimulate feed intake (Table 2). The diets were supplied as mash to avoid heat damage to the enzymes that may have occurred if they had been provided as pellets. All components were ground to pass a 2-mm mesh screen, except wheat bran, which was ground to pass a 1-mm mesh screen to possibly improve the flow of digesta through the barrel of the cannula and thus to enhance the likelihood of obtaining representative samples of digesta. Nutrients and energy were supplied according to NRC (1998) standards for piglets from 5 to 10 kg (Table 3). Titanium oxide (TiO2, 0.2%) was used as digestibility marker.
Experimental Procedures
After a 3-d recuperation period from surgery, the pigs were fed twice daily (0800 and 2000). The pigs were allowed to consume the experimental diets at a maximum rate of 7% of the individual BW determined 12 h before the initiation of each experimental period. The collection of feces, by aid of colostomy bags (Combihesive Natura, ConvaTec Ltd., Uxbridge, U.K.) attached to the anus, was initiated at 0800 on d 7 of each experimental period and continued for 72 consecutive hours. The bags were changed each time feces were voided. After taking adequate samples for VFA analyses, all samples were frozen and stored at –20°C.
Ileal digesta were collected for a total of 48 h beginning at d 10 in four 12-h periods with 6-h intervals: 0800 to 2000, 0200 to 1400, 2000 to 0800, and 1400 to 0200. The collection procedure was adapted from Li et al. (1993) using plastic tubing attached to the barrel of the cannula by elastic bands. They were changed every 20 min. During the first 12 h of collection, digesta were stored at 2°C and pooled for each animal. Adequate samples for analyses of lactate, ammonia, pH, and VFA were taken from these samples and stored at –20°C. During the following collection periods, 2 mL of 2.5 M formic acid was added to the sampling bags in order to minimize further bacterial fermentation in digesta. Each experimental period comprised 13 d.
Samples of digesta and feces were pooled within each animal and period, freeze-dried and ground in an oscillating-disk-mill (Siebtechnik GmbH, Muehlheim-Ruhr, Germany) to a particle size of less than 0.4 mm. This grinding procedure, which was also used to grind the diet samples, is of special benefit as it produces a very homogenous material without heat damage to the samples.
Feed intake was recorded daily. Weight gain was measured at the beginning of each period and at the conclusion of the trial.
Analytical Procedures
Determination of DM, OM, CP, ether extract (EE), and crude fiber (CF) were performed as outlined by Naumann et al. (1976). Acid detergent fiber and NDF were determined according to Goering and van Soest (1972). The energy contents of digesta, feces, and diets were analyzed using an adiabatic bomb calorimeter (IKA calorimeter, C4000, IKA-Analysentechnik, Heitersheim, Germany). The TiO2 content of the samples was measured using an atomic absorption spectrometer (SpectrAA 220 FS, Varian, Darmstadt, Germany) according to principles described by Brandt and Allam (1987), modified by Zacharias et al. (2000). Amino acid analyses were performed as outlined by Naumann et al. (1976) (amino acid analyzer LC 3000, Eppendorf Biotronic, Hamburg, Germany). Amino acid concentrations were not corrected for incomplete recovery resulting from hydrolysis. Ammonia concentration was determined with the aid of a gas-sensitive electrode, combined with a digital voltmeter (Mettler-Toledo): 1 g of sample was diluted (1:10) with distilled water, homogenized, and centrifuged for 20 min (4,750 x g). The supernatant fluid was mixed with 0.25 mL of 10 M NaOH. The ammonia released was measured as different voltage in mV.
For analysis of D- and L-lactic acid, a commercially available photometric test kit (Boehringer, No. 1 112 821) was used. Volatile fatty acid concentrations were measured by gas chromatography (HP 6890 Plus GC-System) using 4-methyl-iso-valerianic acid as the internal standard. Samples were prepared along the principles described by Zijlstra et al. (1977) for feces.
Digestibility of nutrients and energy was calculated using TiO2 as the indicator according to the following equation:
Statistical Analyses
Data were analyzed by ANOVA using the statistical program of SAS version 8 (SAS Inst., Inc., Cary, NC). The model used was as follows:
where Yij = dependent variable for animal i within period, µ = the overall mean, 
j = deviation of animals within period and treatment, ßj = effect of period, 
1 = xylanase, 2 = phospholipase, and 
ij = residuals.
To account for between-animal variation within periods, the MIXED procedure of SAS was used, as adapted from Littell et al. (1998). This model permitted modeling of the covariance structure of the data and allowed for calculations with different variations for periods (Littell et al., 1996). Animal effects are supposed to be random. Mean differences between periods were calculated using the GLM procedure. An alpha level of 0.05 was used for determination of statistical significance and of 0.10 for the determination of statistical tendencies.
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Results
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The pigs recovered well from surgery and remained healthy throughout the experiment. One piglet lost its cannula during the last period and was killed. For this piglet, missing values were calculated for this period. The average BW was 4.5 kg ± 0.6 at the beginning of Period I and 12.6 kg ± 1.1 at the conclusion of the experiment. The average feed intake increased from about 5% of BW in Period I to the maximum allowable feed intake of 7% in Period III. There was no effect (P > 0.10) of enzyme treatment on feed intake. There were neither significant period x treatment interactions nor between-enzyme interactions for any of the variables reported throughout the paper.
Ileal Digestibility of Nutrients and Energy
There was a positive effect on the ileal digestibility values of OM, CP, CF, NDF, and energy upon xylanase supplementation (Table 4). Apart from lysine, threonine, cysteine, glycine, and proline, the digestibility values of all AA were improved. The digestibility values of lysine, cysteine, and glycine tended (P = 0.077, 0.062, and 0.057, respectively) to be higher as well. Phospholipase supplementation had a positive effect on CP and CF digestibilities and tended to increase NDF digestibility. Although CP digestibility increased by 1.2% units, CF digestibility increased by 5.9% units. However, taking into account the low digestibility values for CF the relative response in CP digestibility is actually higher in relation to the remaining undigested material. However, there was no effect on EE digestibility. The benefit of phospholipase supplementation on AA digestibility was only significant for arginine and methionine.
Supplementation of both enzymes provided the largest improvement in nutrient digestibilities, except that EE digestibility was not affected. The effects were higher in magnitude and most of these were highly significant. Crude fiber digestibility improved the most; the supplementation of both enzymes increased the digestibility value from 16.7 to 24.0%.
Concentrations of D- and L-Lactate, Volatile Fatty Acids, Ammonia, and pH in Ileal Digesta
There were no differences in ileal D- and L-lactate concentrations between treatments (Table 5). For all treatments, there were relatively low concentrations of D-lactate in ileal digesta ranging from 3.7 to 6.0 g/kg of DM; L-lactate concentrations ranged from 28.7 to 34.1 g/kg of DM. The concentrations of ammonia were approximately 100 mmol/kg of DM.
There were, however, significant differences in the concentrations of the VFA between treatments. Acetate and propionate concentrations tended to be higher in the xylanase-treated group and were 162.8 and 58.2 mmol/kg of DM, respectively. The highest concentrations, however, were observed when both enzymes were supplemented. The total VFA concentration in the xylanase-supplemented group only tended (P = 0.077) to be higher than in the control group. Butyrate concentrations were lowest and were not affected by enzyme supplementation. The pH values of ileal digesta (approximately 7) were also not affected by enzyme supplementation.
Fecal Digestibility of Nutrients and Energy, and Microbial Metabolite Concentrations in Feces
There was no effect of xylanase or the combined enzyme supplementation on the digestibilities of OM, CP, EE, CF, NDF, ADF, or GE (Table 6). In addition, there was no effect on AA digestibility values; however, phospholipase alone decreased the total-tract digestibilities of OM, CP, and GE, as well as most of the AA, by 0.8% on average. The average fecal concentrations of VFA were nearly twice the values in ileal digesta (Table 7). Xylanase tended (P = 0.058) to lower the total VFA concentration in feces.
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Table 6. The total-tract nutrient and energy digestibilities (%) of weanling pigs in response to dietary enzymesa
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Effect of Period on Nutrient and Energy Digestibilities
There were significant period effects on both ileal and fecal nutrient and energy digestibilities (Table 8). The ileal digestibility values of the parameters measured increased by approximately 5% units from Period I to II. There were no further increases in digestibility values from Period II to III with the exception of CF and NDF. The CF digestibilities increased from 12.9 to 21.6 to 29.4% from Period I to Period II to Period III, respectively; in the same order as the periods, the NDF digestibilities increased from 46.4 to 50.1 to 53.8%.
The fecal digestibilities of most nutrients also increased from Period I to II (Table 9). Except for EE and CF, the digestibilities increased again from Period II to III. The average fecal digestibilities were 5 to 10% units higher in Period III compared with Period I.
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Discussion
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As was discussed by Simon (1998), NSP-hydrolyzing enzymes may have several modes of action: partial hydrolysis of soluble and insoluble NSP, decrease in digesta viscosity, and rupturing of NSP-containing cell walls, thereby making the contents available for digestion. Other effects include shifts in the population and activities of the microflora as a result of enzyme supplementation (Vahjen et al., 1998; Simon et al., 2002). Enzyme supplementation to diets for poultry has usually shown more beneficial effects than supplementation to diets for pigs. Bedford and Classen (1992) stated that the viscosity of digesta in pigs is considerably lower than in poultry because of its higher water content; therefore, there is less opportunity to reduce the viscosity of digesta.
Supplementation of xylanase increased the apparent ileal digestibilities of OM, CF, NDF, CP, and AA, with the exception of lysine, threonine, cysteine, proline, and glycine. This study is unique in so far that surgically-modified piglets at a very early stage after weaning were used. Yin et al. (2000) also reported increases in the digestibilities of some nutrients when xylanase was supplemented to a wheat-based diet in studies with grower pigs. It has to be mentioned that xylanase supplementation can only be effective if sufficient amounts of the target substrate are available. In the present study wheat contained arabinoxylans at a level of 54 g/kg of DM.
The digestibility values of the AA, relative to each other, are in agreement with studies with piglets fed a wheat-based diet reported by Li et al. (1996). For all dietary treatments, compared with the other AA, the ileal digestibility values of arginine, methionine, and glutamic acid were relatively high, whereas those of threonine and glycine were relatively low (Table 4
). This variation among AA is in agreement with studies on growing pigs fed cereal-based diets (Sauer et al., 1991; Mosenthin et al., 1994).
The response to phospholipase supplementation was less than to xylanase. There was no effect on the ileal digestibility value of EE. Tallow was used as fat source in the diet because it was recognized that fats produced from animals, like tallow or lard, usually show lower digestibilities than vegetable fats. Cera et al. (1988) included three different fat sources (corn oil, lard, and tallow) at a level of 8% to the diets of pigs weaned at 21 d of age, and measured total tract apparent fat digestibility over a period of 4 wk after weaning. Apparent digestibility of all fat sources increased (P < 0.01) from week to week, but seemed to reach a plateau after 3 wk after weaning. In the present study, there was no further increase in fat digestibility comparing Period II with Period III. Therefore, it can be assumed that endogenous lipase was only a limiting factor during the first experimental period because of the growing ability of the pigs to effectively emulsify, digest, or absorb fatty acids with age (Cera et al., 1988, 1990). However, due to the rather large between-animal variation within periods, possible beneficial effects on fat digestibility in Period I could not be established.
In a study with broiler chicks, Al Marzooqi and Leeson (2000) reported increased ME values when lipases were added. Despite the increased ME values, feed intake and BW gain were reduced (P < 0.01). According to Carrière et al. (1998), the enzymatic activities of lipases are not always limited to one substrate. Some lipases have the ability to hydrolyze not only triglycerides but also phospho- and other lipids. Nevertheless, no reports have been published in the literature that suggest a direct mode of action of lipases on fiber. Thus, it can only be speculated if the effect on fiber digestibility is related to changes in the absorption of nutrients and/or shifts in the microbial populations, as observed for xylanase (Simon et al., 2002), or side activities of the enzyme product itself (Tan et al., 2000).
Because the supplementation with both enzymes produced the highest improvements in ileal nutrient and energy digestibility values (Table 4), it can be concluded that the positive effects of these enzymes are additive. The summed effects of xylanase and phospholipase compared to the control reflect more or less the results obtained for the enzyme combination.
The microbial population in the small intestine of pigs is dominated by aerobic and facultative anaerobic bacteria, of which lactobacilli and streptococci predominate (Dierick and Decuypere, 1996). Increasing concentrations of lactate in ileal digesta should reflect an increased population and activity of these microbes. The ileal concentrations of D- and L-lactate did not differ among treatments (Table 5). Therefore, an effect of enzyme supplementation on the populations (activities) of lactobacilli and streptococci could not be detected. From measurements of VFA concentrations in ileal digesta, it was suggested that monomers released from NSP stimulate VFA fermentation in the small intestine (Schutte, 1991; Inborr et al., 1994; Graham and Balnave, 1995). It should be noted that the monomers arabinose and xylose that are released by xylanases, are of little direct value for the animal since these pentose sugars are poorly metabolized by the pig (Yule and Fuller, 1992). In these studies, xylanase tended to increase the ileal concentrations of acetate, propionate, and total VFA. There was no effect of phospholipase supplementation alone. It should be stressed, however, that the supplementation of both enzymes resulted in the highest increases in the acetate, propionate, and total VFA concentrations in ileal digesta. Although an enhancing effect might also be assumed for phospholipase, this effect was not significant in this study. Nonetheless, the observations agree with the results of Yin et al. (2000), who also reported a numeric, but nonsignificant increase of 16% higher ileal concentrations of total VFA after xylanase supplementation to wheat-based diets. Propionate and butyrate concentrations were lower than of acetate. The values for the concentrations of the VFA were in the range of values reported by Gabert et al. (1995).
In contrast to measurements in ileal digesta, there was no effect of xylanase or the combined enzyme supplementation on total-tract digestibility values (Table 6) or on fecal concentrations of VFA (Table 7). Dierick and Decuypere (1996) stated that measurements in ileal digesta are more sensitive than those in feces for detecting the possible effects of enzyme supplementation. As was discussed by Li et al. (1993) and Mosenthin et al. (1994), differences in digestibility at the ileal level may be absent at the total tract level due to various catabolic and anabolic activities of the microflora in the large intestine. Mellange et al. (1992) reported improvements (P < 0.05) in performance after enzyme supplementation without observing an effect on the fecal digestibility values of nutrients and energy. Phospholipase alone significantly decreased the total-tract digestibility of nutrients and energy. Given that the concentration of VFA also tended to be less in the phospholipase supplemented diet the lower digestibility might be explained by a decrease in microbial activity. However, the pathways that could lead to a suppressed microbial activity in the large intestine need further investigation.
There were differences in the digestibility values of the parameters measured between the experimental periods (Tables 8 and 9). The ileal digestibility values of all nutrients increased from Period I to II. Except for CF and NDF, there were no increases in the parameters measured between Period II and III. The differences between Period I and II might be explained by the relative immaturity of the digestive tract of the early-weaned pig (Partridge and Gill, 1993). These authors associate early weaning with inadequate levels of secretion of digestive enzymes, decreased capacity of absorption due to changes in villi structure, inadequate secretion of gastric HCl, and dietary factors that cause antigenic responses in the digestive tract of the piglet. The influence of piglet age and weaning on endogenous enzyme activities was investigated by Jensen et al. (1997). At weaning (d 28), the activities of trypsin, chymotrypsin, and amylase, as well as lipase, were less than half the values when the piglets were 56 d old. Because the piglets used in the present study were weaned when they were 11 d old and fed a solid diet from d 20, it can be postulated that the enzyme activity was limiting at the initiation of the experiment. The rapidly maturing gastrointestinal tract seems to be able to adapt very fast to the challenges at weaning and there were no further improvements in nutrient digestibility values between Periods II and III. Similar to the increases in apparent ileal digestibility, fecal digestibility values (Table 9) increased significantly from Period I to II and also from Period II to III, but to a smaller extent (except for CP and EE). This might be explained, in part, by the growing microbial population in the large intestine. According to Graham et al. (1986), older pigs have a more mature gastrointestinal system and are able to better digest cereal components of the diet through the effects of both enzyme secretion and bacterial fermentation. Consequently, as the pig ages, the potential for responses to enzyme supplementation decreases.
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Implications
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The supplementation of xylanase to wheat-based diets for early-weaned pigs increases nutrient and energy digestibilities. In the present study, phospholipase supplementation showed no effect on ileal ether extract digestibility but did increase the digestibility values of some other nutrients, although to a smaller extent than xylanase. In contrast, the total-tract digestibilities of most nutrients and energy were lower after phospholipase supplementation. The combination of both enzymes produced the highest increases in nutrient and energy digestibilities. Due to associative effects, the combination of enzymes had advantages over the supplementation of a single enzyme to the diet. The effect on piglet production, however, needs to be validated in performance studies conducted under practical conditions.
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Footnotes
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1 We are very grateful to H. Brehm, T. Schlegel, and M. Steffl for their excellent work with animal surgery, to G. LaiDinh for the analyses of amino acids, and S. Roth for ammonia analyses. Financial support by BASF AG, Ludwigshafen, Germany is gratefully acknowledged. 
2 Present address: BASF Aktiengesellschaft, D-67056 Ludwigshafen, Germany.
3 Correspondence: Emil-Wolff-Str. 10 (phone: +49-711-459-3938; fax: +49-711-459-2421; e-mail: rhmosent{at}uni-hohenheim.de).
Received for publication March 28, 2003.
Accepted for publication May 25, 2004.
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O. A. Olukosi, J. S. Sands, and O. Adeola
Supplementation of carbohydrases or phytase individually or in combination to diets for weanling and growing-finishing pigs
J Anim Sci,
July 1, 2007;
85(7):
1702 - 1711.
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Abstract
Introduction
