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ANIMAL NUTRITION |
Department of Animal Science, University of Manitoba, Winnipeg, Manitoba, R3T 2N2 Canada
Abstract
Two experiments with young pigs (25 d of age) were conducted to investigate the effect of multienzyme preparations on nutrient digestibility, growth performance, and P utilization and excretion. In Exp. 1, 24 pigs (six pigs per treatment) were used in a 28-d performance and digestibility trial using four diets: control (no enzyme) and control supplemented with enzyme preparation A, B, or C. The control diet was formulated to meet 95% of NRC (1998)
nutrient specifications (except for available P, which was at 44% NRC) and composed of corn, wheat, wheat by-products, barley, soybean meal, canola meal, and peas. All three enzyme preparations contained xylanase, glucanase, amylase, protease, invertase, and phytase activities and differed in the type of plant cell wall-degrading activities; Enzyme A contained cellulase, galactanase, and mannanase; Enzyme B contained cellulase and pectinase; and Enzyme C contained cellulase, galactanase, mannanase, and pectinase. Pigs fed enzyme-supplemented diets had higher ADG (P = 0.02) and G:F (P = 0.01) than those fed the control diet. On average, and when compared with control diet, enzyme supplementation improved (P = 0.001 to 0.04) ileal digestibility of DM (60 vs. 66%), GE (62.8 vs. 70.4%), CP (62 vs. 72%), starch (86.7 vs. 94.2%), nonstarch polysaccharides (NSP; 10.1 vs. 17.6%), and phytate (59 vs. 70%). Compared with the control, total-tract digestibility of nutrients was increased (P = 0.001 to 0.01) owing to enzyme supplementation, with Enzyme C showing the highest improvement in DM, GE, CP, starch, NSP, phytate, and P utilization. Pigs fed enzyme-supplemented diets had decreased (P = 0.04) fecal P excretion. The benefit from improved nutrient utilization with enzyme supplementation was further substantiated in a 38-d growth performance study with 48 pigs. The control and Enzyme C-supplemented diets (same as Exp. 1) were assigned to six replicate pens (four pigs per pen). The study was conducted in three phases (Phase 1 = d 0 to 7; Phase 2 = d 7 to 21; Phase 3 = d 21 to 38). Individual BW and pen feed disappearance were monitored. Average daily gain and G:F were 231 and 257 g (P = 0.01), and 0.56 and 0.63 (P = 0.001) for the control and enzyme-supplemented diets, respectively. It is evident from this study that the use of enzyme preparations may allow for cost-effective and environmentally friendly formulation of young pig diets.
Key Words: Early-Weaned Pigs • Multienzyme Preparations • Nutrient Digestibility
Introduction
Young pigs have a limited ability to effectively utilize diets containing lower-quality ingredients with high fiber content. It is well documented that wheat, barley, oats, rye, and their by-products contain large amounts of nonstarch polysaccharides (NSP) with antinutritional activities that may affect nutrient utilization by young pigs (Hesselman and Aman 1986; Li et al., 1996). However, with appropriate enzyme preparations, these antinutritional effects can be alleviated with a potential to improve the nutritional value of such feedstuffs for young pigs (Simons et al., 1990; Li et al., 1996). Thus far, the use of exogenous enzymes to degrade indigestible dietary components has yielded inconsistent results mainly because of the presence of complex substrates in feedstuffs and the use of enzyme activities often not suitable for effective hydrolysis of such components (Slominski, 2000). Previous research with poultry (Cleophas et al., 1995) and pigs (Graham et al., 1988) suggested that a combination of different enzyme activities is required for complete degradation of complex NSP and improved nutrient utilization. Recent in vitro studies showed that a combination of carbohydrase enzymes was more effective in NSP depolymerization of soybean meal, canola meal, and peas than when the individual carbohydrases were used (Meng et al., 2002).
Although the use of multienzyme preparations to enhance nutrient utilization has been extensively evaluated in studies with chickens, only a few studies have been conducted to determine their effects on pig performance. The few studies conducted with pigs have mainly involved growing pigs and provided inconsistent results (Officer, 1995; Li et al., 1996). The objective of the current study was to investigate the effect of multienzyme preparations on nutrient digestibility, growth performance, and P utilization and excretion of young pigs fed diets based on a wide selection of inexpensive but low-quality ingredients.
Materials and Methods
Experiment 1
Experimental Diets.
All pigs were fed a commercial starter diet for an adaptation period of 1 wk prior to the start of the experiment. The dietary treatments consisted of a control (no enzyme) and control supplemented with enzyme preparation A, B, or C. The control diet was formulated to meet 95% NRC (1998) nutrient specification (except for available phosphorus which was at 44% NRC) and composed of corn, wheat, wheat by-products, barley, soybean meal, canola meal and peas (Table 1). All three enzyme preparations provided 250 units of xylanase, 150 units of glucanase, 0.001% amylase, 0.0003% protease, 0.002% invertase, and 400 units of phytase activities per kilogram of diet and differed in the type of plant cell wall-degrading activities. Enzyme A contained cellulase, galactanase, and mannanase; Enzyme B contained cellulose and pectinase; and Enzyme C contained cellulase, galactanase, mannanase, and pectinase. The cell wall-degrading enzymes were selected based on the in vitro incubation studies conducted in our laboratory (Meng et al., 2002). Under the conditions of the assay (pH 5.2, 40°C), the three enzyme preparations showed a gradual increase in the degree of NSP depolymerization, with Enzyme C being the most effective in soybean meal, canola meal, and peas NSP hydrolysis, which averaged 19.5, 34.0, and 24.7%, respectively. Enzyme supplements were provided by Canadian Bio-Systems Inc., Calgary, Alberta, Canada. Mill run and wheat screenings were provided by Ritchie Smith Feeds, Abbotsford, BC, Canada. Chromic oxide was added as an indigestible marker and all diets were steam pelleted at 80°C.
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Twenty-four Cotswold pigs weaned at 18 ± 1 d of age and weighing 6.52 ± 0.83 (mean ± SD) kg BW were obtained from the University of Manitoba Glenlea Swine Research Farm and housed individually in pens with plastic-covered expanded metal floors. The piglets were fed a commercial diet for a 7-d adaptation period, and the average weight at the end of the adaptation period was 7.0 ± 0.42 (mean ± SD) kg. The pigs were then assigned randomly to the four dietary treatments on the basis of sex and BW. Each dietary treatment was assigned to six replicate pens (one pig per pen). Pigs had unlimited access to feed and water throughout the 4-wk study. Body weight and feed disappearance were monitored weekly. Room temperature was initially set at 29.5°C and gradually decreased by 1.5°C/wk. Fecal grab samples were collected from each pig during the last week of the experiment. At the end of the trial, all pigs were held under halothane general anesthesia and killed by an intracardiac injection of sodium pentobarbital (50 mg/kg BW). Digesta samples were collected from the ileum, and the third metatarsal bone of the left hind leg was recovered from each pig and along with digesta samples were kept frozen at -20°C until required for analysis. All experimental procedures were reviewed and approved by the University of Manitoba Animal Care Committee and pigs were cared for according to the guidelines of the Canadian Council on Animal Care (CCAC, 1993).
Sample Preparation and Chemical Analyses
All analyses were performed in duplicate. Digesta and fecal grab samples were freeze-dried and, along with diet samples, finely ground to pass through a 1-mm screen before chemical analyses. Ileal and fecal samples were analyzed for DM, starch, NSP, phytate, GE, and CP. Fecal samples were further analyzed for phosphorus according to the AOAC procedures (AOAC, 1990). Phytate content in the diet, digesta, and fecal samples was determined using the method of Haug and Lantzsch (1983). Chromic oxide was analyzed as described by Williams et al. (1962). Crude protein (N x 6.25) content was determined using a Leco NS 2000 Nitrogen Analyzer (LECO Corporation, St. Joseph, MI). Gross energy was measured using a Parr adiabatic oxygen bomb calorimeter (Parr Instrument Co., Moline, IL) that had originally been calibrated. Nonstarch polysaccharides were determined by gas-liquid chromatography (component neutral sugars) and by colorimetry (uronic acids). The procedure for measuring neutral sugars was that described by Englyst and Cummings (1984) except that the acetylation with N-methylimidazole and acetic anhydride was carried out for 30 min at 20°C as modified by Slominski and Campbell (1990). Starch was analyzed by the procedure described by Macrae and Armstrong (1968) using the glucose HK reagent kit (Sigma Chemical Co., St. Louis, MO). Bone ash was determined as described by Spencer et al. (2000) except that broken bones were wrapped in Whatman’s No. 42 filter paper and defatted in hexane for 48 h rather than 6 d. The broken bones were then air-dried and ashed in the furnace at 600°C for 12 h. Bone ash was expressed as a percentage of dry fat-free bone weight.
Experiment 2
Forty-eight Cotswold pigs averaging 6.21 ± 0.74 (mean ± SD) kg BW and weaned at 18 ± 1 d (mean ± SD) were used in a 38-d growth trial (3 phases). Phase 1 was a 7-d period, whereas Phases 2 and 3 lasted 10 and 21 d, respectively. The pigs were assigned randomly to two dietary treatments on the basis of sex and BW. Each dietary treatment was assigned to six replicate pens (four pigs per pen). The two diets were steam-pelleted at 80°C and were similar to the control and Enzyme C-supplemented diets used in Exp. 1. However, the amount of wheat was increased to replace corn and hulless barley (Table 1
), in order to determine whether the enzyme preparation could still improve growth performance in piglets fed diets with an increased concentration of antinutritional factors. The enzyme blend supplement used in this experiment was similar to Enzyme C used in Exp. 1. Experimental diets were assigned to six replicate pens each with four pigs per pen. Pigs had unlimited access to feed and water. Individual BW and pen feed disappearance were monitored weekly.
Calculations and Statistical Analysis
Digestibility coefficients were calculated using the following formula:
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where
Data from both experiments were analyzed as a completely randomized design using the General Linear Models procedures of SAS (SAS Inst. Inc., Cary, NC). When a significant F-value for treatment means (P < 0.05) was observed in the analysis of variance, treatment means were compared using Duncan’s multiple-range test (Duncan, 1955). In Exp. 2, data were analyzed using the t-test procedure.
Results and Discussion
Animal Performance (Exp. 1)
Average daily feed intake (ADFI), ADG, and G:F are shown in Table 2. There were no differences in ADFI among treatments (P = 0.42). Pigs fed enzyme-supplemented diets had a higher ADG (P = 0.02) and G:F (P = 0.01) than those fed the control diet. However, there were no differences in ADG (P = 0.06) and G:F (P = 0.13) among the enzyme-supplemented diets. The current results are in agreement with those of Baidoo et al. (1997), who reported an improvement in feed efficiency of growing pigs fed hulless barley diets supplemented with a blend of ß-glucanase, xylanase, amylase, and pectinase enzymes. Most of the studies with pigs on the use of enzymes have been done with pigs of initial weight of 19 kg and above, with different multienzyme blends. Thus, there is little or no information on the effect of supplementation of weaned (18 to 24 d) pig diets with multienzyme blends similar to those used in this study. Furthermore, in studies with growing and finishing pigs, the effects of multienzyme supplementation have been contradictory. In a study with a wheat/soybean-based diet supplemented with a multienzyme preparation (ß-glucanase, hemicellulase, pentosanase, and cellulase), Officer (1995) found no improvement in ADFI, ADG, and feed conversion efficiency of pigs weaned at 27 to 29 d. However, Grandhi (2001) found improvement in feed conversion efficiency but not in ADFI and ADG when barley diets supplemented with commercial carbohydrases (Ronozyme W) were fed to 20-kg pigs. On the contrary, Thacker et al. (1988) did not observe any significant improvement in ADFI, ADG, or feed efficiency when growing-finishing pigs (80 kg BW) were fed hulless barley diets supplemented with multienzyme preparations containing ß-glucanase, pentosanase, cellulase, amylase, and pectinase.
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). Also, the extent to which enzyme supplementation improves nutrient digestibility tends to be low when using diets containing highly digestible ingredients (Johnson et al., 1993). From a practical swine nutrition perspective, it would appear that supplementing enzymes to pig diets will be more beneficial when using diets based on ingredients that are of lower quality and poorly digested as was the case in the current study. Apparent Ileal Digestibility of Nutrients (Exp. 1)
Apparent ileal digestibilities of DM, starch, GE, CP, and phytate were similar among enzyme-supplemented diets (P = 0.17 to 0.23) and were all higher (P = 0.001 to 0.04) than those observed for the control diet (Table 3). However, NSP digestibility was further improved (P = 0.01) in pigs fed Enzyme C-supplemented diet compared with Enzyme A or B. In a study with 8- to 12-wk-old piglets fed soybean/rapeseed meal-based diet, supplementation with 
-amylase or a multienzyme preparation containing -galactosidase, xylanase, and protease was shown to improve ileal digestibility of DM but not that of starch, total NSP, and CP (Gdala et al., 1997). Li et al. (1996) reported improved ileal digestibilities of DM, CP, and GE in 28-d-old piglets fed hulless barley or wheat/soybean meal diets supplemented with 0.2% ß-glucanase (a mixture of enzymes with endo- and exo-ß-glucanase and ß-glucosidase activities). Similarly, it was reported that broiler chickens fed a wheat/hulless barley/canola meal-based diet supplemented with multienzyme preparations (xylanase, ß-glucanase, and a broad spectrum of other enzyme activities) had increased (P < 0.05) DM, starch, NSP, and phytate digestibilities compared with the unsupplemented diet (Slominski, 2000). In pigs fed the enzyme-supplemented diets, average DM and starch digestibility values obtained in the present study (66.2 and 94.2%) are close to those (67.8 and 98.1%) reported by Slominski (2000) for young pigs.
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, in which young pigs were fed a corn/soybean meal-based diet with microbial phytase plus organic acids supplementation. However, the current values for ileal phytate digestibility were higher than those reported by Li (2000) in young pigs fed wheat-hulless barley-based diets supplemented with microbial phytase and carbohydrase enzymes.
The observed differences among studies for the ileal digestibility of nutrients (especially, starch, GE, NSP, and crude protein) may be due to variability in the age of pigs used in different experiments. Graham et al. (1988) suggested that in pigs, fiber-degrading capacity in the small intestine increases with age. Multienzyme supplementation may therefore be more beneficial in diets for early-weaned rather than for growing or finishing pigs. Differences in response to multienzyme supplementation among studies may also depend on dietary NSP composition and content. The mixed linked ß-glucans of barley are mainly localized in the cell walls of the endosperm and the hull, and represent about 75% of the polysaccharides in barley, the remainder being mainly cellulose, arabinoxylans, mannose containing polymers, protein, and phenolic compounds (Fincher, 1975; de Silva et al., 1983). Similarly, in wheat the noncellulosic polysaccharides consist mainly of arabinoxylans and ß-glucans, whereas in soybean, canola, or peas arabinogalactans, arabinans, galactans, galactomannans, mannans, and pectic polysaccharides predominate (Slominski, 2000).
In cereal grains, arabinoxylans and ß-glucans are found in the cell walls of the protein-rich aleurone layer and starchy endosperm (Basic and Stone, 1991) and can act as a physical hindrance to nutrient hydrolysis and absorption. Similarly, the cell wall polysaccharides of soybean, canola seed, or peas may also be responsible for the nutrient-encapsulating effect. In this case, starch and intracellular protein may be surrounded by cell wall structure and thus unavailable for digestion in the ileum, as was seen in the present study in pigs fed the control diet. However, with the addition of carbohydrase enzymes containing a wide range of cell wall-degrading activities, the cell wall polysaccharides could be broken down and the cell walls, at least partly, depolymerized (Fleming and Kawakami, 1977; Hesselman and Aman, 1985; Meng et al., 2002). This may have led to the improved utilization of nutrients observed in the current study. This may also be attributed to the breakdown of potential linkages that existed between phytate molecules, proteins, and starch considering that the multienzyme preparations used in the present study contained the phytase activity.
Gross energy digestibility values determined in the current study were significantly higher (P = 0.001) in enzyme-supplemented diets relative to the control, and the results were similar to values reported by Li et al. (1996) in a trial where a mixture of carbohydrase enzymes was added to a hulless barley/wheat-based diet and fed to 28-d-old piglets. Similarly, Graham et al. (1986) and Jensen et al. (1998) observed a consistent increase in starch and GE digestibility following ß-glucanase supplementation. The increase in GE digestibility in the present study due to enzyme supplementation is consistent with the improved ileal starch digestibility. It is well known that the absorption of starch as glucose in the small intestine is more effective in terms of energy utilization than its conversion to short-chain fatty acids and their absorption in the large intestine (NRC, 1998). Therefore, the increase in starch digestibility in the ileum will represent an increase in ileal glucose uptake and a subsequent increase in energy utilization.
Total-Tract Digestibility of Nutrients (Exp. 1)
Total-tract nutrient digestibilities are shown in Table 4. Compared with control, enzyme supplementation increased (P = 0.001 to 0.014) total-tract digestibilities of DM, starch, NSP, GE, CP, and phytate. Although starch utilization was almost complete for the control diet, enzyme supplementation further increased (P = 0.006) its fecal digestibility. Graham et al. (1989) and Slominski (2000) reported that in pigs starch is almost completely digested when determined at the fecal level irrespective of dietary treatments as the microorganisms in the large intestine can effectively ferment complex polysaccharides. This was clearly the case in the present study, where NSP digestibility was higher at the fecal than in the ileal level, irrespective of dietary treatment. The piglets fed enzyme-supplemented diets had higher (P = 0.001) fecal NSP digestibilities than those fed the control diet (Table 4). Furthermore, fecal NSP digestibility increased by 6.4-percentage units when pigs were fed Enzyme C compared to Enzyme A and B (66.8% vs. 61.2 and 59.6%, respectively). This unit increase is in agreement with that of Slominski (2000), who reported a 5.9-percentage unit increase when NSP digestibility values for enzyme-supplemented diets was compared to a non-enzyme-supplemented diet.
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who found an increase of 2.6 and 5.4 percentage units in gross energy and crude protein digestibilities, when a hulless barley/soybean meal diet supplemented with 0.2% ß-glucanase (endo- and exo-ß-glucanase, and ß-glucosidase activities) was fed to young pigs. Conversely, Thacker et al. (1992) in studies with 7- to 8-wk-old pigs, reported no effect of ß-glucanase supplementation on the fecal digestibilities of CP and GE.
The improvements in fecal crude protein and phytate digestibilities observed in the current study may have significant environmental implications as reduced amount of nitrogen and phosphorus would be excreted into the environment following dietary enzyme supplementation. In a study with chickens, Jacob et al. (2000) observed increased fecal nitrogen digestibility in 5-wk-old broilers fed diets supplemented with a wide range of enzyme activities, which was associated with a 12.2% reduction in daily nitrogen output.
Utilization of Phosphorus (Exp. 1)
Total-tract phosphorus digestibility and fecal phosphorus excretion, and bone ash content are illustrated in Figures 1 and 2, respectively. Pigs fed enzyme-supplemented diets had higher total-tract phosphorus digestibilities (P = 0.001), and excreted lower amounts of phosphorus (P = 0.04) than those fed the control diet. There were no differences in any of these response criteria among the enzyme-supplemented diets (P = 0.23). Enzyme supplementation had a nonsignificant (P = 0.07) but positive effect to improve bone ash content (Figure 2).
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and Harper et al. (1997) reported only a 44% and 33% improvement, respectively, in total-tract phosphorus digestibilities when 500 U/kg dietary phytase was added to a sorghum-soybean meal-based diet fed to growing pigs. In addition, there was an improvement (P = 0.07) of approximately 5.1% in the bone ash content in the current study in pigs fed enzyme-supplemented diets. It could be argued that the additional phosphate liberated due to improved phytate hydrolysis in enzyme-supplemented diets was utilized for bone development. There was a 25.3% decrease (P = 0.04) in fecal P output (kilograms per metric ton of dry feces) for pigs fed Enzyme A, B, or C supplemented diets compared with the control. This was higher than the value (20%) observed in our earlier study, Omogbenigun et al. (2003), in which only microbial phytase and organic acids were used. Nonetheless, the extent to which fecal phosphorus output was reduced in the present study and that of our earlier study is in close agreement with the values reported by Lei et al. (1993) and Harper et al. (1997), who reported 21.5 to 35% decrease in phosphorus excretion with 500 phytase units/kg of diet fed to young pigs. The basal diet used in the current study was formulated with a range of feedstuffs that are known to be poorly digested by young pigs. Supplementation of this diet with different enzyme cocktails improved the digestibility of all dietary nutrients examined, indicating a potential for the simultaneous use of lower quality feed ingredients and appropriate enzyme combinations in diets for young pigs.
Animal Performance (Exp. 2)
Average daily feed intake, ADG, and G:F are shown in Table 5. In Phase 1, there were no differences in ADFI (P = 0.24) between the pigs fed the control and enzyme-supplemented diets. However, pigs fed the enzyme-supplemented diet had a higher ADG (P = 0.04) and gain:feed (P = 0.001) than those fed the control diet. In Phase 2, ADFI followed the same trend as in Phase 1 with no significant difference (P = 0.18) between the pigs fed enzyme-supplemented diet and those fed the control diet. However, pigs fed enzyme-supplemented diet had a higher ADG (P = 0.001) and G:F (P = 0.04) than those fed the control diet. Similarly, values observed in Phase 3 and overall followed the trend observed in phase 2. Pigs fed the enzyme-supplemented diet had a significantly better ADG (P = 0.0001) and G:F ratio (P = 0.0001) than those fed the unsupplemented diet.
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, who reported an improvement in feed efficiency in growing pigs fed hulless barley diets supplemented with a mixture of ß-glucanase, xylanase, amylase, and pectinase. Meng et al. (2002) observed that a multienzyme preparation containing xylanase, glucanase, cellulase, pectinase, galactanase, mannanase, and phytase activities were able to break down many dietary fiber constituents, which in the current study represented the major antinutritional factors present in the diets. In conclusion, the growth data obtained in both experiments suggest that the multienzyme preparation improved growth performance by enhancing nutrient utilization in a pig starter diet based on lower quality ingredients. This is important from the practical pork production standpoint and suggests that ingredients known to be poorly digested by early-weaned pigs can be utilized in starter diets with adequate enzyme supplementation. Implications
The results of the current study clearly demonstrate that, with an appropriate enzyme combination, young pigs can effectively utilize diets containing ingredients that are normally poorly utilized. This will increase the flexibility in feed formulation allowing for the use of lower-quality ingredients, with the potential to reduce feed costs. Application of multienzyme preparations would also have tremendous advantage in minimizing nitrogen and phosphorus excretion into the environment.
Footnotes
1 This research was financially supported by the Agri-Food Research Development Initiative (ARDI), Canadian Bio-Systems Inc., and the Manitoba Pork Council. The help of R. Stuski with animal care, K. Carrette and T. Davie with technical assistance, and G. H. Crow with statistical design are gratefully acknowledged. 
2 Presented in part at the 9th International Symp. Digest. Physiol. Pig, Banff, Alberta, May 14–17, 2003.
3 Correspondence—phone: 204-474-7323; fax: 204-474-7628;e-mail: martin_nyachoti{at}umanitoba.ca.
Received for publication June 25, 2003. Accepted for publication January 9, 2004.
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