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Poult Sci 2009. 88:316-322. doi:10.3382/ps.2008-00231
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METABOLISM AND NUTRITION

Improved energy-utilizing efficiency by enzyme preparation supplement in broiler diets with different metabolizable energy levels

Y. Zhou*, Z. Jiang*,1, D. Lv{dagger} and T. Wang*,1

* College of Animal Science & Technology, Nanjing Agricultural University, Nanjing 210095, China; and {dagger} Guangdong VTR Bio-Tech Co. Ltd., Zhuhai 519060, China

1 Corresponding author: tianwang{at}njau.edu.cn


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
A 5 x 2 x 3 factorial experiment was used to investigate the effects of 5 ME levels (12.55, 12.30, 12.05, 11.80, and 11.55 MJ/kg) supplemented with or without exogenous enzymes in diets of broilers on the nutrient digestibility and energy improving efficiency over the starter, grower, and finisher phases of growth. The results indicated that the apparent digestibility of DM decreased linearly with a reduction in the ME level in diets for the starter (R2 = 0.234, P < 0.001) and grower (R2 = 0.362, P < 0.001) phases, and increased with enzyme supplementation for all diets. The greatest improvement occurred in the diet with the lowest ME level. The AME value also decreased linearly with the reduction of ME level in diets (R2 = 0.418, P < 0.001 for starter; R2 = 0.398, P < 0.001 for grower; R2 = 0.097, P = 0.027 for finisher). Enzyme supplementation enhanced the AME value of diets in the starter, grower, and finisher phases by 0.07 ~ 0.62, 0.15 ~ 0.56, and 0.12 ~ 0.43 MJ/kg, respectively, and the optimal improvement of AME value occurred when the ME of diet was 11.55 MJ/kg in the starter phase. The effects of enzyme addition on AME for the starter phase were significantly greater than for the other phases. A significant interaction between ME level and enzyme supplementation in growth stage (P < 0.05) was observed. The retention of CP decreased linearly with the reduction of ME level in diets (R2 = 0.245, P < 0.001 for starter; R2 = 0.367, P < 0.001 for grower). The retention of CP was increased by enzyme supplemented into the diets with ME levels of 11.55 and 11.80 MJ/ kg. Together, our results suggested that the ME level of diet affected the digestibility of DM, energy, and CP, and enzyme supplementation improved energy digestibility in diets with lower levels of ME.

Key Words: enzyme preparation • broiler • metabolizable energy • dry matter • crude protein


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Numerous studies of exogenous enzyme supplementation in broiler diets have been conducted, and improvements of the performance of broiler chicks and nutrient availability have been well documented. Supplementation with enzymes can help to eliminate the effects of antinutritional factors and improve the utilization of dietary energy and amino acids, resulting in improved performance of chicks (Rotter et al., 1990; Fuente et al., 1995; Cowan et al., 1996; Marquardt et al., 1996; Yu et al., 2007). In the poultry industry, enzymes have been added to broiler diets for more than 30 yr. The ME level of diet is one of the key factors for rapid growth of broiler chicks. Addition of enzymes to feed ingredients for improving energy availability has received much attention by animal nutritionists and feed manufacturers. Fuente et al. (1995) found that enzyme addition significantly increased the AMEn of diets (13.45 vs. 13.71 MJ/kg of DM) in 30-d-old chicks, but did not see any increase in 10-d-old chicks. Rotter et al. (1990) noticed a different response to enzyme addition of young chicks (AMEn) compared with that of adult roosters (TMEn). Another experiment by Zanella et al. (1999) demonstrated that chickens receiving a lower energy diet supplemented with a multi-enzyme product of amylase, protease, and xylanase achieved the same growth performance as a maize-soybean basal diet and increased protein digestibility by 2.9%. The level of improvement of energy availability is related to enzyme type and dosage, correlating well with the substrate specificity of the various enzymes present in the diet. Diet is formulated based on the specific nutrient value of available feed ingredients. These ingredients are combined in a diet to give the required nutrient level at minimal cost. It is applicable for some producers to use a modified factor of energy density when enzymes are included in feeds to offset the cost of enzyme addition. This may be achieved by assigning a specific energy value to the enzyme or by reducing the energy specification of the diet by 3 to 4% (Cowan et al., 1996). The factor of age was also found to influence the response of birds to an enzyme supplementation to a barley-based diet in both growth (Petterson et al., 1991) and nutrient digestibility (Salih et al., 1991). Previously, researchers have mostly focused on the energy improvement of barley-, wheat-, rye-, and oats-based diets supplemented with nonstarch polysaccharide enzymes. Corn-soybean meal-based diets with different ME levels and ages of birds have received less attention. Therefore, the aim of the current trial was to study the efficiency of energy improvement in broiler diets with different ME levels by supplementation of enzyme preparation.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Diets and Enzymes

The trial diets were formulated with 5 ME levels of 12.55, 12.30, 12.05, 11.80, and 11.55 MJ/kg; 3 phases (starter, grower, finisher); and 2 enzyme inclusion rates (0 or 750 mg/kg). The composition of the 3 phase experimental basal diets are shown in Table 1Go, Table 2Go, and Table 3Go.


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  		Table 1. Composition of experimental starter diets
 

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  		Table 2. Composition of experimental grower diets
 

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  		Table 3. Composition of experimental finisher diets
 
The enzyme preparation used in this study was a commercial multi-enzyme complex (Yiduozyme 9680, GuangDong, VTR Bio-Tech Co. Ltd., China), and provided (per kilogram of diet) 300, 2,500, and 2,000 units of xylanase, {alpha}-amylase, and protease, respectively. The activity of each enzyme was defined as the amount of enzyme that released 1 micromole of xylose at 50°C, pH 4.8, per minute for xylanase, released 1 microgram of tyrosine from hydrolyzing casein at 40°C, pH 3.5, per minute for protease, and hydrolyzed 1 milligram of soluble starch at 60°C, pH 6.0, per minute for amylase.

Birds and Sample Collection

Four hundred 1-d-old Arbor Acres broilers were obtained from a commercial hatchery and fed with commercial broiler starter, grower, and finisher diets until the age of 8, 18, and 38 d.

At 8 d of age, 100 chickens were transferred to metabolism cages, 1 chick per cage, with 10 treatments and 10 replicates per treatment. The metabolism cages were 0.19 m wide, 0.38 m long, and 0.35 m high and were placed in a building with controlled environmental conditions with sufficient ventilation and an artificial lighting program. After 2 d of adaptation to experimental diets, birds were fasted for 16 h to empty gut digesta and endogenous enzymes, and then allowed ad libitum access to feed and water. Total excreta were collected twice daily (0800 and 1600 h) for 3 consecutive days, and birds were fasted for another 16 h before the end of the collection period. Feathers and shredded dry skin were removed carefully before excreta were stored in sealed plastic bags and preserved immediately in freezer (–20°C). Then, excreta samples from the same bird were pooled, dried for 24 h in an oven (75°C), and then ground before DM, energy, and nitrogen determinations.

The experiment was repeated at 18 d with the grower diet (Table 2Go) and at 38 d with the finisher diet (Table 3Go). The methodology was the same as that described above.

Chemical Analysis

Dry matter was analyzed by oven drying (AOAC International, 2005; method 934.01), CP by Kjeldahl method (AOAC International, 2005; method 955.04), and gross energy by bomb calorimeter in the Animal Nutrition Laboratory of Nanjing Agricultural University (Nanjing, China).

Statistical Analysis

Data obtained were analyzed by Excel, followed by the ANOVA and regression using GLM procedure of SAS (version 9.0; SAS Institute, 1991). The results were reported as means ± SD.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Apparent Digestibility of DM

The apparent digestibility of DM in broilers of different phase is shown in Table 4Go. The apparent digestibility of DM decreased linearly with the reduction in ME level in diets (R2 = 0.234, P < 0.001 for starter phase; R2 = 0.362, P < 0.001 for grower phase). The apparent digestibility of DM increased with enzyme supplementation for all diets. Enzyme supplementation improved the apparent digestibility of DM by 0.45 to 3.88 percentage units, 0.87 to 3.35 percentage units, and 0.70 to 2.54 percentage units in starter, grower, and finisher phases of broilers, respectively. The largest improvement occurred in the diet with the lowest ME level (11.55 MJ/kg). There was no significant interaction between the effect of energy level and enzyme, energy level and growth phase, enzyme and growth phase, or energy and growth phase.


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  		Table 4. The effect of enzyme addition on the apparent digestibility of DM (mean ± SD) in broilers diets
 
AME

The AME value decreased linearly with the reduction in ME level in diets (R2 = 0.418, P < 0.001 for starter phase; R2 = 0.398, P < 0.001 for grower phase; R2 = 0.097, P = 0.027 for finisher phase) as shown in Table 5Go and Figure 1Go. Enzyme supplementation enhanced AME values of diets in starter, grower, and finisher phases, respectively, by 0.07 to 0.62, 0.15 to 0.56, and 0.12 to 0.43 MJ/kg. The diet with the ME of 11.55 MJ/kg at starter and finisher phase had the greatest improvement of AME value with enzyme supplementation .The effect of enzyme addition on AME for the starter phase was significantly greater than that for other phases, and enzyme addition at 750 mg/kg had a energy improvement value of 0.62 MJ/kg. There was a significant interaction between ME level and enzyme supplementation in the grower phase (P < 0.05).


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  		Table 5. The effect of enzyme addition on the AME in broiler diets
 

Figure 1
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  		Figure 1. Effects of enzyme supplementation on the AME (5 levels, MJ/kg) in broiler starter diets.

 
Apparent Digestibility of CP

The retention of CP decreased linearly with the reduction in ME level in diets (R2 = 0.245, P < 0.001for starter phase; R2 = 0.367, P < 0.001 for grower phase; Table 6Go). Enzyme supplementation in all diets increased the apparent retention of CP (ADCP). The ADCP was improved by –1.31 to 5.09 percentage units, 0.02 to 6.26 percentage units, and –0.8 to 3.96 percentage units, with enzyme supplementation for starter, grower, and finisher phases of broilers, respectively. The ADCP was increased with enzyme supplementation to the diets with ME levels of 11.55 and 11.80 MJ/kg. However, ADCP decreased in the diets with ME levels of 12.55 and 12.30 MJ/kg. There was a significant interaction between ME level and enzyme supplementation in the grower phase (P < 0.05).


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  		Table 6. The effect of enzyme addition on the apparent retention of crude protein in broiler diets
 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
In general, the ME level of corn-soybean meal diets depends on the digestibility of starch, nonstarch poly-saccharides (NSP), and protein. Meng and Slominski (2005) observed improved efficiency in the ME value of corn, corn-soybean meal, corn-canola meal, and corn-pea based diets when a multi-carbohydrase preparation was used, which was attributed to the improved digestibility of starch and NSP, but the retention of CP was not affected by enzyme supplementation. The improvement of AME and apparent digestibility of DM in diets with enzyme addition in the current study was inconsistent with the previous report (Meng and Slominski, 2005). Kocher et al. (2003) found that the combined addition of pectinase, protease, and amylase significantly improved AMEn when added to a corn-soybean meal basal diet with lower energy and protein levels. Similar results were obtained in other studies with lupin, barley, and wheat basal diets (Rotter et al., 1990; Fuente et al., 1995; Cowan et al., 1996; Steenfeldt et al., 2003). However, McCracken and Quintin (2000) reported that there was no significant effect of enzyme addition on the measured AME content of the diets.

The present study demonstrated that the improved values of AME in lower energy diets were greater than that of higher energy diets. This agreed with the result obtained by Kocher et al. (2003). The improvement of AME was only 0.54 to 1.48% for higher energy diets (12.55 and 12.30 MJ/kg) but it was 2.03 to 5.33% in lower energy diets, which is similar to the improvement level of AME by enzyme supplementation proposed by Cowan et al. (1996), suggesting enzyme supplementation to low nutrient level diets had greater beneficial effect than supplementation to high level diets. It suggested that enzyme supplementation to lower nutrient level diets had a greater beneficial effect. This will be practicable for producers to reduce the AME of diets by 3 to 4% in feed formulas and therefore has a cost benefit. Scott (1996) reported that AME values determined at 8 d of age were lower than that at 14 to 17 d, implying that the limited digestive capacity of young broilers can be improved by age. Olukosi et al. (2007) observed that the ME and retention of DM, energy, and N increased with increasing age of the birds. They concluded that the chicks benefited more from enzyme addition at a younger age and that the contribution of the enzymes to nutrient retention decreased with age in chickens. The effect of age on the AME, however, was not observed in this study, similar to the report of Fuente et al. (1995). This difference was attributed to the age of chickens used in experiments and diet formulas. The absorptive capacity of chicks in the first week after hatching is limited, but usually attains the absorptive peak by the middle of the second week of life (Mahagna and Nir, 1996). The determined values of AME for birds at 7 or 8 d of age were significantly lower than those at or after 14 d. However, there was less difference or no significant difference between AME determined at d 14 and that determined at later ages (Lopez and Leeson, 2007; Olukosi et al., 2007). Interestingly, a slightly greater digestibility of either DM or N at 13 to 15 d of age was observed from a commercial broiler hybrid compared with that at older ages (Ten Doeschate et al., 1993). These data suggested that birds can reach maturation in their digestive capacity at an early stage. Therefore, birds at 11 to 14 d, 21 to 24 d, and 41 to 44 d of age (as used in our study) should have functional, mature digestive organs and high nutrient digestibility.

The ingredients of diet formula also affect the determined results of nutrient digestibility. To make it more applicable to local industrial practices and develop isoprotein treatments at minimal dietary cost, the ingredients used in the diets of this study consisted of multiple sources including corn, soybean meal, fish meal, rapeseed meal, wheat red dog, and wheat bran. Wheat bran, wheat red dog, and rapeseed meal contain greater amounts of antinutritional factors such as NSP and phytic acid, which might limit nutrient digestibility but can be degraded by enzymes. It was suggested that grower and finisher diets formulated with the lowest AME of 11.55 MJ/kg contained much more wheat bran, which may contribute to lower digestibility of DM and CP. Fish meal, on the other hand, would affect determined results of nutrients in terms of increasing nutrient retention for its high availability of nutrients to animals (NRC, 1994). Garcia et al. (2007) demonstrated that there was no difference between the amino acid (AA) digestibility at 7 and 21 d of age in a chick assay for the majority of the indispensable AA in several feed ingredients including fish meal, and those diets had greater AA digestibility at the early age of 7 and 21 d. Additionally, the negative effects of acute coccidiosis infection on nitrogen-corrected ME and AA digestibility could alleviate for chicks fed fish meal diets (Persia et al., 2006). The fish meal diets had greater digestibility of DM and CP in our study. The influence of enzyme supplementation on ADCP was not consistent, but enzyme addition increased the ADCP in the lower energy diets (11.80 and 11.55 MJ/kg).

In conclusion, the improvement of AME content by enzyme supplementation was relation to ME in broiler diets. We suggested that compared to the high-AME diet, enzyme supplementation to low-AME feed ingredients would be more efficient and necessary.


   ACKNOWLEDGMENTS
 
The authors acknowledge the GuangDong VTR Bio-Tech Co. Ltd. for providing the enzyme preparation sample and for financial support of this study. We thank Shi Fangxiong for the English correction on our draft manuscript.

Received for publication June 7, 2008. Accepted for publication October 14, 2008.


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 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
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Fuente, J. M., P. Pkrez de Ayala, and M. J. Villamide. 1995. Effect of dietary enzyme on the metabolizable energy of diets with increasing levels of barley fed to broilers at different ages. Anim. Feed Sci. Technol. 56:45–53.

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Lopez, G., and S. Leeson. 2007. Relevance of nitrogen correction for assessment of metabolizable energy with broilers to forty-nine days of age. Poult. Sci. 86:1696–1704.[Abstract/Free Full Text]

Mahagna, M., and I. Nir. 1996. Comparative development of digestive organs, intestinal dissacharidases and some blood metabolites in broilers and layer-type chicks after hatching. Br. Poult. Sci. 37:359–371.[Web of Science][Medline]

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Meng, X., and B. A. Slominski. 2005. Nutritive values of corn, soybean meal, canola meal and peas for broiler chickens as affected by a multicarbohydrase preparation of cell wall degrading enzymes. Poult. Sci. 84:1242–1251.[Abstract/Free Full Text]

NRC. 1994. Nutrient Requirements of Poultry. 9th rev. ed. National Academy Press, Washington, DC.

Olukosi, O. A., A. J. Cowieson, and O. Adeola. 2007. Age-related influence of a cocktail of xylanase, amylase and protease or phytase individually or in combination in broilers. Poult. Sci. 86:77–86.[Abstract/Free Full Text]

Persia, M. E., E. L. Young, P. L. Utterback, and C. M. Parsons. 2006. Effects of dietary ingredients and Eimeria acervulina infection on chick performance, apparent metabolizable energy, and amino acid digestibility. Poult. Sci. 85:48–55.[Abstract/Free Full Text]

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