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J APPL POULT RES 2008. 17:482-489. doi:10.3382/japr.2008-00045
© 2008 Poultry Science Association
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Research Reports

Evaluation of Heat-Stable Phytases in Pelleted Diets Fed to Broilers from Day Zero to Thirty-Five During the Summer Months

J. R. Timmons*,1, R. Angel{dagger}, J. M. Harter-Dennis{ddagger}, W. W. Saylor§ and N. E. Ward#

* Maryland Cooperative Extension, Lower Eastern Shore Research and Education Center, University of Maryland, 27664 Nanticoke Road, Salisbury 21801; {dagger} Department of Animal and Avian Sciences, University of Maryland, College Park 20742; {ddagger} Department of Agriculture, University of Maryland Eastern Shore, Princess Anne 21853; § Department of Animal and Food Sciences, University of Delaware, Newark 19716; and # DSM Nutritional Products Inc., Parsippany, NJ 07054

Correspondence: 1 Corresponding author: mdchick{at}umd.edu


   SUMMARY
TOP
 SUMMARY
DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Supplementing phytase to broiler diets has been shown to improve phytate P digestibility in commercial broilers. Broiler rations are typically pelleted to promote improved broiler performance, but high pelleting temperatures can inactivate phytase enzymes. Before the introduction of heat-stable phytase products, phytase enzymes were generally added postpelleting to limit the effect of pelleting temperature on phytase activity. Therefore, the objective of this study was to evaluate postpelleting phytase activity of 3 concentrations of 2 heat-stable phytase enzymes and their efficacy when fed to 0- to 35-d-old broilers. After pelleting the phytase-supplemented diets at 93.3°C, the retained phytase activities of the 2 enzymes were similar, suggesting equivalent heat stability. Supplementing phytase to deficient nonphytate P diets improved FCR by 3% (P ≤ 0.05) compared with the FCR of birds fed an unsupplemented deficient diet. No differences in tibia ash (TA) were detected between the 2 phytase sources; however, TA of birds fed supplemental phytase at the 2 greatest concentrations was improved (P ≤ 0.05) compared with the TA of birds fed nonphytate P-deficient diet. These results suggest that the prepelleting inclusion of heat-stable phytase enzymes may be a viable alternative to postpellet application of phytase for improving P utilization in broilers.

Key Words: broiler • phytase • nonphytate phosphorus • pelleting


   DESCRIPTION OF PROBLEM
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Phytate P represents 50 to 80% of the total P present in feedstuffs commonly used in poultry diets [1–3]. Research has shown that poultry have a limited ability to utilize this form of P. Phytase enzymes are commonly used in poultry diets to catalyze the release of P bound to phytate [4] and improve phytate P utilization in commercial poultry [5–8]. Phytases can be obtained from a variety of sources [9] and have been widely produced for commercial swine and poultry diets for several years.

Broiler rations are typically pelleted to promote enhanced weight gain (WG) and FCR [10–12]. Pelleting is achieved through a mechanical process in combination with moisture, heat, and pressure [13]. Typically, feed moisture should be 17 to 18%, and the temperature should reach 82°C to gelatinize and bind the starches in the grains [13], but optimal pelleting temperature will be determined by the mash temperature and the temperature change required to achieve the desired pellet quality. In some cases, feed manufacturers may increase pelleting temperatures in response to food safety concerns. A limitation to most commercially available phytases is that they are inactivated when pelleted (>70°C) [14]. Before the advent of heat-stable phytase product forms, phytases were generally added postpelleting to prevent inactivation due to high pelleting temperatures. Phytases with improved thermostability would increase their practical applications for inclusion into poultry diets. Glycosylation of a phytase produced by Aspergillus niger has been reported to increase heat stability [15]. Some phytases are produced with a specialized coating to protect them from the high temperatures that occur during the feed manufacturing process. The objective of this study was to evaluate the heat stability of 2 heat-stable phytase enzymes after pelleting and the efficacy of these pelleted phytase enzymes when fed to 0- to 35-d-old mixed-sexed broilers.


   MATERIALS AND METHODS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
General Procedures
All animal procedures were approved by the University of Maryland Eastern Shore Institutional Animal Care and Use Committee. A 35-d floor pen trial was conducted between June and July 2007 using Ross 708 mixed-sex broilers obtained from a commercial hatchery [16] at day of hatch. Broilers (22 females and 22 males per pen, placement density of 0.089 m2 per bird) were raised in floor pens (8 pens per treatment; TRT) with used wood shavings. The broiler house was equipped with sidewall curtains and was mechanically ventilated using a positive pressure tube system. All pens were equipped with nipple drinkers and radiant heaters. The light program mimicked industry conditions and consisted of 24 L:0D for the first 4 d, 16L:8D from 5 to 10 d, 18L:6D from 11 to 14 d, and 22L:2D from 15 to 35 d of age. The target light intensities were 1.5 to 3.0, 0.75 to 1.0, and 0.2 to 0.5 foot-candles from 0 to 10, 11 to 26, and 27 to 35 d of age, respectively. Temperatures were uniform across all TRT and were maintained at 35°C from hatch to 5 d, 30°C from 6 to 10 d, and 25°C from 11 to 15 d, after which no additional heat sources were used. House temperature during the experiment was monitored throughout the study with a Cox Tracer (accuracy ± 0.3°C) [17]. Average temperature throughout the study was 30°C ± 3.2 SD.

Feed and water were offered ad libitum, and any dead birds were weighed and recorded daily by pen. Three dietary phases were used in this study: starter (St) from hatch to 21 d, grower (Gr) from 22 to 28 d, and finisher (Fn) from 29 to 35 d of age. Pen weights were determined at placement (day of hatch), 21 d, and 35 d of age. Feed consumption (FC) was determined for each feed phase, and FCR (feed:gain; not corrected for mortality) was determined from hatch to 21, 22, to 35 and hatch to 35 d of age. Three females and 3 males that were randomly selected from each pen at the end of the St and Fn phases were killed by cervical dislocation, and the right tibias were removed. All tissues, including the cartilage cap, were removed, and dry defatted tibia ash percentage (TA) was determined [18].

Diets
One basal diet was formulated and mixed for each feeding phase for all TRT (Table 1Go). The basal diet was analyzed for P by colorimetric determination [19] and Ca by atomic absorption spectroscopy [20, 21]. The basal diets (BD1; Table 1Go) represented 97.4, 97.6, and 98% of all TRT diets in the St, Gr, and Fn phases, respectively. Based on Ca and P analyzed values, defluorinated phosphate and calcium carbonate were added to achieve desired Ca and nonphytate P (nPP) concentrations. Using this basal diet, we mixed a second basal diet (BD2) for each phase for all diets containing phytase (Table 2Go). The second basal diet constituted 99.965% (BD1 plus calcium carbonate and defluorinated phosphate) of all the final diets that contained enzymes within each feed phase, such that enough space was left for addition of the phytases. Only 1 basal diet was mixed for all diets containing phytase per feed phase to minimize the impact of mixing on diet nutrient concentrations. Silica was added as a filler where needed so that all diets equaled 100%.


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  		Table 1. Ingredient composition and nutrient concentrations in the basal diets
 

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  		Table 2. Dietary treatment nutrient concentrations: formulated (analyzed)
 
Eight experimental TRT were tested including: P adequate (PA), low P (LP) concentration, and 3 concentrations of 2 phytase products. The PA diet met or exceeded NRC [22] recommendations for all nutrients including Ca and nPP (Table 2Go). The LP diets were formulated to contained 0.70, 0.70, and 0.60% Ca and 0.35, 0.25, and 0.16% nPP in the St, Gr, and Fn phases, respectively (Table 2Go). The diets for the phytase-containing TRT were formulated to contain 0.70, 0.70, and 0.60% Ca and 0.27, 0.18, and 0.11% nPP in the St, Gr, and Fn phases, respectively (Table 2Go). A greater nPP concentration was used in the LP diets to prevent excessive mortality from the deficient nPP concentrations required to allow for a greater response from the supplemental phytase.

Two phytase products were used: phytase A (PhyA) [23] and phytase B (PhyB) [24]. Each enzyme was used based on product-guaranteed concentrations at 3 amounts: one-half, full, and twice the concentration recommended by the manufacturer (0.5x, 1.0x, and 2.0x, respectively). Recommended concentrations for PhyA and B were 1,850 FYT (a unit of phytase)/kg and 500 phytase units/kg of feed, respectively, and each 1x concentration was projected to liberate 0.1% nPP. Phytase units (FTU/kg of feed) and FYT are both defined as the amount of enzyme that catalyzes the release of 1 µM insoluble P/min from 5.1 mM sodium phytate in pH 5.5 buffer at 37°C [25, 26].

Diets were pelleted through the California Pellet Mill [27] at an average pelleting temperature of 93.3°C. Pelleted feed batches were 544 kg for the St diets and 608 kg for each of the Gr and Fn diets. Conditioner temperature was 99°C, and time was 20 s. The pelleting rate was 22 min/ton, and pellet temperatures were taken at 1, 5, and 10 min into the pelleting run at the pellet die exit. Mash and pellet samples were taken for phytase analysis [28]. Each sample was subdivided into 3 subsamples. Two samples per diet and form (mash and pellet) were coded for duplicate blind submission to a commercial laboratory for phytase analysis [29]. Each blindly submitted sample was analyzed in duplicate. The third sample was retained and stored at 4°C. Phytase analysis results were used to determine phytase activity retained during pelleting.

Statistical Analysis
A randomized complete block design was used in this study, and the dependent variables were percentage of retained phytase activity, WG, FCR (feed:gain), FC, and TA. Data were analyzed using the GLM procedure for ANOVA [30] using pen mean as the experimental unit. Significant differences among TRT means were determined using Tukey’s honestly significant differences test with a 5% level of probability.


   RESULTS AND DISCUSSION
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 
Retained phytase activities (averaged over 3 dietary phases) of the 6 phytase-supplemented diets were not different between any of 6 diets (Table 3Go). The average retained phytase activity of PhyA and PhyB was 72.2 and 74.5%, respectively. These results suggest that heat stabilities of PhyA and PhyB are similar. Several studies have investigated the retained phytase activity of several phytase sources subjected to different temperatures with varying results [31–36]. Ward and Wilson [34] reported similar pelleting stability of the same PhyA used in the present study. The retained phytase activity reported ranged from 68 to 90% across pellet temperatures of 73 to 99°C with an average 68% retained phytase activity of feed pelleted at 93.3°C. Angel et al. [35] pelleted diets at 70, 80, and 90°C with 500 U/kg of PhyA and reported 77.2, 67.1, and 57.7% retained phytase activity, respectively. However, only 24.9% retained PhyA activity of a diet pelleted between 80 to 85°C was reported by Angel and Wyatt [36].


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  		Table 3. Retained phytase activity of diets1 pelleted at 93.3°C
 
Day-21 and d-35 WG were not affected by dietary TRT (Table 4Go). A numerical increase in 35-d WG was observed in birds fed the phytase diets (except 1.0x PhyA) when compared with WG of birds fed the LP diets, but these differences were not significant when Tukey’s honestly significant differences means separation test was performed. No differences in FC were detected from hatch to 21 d (Table 4Go); however, d 22 to 35 FC of birds (data not shown) fed 1.0x PhyA TRT (2,001 g) was almost 5% lower (P ≤ 0.05) compared with FC of birds fed PA TRT (2,100 g). No differences were detected in FCR of chicks on d 21; however, differences in FCR of 35-d-old birds were detected. No differences were seen in FCR of 35-d-old birds fed any of the phytase diets; however, the FCR of birds fed diets 2.0x PhyA, 0.5x PhyB, and 1.0x PhyB were 3% lower (P ≤ 0.05) than FCR of birds fed the LP diet (Table 4Go).


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  		Table 4. Performance and bone quality of 21- and 35-d-old broilers fed nonphytate P (nPP)-deficient pelleted diets1 supplemented with 3 concentrations of 2 phytase enzymes2
 
Several studies have reported improved performance of broilers fed pelleted phytase diets. Silversides et al. [37] evaluated 3 experimental phytase enzymes after pelleting above 80°C. The experimental enzymes were derived from a gene isolated from samples of Escherichia coli and cloned into 3 yeast organisms (A, B, and C) to increase thermal stability. Four concentrations (0, 150, 450, and 1,250 U/kg) of each enzyme were added to diets, pelleted, and fed to 0- to 21-d-old broilers. At the end of the study, it was reported that WG and FCR of birds fed the greatest concentration of enzyme B (793 g and 1.63, respectively) were improved (P ≤ 0.05) compared with those of birds fed the P-deficient diet (671 g and 1.76, respectively). Only enzyme B at the greatest concentration produced effects on WG that were similar to those of the P-adequate diet (799 g). In addition, FCR of the 2 greatest concentrations of enzyme B (1.67 and 1.63, respectively) were not different from the FCR of birds fed the P-adequate diet (1.62).

Similar results were reported by Angel and Wyatt [36] and Parr et al. [38] in 45- and 42-d trials, respectively. Angel and Wyatt [36] reported no differences in WG or FCR of birds fed an inherent thermotolerant phytase at 1,000 U/kg pelleted at 80 to 85°C (2.89 kg and 1.75) compared with the gain and FCR of birds fed an adequate nPP diet (2.88 kg and 1.75). Parr et al. [38] also reported equivalent WG and FCR of birds fed a P-deficient diet supplemented with a thermotolerant phytase and pelleted at 80°C compared with the WG and FCR of birds fed a P-adequate diet.

Although those studies did report improved broiler performance from supplementing phytase to nPP-deficient pelleted diets, they used pelleting temperatures that were much lower than those used in the current study. Ward et al. [39] evaluated the efficacy of a coated protected phytase pelleted at 99°C by a commercial feed mill and fed to 0- to 21-d-old male broilers. It was briefly reported that WG and FCR were improved (P ≤ 0.05) due to supplemental phytase at 750 and 1,000 FYT/kg (703 g, 1.34 and 710 g, 1.32, respectively) compared with performance of birds fed a nPP-deficient diet (677 g and 1.40).

Significant differences were detected in TA of 21- and 35-d-old birds (Table 4Go). On d 21, TA of birds fed the PA TRT (51%) was greater (P ≤ 0.05) than the TA of birds fed the other 7 TRT. Tibia ash of birds fed 1.0x PhyA, 2.0x PhyA, and 2.0x PhyB were greater (P ≤ 0.05) than TA of birds fed LP diets. However, when the same concentrations of each phytase were compared, no differences in TA were detected. Using a nonorthogonal single degree of freedom contrast comparison, we detected no significant phytase source x concentration interaction in d-21 TA. However, a linear and quadratic effect of phytase concentration (P ≤ 0.05) was detected in TA.

On d 35, TA of birds fed the PA TRT (50.5%) was greater (P ≤ 0.05) than TA of birds fed the LP, 0.5x PhyA, 1.0x PhyA, and 0.5x PhyB TRT (47.9, 48.9, 48.9, and 48.9%, respectively). However, TA of birds fed TRT 2.0x PhyA, 1.0x PhyB, and 2.0x PhyB (50.3, 49.5, and 50.1%, respectively) was not different than the TA of birds fed the PA diet, but the TA from these TRT were greater than the TA of LP TRT birds. No differences in TA were detected between any phytase TRT. In addition, no significant phytase source x concentration interaction was detected in TA, but a linear effect of phytase concentration (P ≤ 0.05) was detected in d-35 TA.

Many studies have observed a positive response in TA of birds fed a P-deficient diet supplemented with phytase [40–43]; however, they did not evaluate phytase efficacy after pelleting of the diet. Few publications have investigated the efficacy of supplemental phytase subjected to pelleting temperatures on broiler bone quality. Angel et al. [35], Angel and Wyatt [36], and Ward et al. [39] briefly reported results on the effects of one of the phytases (PhyA) used in this study. Ward et al. [39] found that PhyA included in a P-deficient St diet at 750 and 1,000 FYT/kg and pelleted at 99°C increased (P ≤ 0.05) TA of 21-d-old broilers (41.5 and 42.7%, respectively) compared with TA of chicks fed a P-deficient diet (37.3%). In contrast, Angel et al. [35] found the TA of 18-d-old chicks fed a pelleted diet (90°C) supplemented with 500 U/kg of PhyA (47.9%) was not equivalent to TA of chicks fed an adequate P diet (51.1%). Similarly, Angel and Wyatt [36] reported femur ash weight of 45-d-old broilers fed a pelleted diet (80 to 85°C) containing 500 U/kg of PhyA was lower (P ≤ 0.05) than femur ash weight of birds fed an adequate P diet.

It is clear from the results of this study pre-pelleting supplementation of deficient nPP diets with heat-stable phytases can be a viable alternative to postpellet application of phytase for improving P utilization in broilers. However, the efficacy of these heat-stable phytase enzymes on broiler performance and bone quality should be further investigated in broilers raised under industry conditions.


   CONCLUSIONS AND APPLICATIONS
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
REFERENCES AND NOTES
 

  1. Prepelleting supplementation of diets deficient in nPP with 2 heat-stable phytase enzymes at 3 concentrations had no significant effect on WG of 35-d-old broilers.
  2. The FCR and TA of 35-d-old broilers were significantly improved compared with the low-P TRT when 2.0x PhyA and 1.0x PhyB were added to a nPP-deficient diet.
  3. Retained phytase activities between the 2 phytase sources were similar when feeds were pelleted at 93.3°C.
  4. Pelleting heat-stable phytases may provide feed manufacturers with an alternative means to include phytase into nPP-deficient diets.


   REFERENCES AND NOTES
TOP
 SUMMARY
 DESCRIPTION OF PROBLEM
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 CONCLUSIONS AND APPLICATIONS
 REFERENCES AND NOTES
 

  1. Maga, J. A. 1982. Phytate: Its chemistry, occurrence, food interactions, nutritional significance, and methods of analysis. J. Agric. Food Chem. 30:1–8.[Medline]
  2. Caldwell, R. A. 1992. Effect of calcium and phytic acid on the activation of trypsinogen and the stability of trypsin. J. Agric. Food Chem. 40:43–46.[CrossRef][Web of Science]
  3. Pallauf, J., and G. Rimbach. 1997. Nutritional significance of phytic acid and phytase. Arch. Anim. Nutr. 50:301–319.[CrossRef][Web of Science]
  4. Bedford, M. R. 2000. Exogenous enzymes in monogastric nutrition—Their current value and future benefits. Anim. Feed Sci. Technol. 86:1–13.[CrossRef]
  5. Denbow, D. M., V. Ravindran, E. T. Kornegay, Z. Yi, and R. M. Hulet. 1995. Improving phosphorus availability in soybean meal for broilers by supplemental phytase. Poult. Sci. 74:1831–1842.[Web of Science][Medline]
  6. Sohail, S. S., and D. A. Roland Sr. 1999. Influence of supplemental phytase on performance of broilers four to six weeks of age. Poult. Sci. 78:550–555.[Abstract/Free Full Text]
  7. Timmons, J. R., J. M. Harter-Dennis, andA. E. Sefton. 2004. Evaluation of nonuniform application of phytase (simulated) on growth performance and bone quality in broiler chicks. J. Appl. Poult. Res. 13:311–318.[Abstract/Free Full Text]
  8. Yi, Z., E. T. Kornegay, V. Ravindran, and D. M. Denbow. 1996. Improving phytate phosphorus availability in corn and soybean meal for broilers using microbial phytase and calculation of phosphorus equivalency values for phytase. Poult. Sci. 75:240–249.[Web of Science][Medline]
  9. Wodzinski, R. J., and A. H. Ullah. 1996. Phytase. Adv. Appl. Microbiol. 42:263–303.[Web of Science][Medline]
  10. McNaughton, J. L., and F. N. Reece. 1984. Factors affecting pelleting response. Influence of dietary energy in broiler starter diets. Poult. Sci. 63:682–685.[Web of Science]
  11. Plavnik, I., E. Wax, D. Sklan, and S. Hurwitz. 1997. The response of broiler chickens and turkey poults to steam-pelleted diets supplemented with fat or carbohydrates. Poult. Sci. 76:1006–1013.[Abstract/Free Full Text]
  12. Reece, F. N., B. D. Lott, and J. W. Deaton. 1985. The effects of feed form, grinding method, energy level, and gender on broiler performance in a moderate (21°C) environment. Poult. Sci. 64:1834–1839.[Web of Science]
  13. Fairfield, D. 1994. Pelleting cost center. Pages 111–130 in Feed Management Technology IV. R. R. McEllhiney, ed. American Feed Industry Association Inc., Arlington, VA.
  14. Jongbloed, A. W., and P. A. Kemme. 1990. Effect of pelleting mixed feeds on phytase activity and apparent absorbability of phosphorus and calcium in pigs. Anim. Feed Sci. Technol. 28:233–242.[CrossRef]
  15. Han, Y., and X. G. Lei. 1999. Role of glycosylation in the functional expression of an Aspergillus niger phytase (PhyA) in Pichia pastoris. Arch. Biochem. Biophys. 364:83–90.[CrossRef][Web of Science][Medline]
  16. Mountaire Farms Inc., Princess Anne, MD.
  17. Poly Lam Products Corp., Williamsville, NY.
  18. Association of Official Analytical Chemists. 1990. Method 972.15. Page 328 in Official Methods of Analysis. 16th ed. Assoc. Off. Anal. Chem., Arlington, VA.
  19. Heinonen, J. K., and R. J. Lahti. 1981. A new and convenient colorimetric determination of inorganic orthophosphate and its application to the assay of inorganic pyrophosphatase. Anal. Biochem. 113:313–317.[CrossRef][Web of Science][Medline]
  20. Model 5100, Perkin-Elmer, Norwalk, CT.
  21. Perkin-Elmer. 1982. Analytical Methods for Atomic Absorption Spectrophotometry. Perkin-Elmer, Norwalk, CT.
  22. NRC. 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Press, Washington, DC.
  23. Ronozyme P-CT, DSM Nutritional Products Inc., Parsippany, NJ.
  24. Phyzyme XP-TPT, Danisco Animal Nutrition, Marlborough, Wiltshire, UK.
  25. The definition of phytase units does not describe buffer, buffer strength, enzyme cofactors, or time to complete the incubation.
  26. Ward, N. E., and D. R. Campbell. 2007. Phytase assessment requires understanding. Feedstuffs 79:26–28.
  27. California Pellet Mill Co., Merrimack, NH, model 3016-4, 125 horsepower, 1.52-m-long variable-drive feeder, 2-roller assembly, closed-end corrugation, standard retention steel shaft conditioner (C18LL6.5), 5/32 CPX die 5-cm thick, steam hardness 272/499 kg/h, 8 ton/h feed production capacity.
  28. Engelen, A. J., F. C. Van der Heeft, P. H. G. Randsdorp, and E. L. C. Smit. 1994. Simple and rapid determination of phytase activity. J. AOAC Int. 77:760–764.[Web of Science][Medline]
  29. DSM Nutritional Products Inc. Parsippany, NJ.
  30. Statistix for Windows 2.0. 1998. Analysis Software, Tallahassee, FL.
  31. Pasamontes, L., M. Haiker, M. Wyss, M. Tessier, and A. van Loon. 1997. Gene cloning, purification, and characterization of a heat-stable phytase from the fungus Aspergillus fumigatus. Appl. Environ. Microbiol. 63:1696–1700.[Abstract]
  32. Wyss, M., L. Pasamontes, R. Remy, J. Kohler, E. Kusznir, M. Gadient, F. Muller, and A. van Loon. 1998. Comparison of the thermostability properties of three acid phosphatases from molds: Aspergillus fumigatus phytase, A. niger phytase, and A. niger pH 2.5 acid phosphatase. Appl. Environ. Microbiol. 64:4446–4451.[Abstract/Free Full Text]
  33. Garrett, J. B., K. A. Kretz, E. O’Donoghue, J. Kerovuo, W. Kim, N. Barton, G. Hazlewood, J. M. Short, D. E. Robertson, and K. A. Gray. 2004. Enhancing the thermal tolerance and gastric performance of a microbial phytase for use as phosphate mobilizing monogastric-feed supplement. Appl. Environ. Microbiol. 70:3041–3046.[Abstract/Free Full Text]
  34. Ward, N. E., and J. W. Wilson. 2001. Pelleting stability of RonozymeTM P CT phytase in commercial feedmills. Poult. Sci. 80(Suppl. 1):1968. (Abstr.)
  35. Angel, R., N. Ward, and A. Mitchell. 2006. Effect of pelleting temperature and phytase type on phytase survivability and broiler performance. Poult. Sci. 85(Suppl. 1):10. (Abstr.)
  36. Angel, R., and C. Wyatt. 2006. Effect of an evolved thermo-tolerant phytase on performance and bone ash in broiler chickens. Poult. Sci. 85(Suppl. 1):T14. (Abstr.)
  37. Silversides, F. G., T. A. Scott, and M. R. Bedford. 2004. The effect of phytase enzyme and level on nutrient extraction by broilers. Poult. Sci. 83:985–989.[Abstract/Free Full Text]
  38. Parr, T., C. Wyatt, and M. Bedford. 2006. Comparison of two phytases pelleted at two temperatures on broiler performance carcass yield. Poult. Sci. 85(Suppl. 1):S-T113. (Abstr.)
  39. Ward, N. E., J. W. Wilson, and J. McNaughton. 2001. Comparison of Ronozyme PTM CT, Ronozyme PTM Liquid, and Natuphos® Liquid in a commercial broiler pelleted feed. Poult. Sci. 80(Suppl. 1):1969. (Abstr.)
  40. Pillai, P. B., T. O’Connor-Dennie, C. M. Owens, and J. L. Emmert. 2006. Efficacy of an Escherichia coli phytase in broilers fed adequate or reduced phosphorus diets and its effect on carcass characteristics. Poult. Sci. 85:1737–1745.[Abstract/Free Full Text]
  41. Watson, B. C., J. O. Matthews, L. L. Southern, and J. L. Shelton. 2006. The effects of phytase on growth performance and intestinal transit time of broilers fed nutritionally adequate diets and diets deficient in calcium and phosphorus. Poult. Sci. 85:493–497.[Abstract/Free Full Text]
  42. Augspurger, N. I., D. M. Webel, X. G. Lei, and D. H. Baker. 2003. Efficacy of an E. coli phytase expressed in yeast for releasing phytate-bound phosphorus in young chicks and pigs. J. Anim. Sci. 81:474–483.[Abstract/Free Full Text]
  43. Dilger, R. N., E. M. Onyango, J. S. Sands, and O. Adeola. 2004. Evaluation of microbial phytase in broiler diets. Poult. Sci. 83:962–970.[Abstract/Free Full Text]




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