| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
METABOLISM AND NUTRITION |
* Department of Animal Sciences, University of Missouri, Columbia 65211; and USDA-ARS, National Small Grains Research Facility, Aberdeen, ID 83210
1 Corresponding author: ledouxd{at}missouri.edu.
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
Key Words: phytate • barley • zinc • chick • autoclaving
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
The addition of microbial phytase, an enzyme that hydrolyzes phytate, increases the bioavailability of phytate P, cations and protein in monogastric diets (Ravindran et al., 1995; Kies et al., 2001). Levels of supplemental phytase between 600 and 800 PPU (1 PPU = the amount of enzyme required to liberate 1 nM inorganic P from 2 mM sodium phytate per minute at pH 5.0 and 40°C)/kg of diet have shown the best results for improving P digestibility and retention in pigs and poultry (Kornegay, 2001). Diets formulated using ingredients having high endogenous phytase activity, such as wheat, barley, and triticale also promote greater absorption of phosphorus (Eeckhout and De Paepe, 1994). The addition of 800 PPU/kg of microbial phytase to broiler diets increased Zn retention and decreased Zn excretion (Thiel and Weigand, 1992). Biehl et al. (1995) reported that phytase and dihydroxycholecalciferol supplementation increased growth rate and tibia Zn concentration in chicks.
Another approach for improving P and Zn utilization is to develop feedstuffs with lower levels of phytic acid. Recently, USDA scientists developed several low phytate barley (LPB) mutants with reduced phytate P (50 to 90%) with no change in total P (Raboy, 2001). In recent studies, Guaiume et al. (2002) reported higher P and Zn retention in chicks fed LPB compared with wild-type barley (WTB), and Li et al. (2001a) reported that P availability from LPB was estimated to be 49% compared with 38% for WTB. Egli et al. (2004) reported that adult humans absorbed more Zn from a dephytinized wheat-soy diet compared with the nondephytinized diet (34.6 vs. 22.8%, respectively). Similarly, Adams et al. (2002) reported that substitution of normal corn by low phytate (LP) corn in a corn-based diet resulted in a substantial increase in Zn absorption by healthy adult humans.
The objectives of these studies were to evaluate the effects of LPB, which contains 90 to 95% less phytate P, on Zn and P utilization by young broiler chicks and to determine the contribution of endogenous phytase present in LPB on Zn and P utilization.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
, and the composition of the basal diets is presented in Table 2. Ground samples were analyzed for dry matter, ash, crude protein, and crude fiber (AOAC, 2000). Calcium, magnesium, iron, manganese, copper, and zinc were analyzed by flame atomic spectrophotometry. Amino acid content was measured by sample hydrolysis with quantification by HPLC (AOAC, 2000). The LPB used in this study was the M 955 mutant isolated from the cultivar Harrington used here as a check on the validity of the mutation. The M 955 LPB produces grain that has similar levels of total P when compared with the WTB control but contains 90 to 95% less phytate P (Dorsch et al., 2003; Ockenden et al., 2004). The LPB and WTB used in these experiments were provided by the USDA-Agricultural Research Service, Small Grains and Potato Research Unit, Aberdeen, ID. Chromic oxide was included in the diets as an inert marker at a concentration of 0.05% for determination of mineral retention. Ronozyme B [(endo-1,3(4)-ß-glucanase, 140 FBG/g (1 FBG unit = the amount of enzyme that releases 1.0 µM of glucose or reducing carbohydrates per minute at pH 5.0 and 30°C); endo-1,4-ß-xylanase, 600 FXU/g (1 FXU = the amount of enzyme that releases 7.8 µM of reducing xylose equivalents from azo-wheat arabinoxylan per minute at pH 6.0 and 50°C); 
-amylase, 50 KNU/g (1 KNU = the amount of enzyme that breaks down 5.26 g of starch per h at pH 7.1 and 37°C)] was also included at a level of 500 g/ton to avoid confounding effects caused by nonstarch polysaccharides. Endogenous phytase activity in the diets was measured according to Zyla et al. (2002). Barley was the only source of phytate in the diets. Phytate content of the barleys was determined according to Dorsch et al. (2003).
|
|
A total of ninety-six 1-d-old male chicks was randomly assigned to a 2 x 3 factorial [2 barley types (WTB or LPB) and 3 Zn levels (0, 10, or 20 mg of Zn/kg)] arrangement of treatments with 4 pen replicates of 4 chicks assigned to each of the 6 dietary treatments for 3 wk. Zinc was supplied as ZnSO4.
Experiment 2
A total of two hundred forty 1-d-old straight-run broiler chicks were randomly assigned to a 2 x 2 x 3 factorial [2 barley types (WTB or LPB), autoclaved (121°C, 20 kg/cm2, 20 min.) or nonautoclaved, and 3 Zn levels (0, 10, or 20 mg of Zn/kg)] arrangement of treatments with 4 pen replicates of 5 chicks assigned to each of the 12 dietary treatments for 3 wk. Zinc was supplied as ZnSO4.
Measurements
During wk 3, excreta samples (4 pens/treatment) were collected for 5 consecutive days to determine P, Ca, and Zn retention. Daily excreta output was homogenized, and a 10% aliquot was collected, pooled, and frozen for subsequent analysis. At the end of the experiments, chicks were weighed by pen. Feed consumption was recorded at the same time, and feed conversion was calculated.
Chicks were then euthanized with carbon dioxide, and the middle toe from each foot and right tibia (3 chicks per pen) were collected.
For toe ash determination, toes were dried at 100°C for 24 h, weighed, and dry ashed in a muffle furnace at 540°C overnight. For tibia ash determination, right tibia were stripped of adhering tissue following immersion in boiling water, ether extracted, dried at 100°C for 24 h, weighed, and dry ashed in a muffle furnace at 540°C overnight. These procedures for bone ash determination are similar to those reported previously (Potter et al., 1995; Garcia and Dale, 2006) except that samples were ashed at 540°C to prevent zinc volatilization. Excreta and feed samples were dried at 60°C and ground through a 1-mm stainless steel screen. Bone ash and duplicate samples of excreta and feed were digested by nitric-perchloric acid wet digestion. Phosphorus concentrations in feed and excreta were determined colorimetrically by the mo-lybdo-vanadate method (AOAC, 2000). Calcium, Zn, and Cr concentrations in the bone, feed and excreta were determined by flame atomic absorption spectrophotometry, and the assay was validated by including standard reference material (peach leaves) from the National Institute of Standards and Technology. Phosphorus, Ca, and Zn retention were calculated using the following formula: 100% – [100% x (Cr concentration in feed or excreta) x (P or Ca or Zn concentration in feed or excreta)].
The animal care and use protocol for these studies was reviewed and approved by the University of Missouri-Columbia Animal Care and Use Committee.
Statistical Analysis
Data were analyzed as a 2 x 3 factorial (experiment 1) and 2 x 2 x 3 factorial (experiment 2) by ANOVA using the GLM procedures of SAS (SAS Institute, 1996). The means for treatments showing significant differences in the ANOVA were compared using Fisher’s protected least significant difference procedure. Statistical significance was accepted at P 
0.05.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
No barley type x Zn level interactions were observed (P > 0.05) for performance data (Table 3). Feed intake, body weight gain, and feed conversion were not affected (P > 0.05) by barley type. However, chicks fed diets with 10 and 20 mg/kg of supplemental Zn had higher (P < 0.05) feed intake and body weight gain than chicks fed diets with no supplemental Zn.
|
). Percent toe ash was affected (P < 0.05) by barley type. However, percent tibia ash was not affected (P > 0.05) by barley type (Table 4). Supplemental Zn did not affect (P > 0.05) percent toe or tibia ash. However, Zn concentration in toes and tibias increased (P < 0.0001) with increasing levels of dietary Zn and was higher (P < 0.0001) in chicks fed LPB compared with those fed WTB. Significant barley type x Zn level interactions (P < 0.0001) were observed for toe Zn (TZ) and tibia Zn (TBZ; Table 4). In chicks fed WTB, toe Zn and tibia Zn increased with increasing Zn supplementation, whereas the consistently high levels of toe Zn and tibia Zn in chicks fed LPB were not affected by higher concentrations of supplemental Zn.
|
). Zinc retention was higher (P < 0.001) in chicks fed LPB but declined with increasing Zn supplementation. A significant barley type x Zn level interaction (P < 0.0001) was also observed for Zn retention (Table 5).
|
No interactions between barley type, Zn level, or autoclaving were observed for performance variables (Table 6). Feed intake and body weight gain were higher (P < 0.05) in chicks fed LPB compared with chicks fed WTB but were not affected (P > 0.05) by Zn level or autoclaving process (Table 6). Feed conversion was not affected (P > 0.05) by dietary treatments.
|
). However, zinc concentration in toes and tibias increased (P < 0.0001) with increasing levels of dietary Zn and were higher (P < 0.0001) in chicks fed LPB compared with those fed WTB (Table 7). In chicks fed WTB, toe Zn and tibia Zn increased with increasing Zn supplementation, whereas similar to results in experiment 1, in chicks fed LPB increasing Zn supplementation did not further increase the already high toe and tibia Zn. This resulted in a significant (P < 0.0001) barley type x zinc level interaction (Table 7). No main or interactive effects of autoclaving were observed for bone ash.
|
). Calcium retention in broiler chicks was not affected (P > 0.05) by barley type. However, Ca retention was lower (P < 0.05) in chicks fed 20 mg of Zn/kg compared with chicks fed 0 or 10 mg of Zn/kg (Table 8). Chicks fed LPB retained more Zn (P < 0.001) than chicks fed WTB. Zinc retention decreased (P < 0.0001) with zinc supplementation (Table 8). The difference in Zn retention between the 2 barley types was much greater at zero compared with 10 or 20 mg of supplemental Zn/kg, resulting in a significant (P < 0.05) barley type x Zn level interaction (Table 8). No main or interactive effects of autoclaving were observed for P, Ca, or Zn retention.
|
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
The NRC (1994) states that 40 mg of zinc/kg of diet is optimal for chick growth; therefore in these experiments, dietary levels of zinc were used that ranged from deficient (24 mg/kg) to adequate (48 mg/kg). Results of experiment 1 indicated that the basal diet (~24 mg of Zn/kg) required an additional 10 mg of Zn/kg to maximize chick performance. In contrast, in experiment 2, Zn level in the basal diet (~27 mg/kg) was enough to meet the requirement for chick growth because additional Zn did not further improve chick growth. Similar results to that of experiment 2 were reported by Guaiume et al. (2002), who observed no difference in growth performance of chicks fed diets containing WTB and LPB and supplemented with 0, 10, and 20 mg of Zn/kg of diet. These results suggest that the Zn requirement of chicks fed a barley-based diet may be less than 40 mg/kg but higher than 24 mg/kg. However, Mohanna and Nys (1999) reported that a dietary Zn concentration of 45 mg/kg gave the best performance in broilers fed corn-soybean meal-wheat diets from hatch to 21 d of age.
Percentage tibia ash was not affected by dietary treatments in either experiment. In experiment 1, percent toe ash in the WTB treatment was higher than in the LPB treatment. However, there was no significant difference in toe ash weight (mg) between barley types (462 and 453 mg of toe ash for WTB and LPB, respectively). These contrasting results may be due to the influence of soft tissue (cartilage and skin) present on the toes, on percent toe ash determination. In contrast, toe ash weight would not be influenced by soft tissue. However, in previous studies with turkey poults (Li et al., 2001b) and broiler chicks (Linares et al., 2003) fed diets containing NRC levels of nonphytate P, no differences in percent tibia or toe ash were observed between chicks fed WTB or LPB. Research with chicks fed LP corn have also shown bone mineralization equal to or superior to those fed diets with normal corn (Li et al., 2000; Waldroup et al., 2000; Yan et al., 2000; Jang et al., 2003) and equal levels of nonphytate P.
As expected, no effects of Zn level on percentage of bone ash in chicks were observed. Because Ca and P are the major components of bones and the levels of these minerals in the diets were kept at NRC (1994) recommended levels, minimal differences in dietary Zn content did not affect bone mineralization. In agreement with this study, Yi et al. (1996) and Mohanna and Nys (1999) also did not observe effects of Zn level on percentage of bone ash in broilers.
Toe and tibia Zn were higher in chicks fed LPB compared with those fed WTB in both experiments. These results are consistent with previous reports by Guaiume et al. (2002) and Jang et al. (2003) who also observed increased bone Zn in chicks fed LPB compared with those fed WTB. Increased levels of phytic acid in feed have been shown to cause a decrease in Zn absorption in humans (Adams et al., 2002; Egli et al., 2004) and a decrease in Zn concentration in rat femurs (Atwal et al., 1980; Morris and Ellis, 1980). The addition of 10 and 20 mg of Zn/kg to the low Zn diets resulted in an increase of TBZ content by 18 and 28% and TZ content by 18 and 22%, respectively, in experiment 1. In experiment 2, the addition of 10 and 20 mg of Zn/kg to the low Zn diets resulted in an increase of TBZ content by 20 and 38% and TZ content by 16 and 32%, respectively, but this increase was only observed in chicks fed WTB. Increased TZ and TBZ concentration with increasing dietary Zn observed in this study is consistent with previous studies (Biehl et al., 1995; Yi et al., 1996; Mohanna and Nys, 1999; Guaiume et al., 2002). The magnitude of change in TZ and TBZ content in response to increasing concentrations of dietary Zn confirms previous reports indicating that bone Zn measurements are sensitive indicators for determining Zn utilization.
Significant barley type x Zn level interactions were also observed for TZ and TBZ. In chicks fed WTB, toe Zn and tibia Zn increased with increasing Zn supplementation, whereas in chicks fed LPB, toe Zn and tibia Zn did not increase with supplemental Zn. These results indicate that the diet containing LPB with no supplemental Zn supplied enough Zn to maximize TZ and TBZ concentrations, whereas in the diets containing WTB, toe Zn and tibia Zn concentrations continued to increase with increasing levels of supplemental Zn. These results also confirm previous reports (Li et al., 2001a,b) on the increased availability of Zn in LPB compared with WTB.
Chicks fed LPB diets retained 13.6 to 16.8% more P than chicks fed WTB diets, indicating that the availability of P from LPB is greater than that from WTB. Similar results were observed in chicks (Li et al., 2001a; Guaiume et al., 2002; Jang et al., 2003), turkeys (Li et al., 2001b), pigs (Veum et al., 2001), and fish (Sugiura et al., 1999) fed LPB and WTB diets. The LPB used in this study (M 955) is the only grain or legume genotype currently available for research in which grain phytate is reduced by greater than 90%. Because barley was the only source of phytate in the experimental diets, differences in nutritional status or performance between chicks fed the WTB and LPB diets can, in a genetic sense, be attributed to the allelic difference in a single gene between WTB and LPB that results in this large reduction in grain phytate, and accompanying large increase in available P.
Phosphorus excretion decreased an average of 25.8% when LPB was used in chick diets, compared with WTB diets. This level of excreta P reduction is consistent with previous reports (Li et al., 2000, 2001b; Yan et al., 2000; Jang et al., 2003; Linares et al., 2003) in which reductions in P excretion ranged from 17 to 33% when poultry were fed diets containing LPB or LP corn compared with their wild-type counterparts. These reductions in excreta P concentrations are similar to reductions observed (28–30%) when phytase is used to replace 0.1 to 0.15% nonphytate P in broiler diets (Waldroup et al., 2000; Yan et al., 2000).
Zinc retention was significantly higher in chicks fed LPB (averaging 27.5% for both experiments) compared with chick fed WTB. Guaiume et al. (2002) observed similar results in chicks fed LPB and WTB and the same levels of supplemental Zn. Thiel and Weigand (1992) reported that the addition of microbial phytase to broiler diets increased Zn retention and decreased Zn excretion. More recently, Yi et al. (1996) reported that Zn retention from a low Zn diet (20 mg of Zn/kg) increased linearly in chicks fed increasing levels of phytase (150 to 600 U/kg of diet). These data taken together with results of the current study and that of Guaiume et al. (2002) suggest that a reduction in phytate content of diets, whether by using LP grains or supplemental phytase, should improve Zn utilization.
The decrease in Zn retention with increasing dietary Zn concentrations observed in the present study has been reported previously in chicks (Yi et al., 1996; Mohanna and Nys, 1999). Mohanna and Nys (1999) reported that only 8% of ingested Zn was retained when the diet contained 170 mg of Zn/kg, whereas Zn retention was 29, 25, and 19% in diets containing 20, 30, and 60 mg of Zn/kg, respectively. In the present study, Zn retention averaged 43% across all dietary treatments for both experiments, where the highest dietary Zn concentration was 48 mg/kg Zn.
A significant barley type x Zn level interaction also was observed for Zn retention in both experiments. Chicks fed both barley types showed a decrease in Zn retention when Zn supplementation was increased. However, the decrease in Zn retention was much greater in chicks fed LPB compared with those fed WTB. It appears that when Zn is limiting, more Zn is retained in the body for maintaining physiological functions, thus resulting in less Zn excretion in the waste. Baer and King (1984) and Wada et al. (1985) suggested that humans rapidly reduce Zn excretion in response to low Zn intake, and Ziegler et al. (1989) noticed that infants were able to increase Zn absorption efficiency and decrease excretion of endogenous Zn, thereby maintaining Zn balance, despite a drastic decrease in Zn intake. Also, increased Zn retention efficiency has been shown in rats (Huber and Gershoff, 1970) and in chicks (Emmert and Baker, 1995) with decreased Zn intakes. The results of the present study confirmed data from Guaiume et al. (2002), who also observed an interaction and main effects of Zn level and barley type in chicks fed LPB and WTB barley to 21 d.
Calcium retention in this study was not affected by substituting LPB for WTB in the diets. Similar results were also reported in turkeys (Li et al., 2001b), pigs (Veum et al., 2001), and fish (Sugiura et al., 1999) fed LPB and WTB. However, contrasting results were reported in fish fed LPB (Overturf et al., 2003) and in humans fed LP corn (Hambidge et al., 2005). The increase in Ca availability and absorption in the studies by Overturf et al. (2003) and Hambidge et al. (2005) are probably a consequence of the lower dietary Ca concentrations used in those studies. In this study, Ca retention declined with increasing Zn supplementation (0 mg/kg, 53.05%; 10 mg/kg, 52.34%; 20 mg/kg, 46.16%) indicating that Zn depressed Ca utilization, probably through the formation of an insoluble Ca-phytate-Zn complex, which decreases the absorption of both minerals (Kornegay, 2001).
No main or interactive effects of autoclaving were observed for any response variable. This may have occurred because of the low levels of endogenous phytase activity (183 and 190 PPU/kg for WTB and LPB, respectively) in the barley cultivars. Barley was the only ingredient that contained endogenous phytase activity, and when added at 60% in diets, it contributed with endogenous phytase of 110 PPU/kg for WTB and 114 PPU/kg for LPB diets. Thus, there was very little difference in phytase activity between the 2 barley diets. In addition, Eeckhout and De Paepe (1994) reported that plant phytase is only 58% as effective as microbial phytase, which would mean that the phytase activity (relative to microbial phytase) in these diets was only 64 and 66 PPU/kg, respectively. These levels of phytase may not have been high enough to cause improvements in mineral utilization. Therefore, it is not surprising that there were no main or interactive effects of autoclaving. In swine diets containing 482 PPU/kg of endogenous phytase activity from feedstuffs such as wheat, wheat middlings or barley, steam pelleting at approximately 80°C decreased the absorption of P and Ca by 10%. This was mainly due to a considerable reduction in the phytase activity (Jongbloed and Kemme, 1990). Edwards et al. (1999) observed no improvements in phytate P utilization by broilers when corn-soybean meal diets were pelletized or extruded. Using an in vitro procedure, Zyla et al. (1999) observed that autoclaving feed containing 55% wheat for 20 min remarkably decreased the amounts (76% reduction) of P liberated from the diet containing 282 to 377 PPU/kg of endogenous phytase activity.
Results of these studies indicated that chicks fed LPB were able to utilize more dietary P and Zn than chicks fed WTB. Therefore, diets containing LPB may not need to be supplemented with as much inorganic P and Zn. The combination of low levels of supplementary inorganic P and Zn and increased availability of both minerals in LPB may result in a significant reduction in P and Zn in poultry manure. Reduction of minerals in manure would contribute to a reduction in the potential for environmental pollution. Differences in Zn and P utilization by chicks fed WTB and LPB diets are due to differences in phytic acid content of the barleys and not due to endogenous phytase activity present in the grains.
|
ACKNOWLEDGMENTS |
|---|
Received for publication June 16, 2006. Accepted for publication October 8, 2006.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
AOAC. 2000. Official Methods of Analysis. Assoc. Off. Anal. Chem., Washington, DC.
Atwal, A. S., N. A. M. Eskin, B. E. McDonald, and M. Vasey-Genser. 1980. The effects of phytate on nitrogen utilization and zinc metabolism in young rats. Nutr. Rep. Int. 21:257–267.
Baer, M. T., and J. C. King. 1984. Tissue zinc levels and zinc excretion during experimental zinc depletion in young men. Am. J. Clin. Nutr. 39:556–570.
Biehl, R. R., D. H. Baker, and H. F. DeLuca. 1995. 1-hydroxylated cholecalciferol compounds act additively with microbial phytase to improve phosphorus, zinc and manganese in chicks fed soy-based diets. J. Nutr. 125:2407–2416.
Cheryan, M. 1980. Phytic acid interactions in food systems. Crit. Rev. Food Sci. Nutr. 13:297–335.[Medline]
Dorsch, J. A., A. Cook, K. A. Young, J. M. Anderson, A. T. Bauman, C. J. Volkmann, P. P. N. Murthy, and V. Raboy. 2003. Seed phosphorus and inositol phosphate phenotype of barley low phytic acid genotypes. Phytochem. 62:691–706.
Edwards, H. M., Jr., A. B. Carlos, A. B. Kasim, and R. T. Toledo. 1999. Effects of steam pelleting and extrusion on feed on phytate phosphorus utilization in broiler chickens. Poult. Sci. 78:96–101.
Eeckhout, W., and M. De Paepe. 1994. Total phosphorus, phytate-phosphorus and phytase activity in plant feedstuffs. Anim. Feed Sci. Technol. 47:19–29.
Egli, I., L. Davidsson, C. Zeder, T. Walczyk, and R. Hurrell. 2004. Dephytinization of a complementary food based on wheat and soy increases zinc, but not copper, apparent absorption in adults. J. Nutr. 134:1077–1080.
Emmert, J. L., and D. H. Baker. 1995. Zinc stores in chickens delay the onset of zinc deficiency symptoms. Poult. Sci. 74:1011–1021.[Web of Science][Medline]
Garcia, A. R., and N. M. Dale. 2006. Foot ash as means of quantifying bone mineralization in chicks. J. Appl. Poult. Res. 15:103–109.
Guaiume, E. A., J. N. Broomhead, D. R. Ledoux, T. L. Veum, V. Raboy, and K. Zyla. 2002. Zinc utilization is improved in broiler chicks fed a diet containing low phytic acid barley (Hordeum vulgare L.). Poult. Sci. 81(Suppl. 1):142. (Abstr.)
Hambidge, K. M., N. F. Krebs, J. L. Westcott, L. Sian, L. V. Miller, K. L. Peterson, and V. Raboy. 2005. Absorption of calcium from tortilla meals prepared from low-phytate maize. Am. J. Clin. Nutr. 82:84–87.
Huber, A. M., and S. N. Gershoff. 1970. Effects of dietary zinc and calcium on the retention and distribution of zinc in rats fed semipurified diets. J. Nutr. 100:949–954.
Jang, D. A., J. G. Fadel, K. C. Klasing, A. J. Mireles, Jr., R. A. Ersnt, K. A. Young, A. Cook, and V. Raboy. 2003. Evaluation of low-phytate corn and barley on broiler chick performance. Poult. Sci. 82:1914–1924.
Jongbloed, A. W., and P. A. Kemme. 1990. Effect of pelleting mixed feeds on phytase activity and the apparent absorbability of phosphorus and calcium in pigs. Anim. Feed Sci. Technol. 28:233–242.
Kies, A. K., K. H. F. Van Hemert, and W. C. Sauer. 2001. Effect of phytase on protein and amino acid digestibility and energy utilization. World’s Poult. Sci. J. 57:109–126.
Kornegay, E. T. 2001. Digestion of phosphorus and other nutrients: The role of phytases and factors influencing their activity. Pages 237–272 in Enzymes in Farm Animal Nutrition. CABI Publishing, New York, NY.
Lease, J. G. 1966. The effect of autoclaving sesame meal on its phytic acid content and on the availability of its zinc to the chick. Poult. Sci. 45:237–241.[Web of Science][Medline]
Li, Y. C., D. R. Ledoux, T. L. Veum, V. Raboy, and D. S. Ertl. 2000. Effects of low phytic acid corn on phosphorus utilization, performance, and bone mineralization in broiler chicks. Poult. Sci. 79:1444–1450.
Li, Y. C., D. R. Ledoux, T. L. Veum, V. Raboy, K. Zyla, and A. Wikiera. 2001a. Bioavailability of phosphorus in low phytic acid barley. J. Appl. Poult. Res. 10:86–91.[Medline]
Li, Y. C., D. R. Ledoux, T. L. Veum, V. Raboy, and K. Zyla. 2001b. Low phytic acid barley improves performance, bone mineralization, and phosphorus retention in turkey poults. J. Appl. Poult. Res. 10:178–185.
Linares, L. B., J. N. Broomhead, E. A. Guaiume, D. R. Ledoux, T. L. Veum, and V. Raboy. 2003. Low phytate barley and phytase reduces phosphorus excretion in broilers fed diets for 42 days. Poult. Sci. 82(Suppl. 1):94. (Abstr.)
Lo, G. S., S. L. Settle, F. H. Steinke, and D. T. Hopkins. 1981. Effect of phytate:zinc molar ratio and isolated soybean protein on zinc bioavailability. J. Nutr. 11:2223–2235.
Lonnerdal, B., A. S. Sandberg, B. Sandstrom, and C. Kunz. 1989. Inhibitory effects of phytic acid and other inositol phosphates on zinc and calcium absorption in suckling rats. J. Nutr. 119:211–214.
Mohanna, C., and Y. Nys. 1999. Effect of dietary zinc content and sources on the growth, body zinc deposition and retention, zinc excretion and immune response in chickens. Br. Poult. Sci. 40:108–114.[Web of Science][Medline]
Morris, E. R. 1986. Phytate and dietary mineral bioavailability. Pages 57–76 in Phytic Acid Chemistry and Application. Pilatus, Minneapolis, MN.
Morris, E. R., and R. Ellis. 1980. Effect of dietary phytate/zinc molar ratio on growth and bone zinc response of rats fed semipurified diets. J. Nutr. 110:1037–1045.
National Research Council (NRC). 1994. Nutrient Requirements of Poultry. 9th rev. ed. Natl. Acad. Sci., Washington, DC.
Oberleas, D., and B. F. Harland. 1996. Impact of phytic acid on nutrient availability. Pages 77–84 in Phytase in Animal Nutrition and Waste Management. BASF Corp., Mount Olive, NJ.
Oberleas, D., M. E. Muher, and B. L. O’Dell. 1966. Dietary metal-complexing agents and zinc availability in the rat. J. Nutr. 90:56.
Ockenden, I., J. A. Dorsch, M. M. Reid, L. Lin, L. K. Grant, V. Raboy, and J. N. A. Lott. 2004. Characterization of the storage of phosphorus, inositol phosphate and cations in grain tissues of four barley (Hordeum vulgare L.) low phytic acid genotypes. Plant Sci. 167:114.
O’Dell, B. L., and J. E. Savage. 1960. Effect of phytic acid on zinc availability. Proc. Soc. Exp. Biol. Med. 103:304–306.[Medline]
Overturf, K., V. Raboy, Z. J. Cheng, and R. W. Hardy. 2003. Mineral availability from barley low phytic acid grains in rainbow trout (Oncorhynchus mykiss) diets. Aquaculture Nutrition 9:239–246.
Potter, L. M., M. Potchanakorn, V. Ravindran, and E. T. Kornegay. 1995. Bioavailability of phosphorus in various phosphate sources using body weight and toe ash as response criteria. Poult. Sci. 74:813–820.[Web of Science][Medline]
Raboy, V. 2001. Seeds for a better future: ‘Low phytate’ grains help to overcome malnutrition and reduce pollution. Trends Plant Sci. 6:458–462.[Web of Science][Medline]
Ravindran, V., W. L. Bryden, and E. T. Kornegay. 1995. Phytates: Occurrence, bioavailability and implications in poultry nutrition. Poult. Avian Biol. Rev. 6:125–143.
SAS. 1996. Statistics. In SAS User’s Guide, 1996 ed. SAS Institute, Cary, NC.
Sugiura, S. H., V. Raboy, K. A. Young, F. M. Dong, and R. W. Hardy. 1999. Availability of phosphorus and trace minerals in low-phytate varieties of barley and corn for rainbow trout (Oncorhynchus mykiss). Aquaculture 170:285–296.
Thiel, U., and E. Weigand. 1992. Influence of dietary zinc and microbial phytase supplementation on zinc retention and zinc excretion in broiler chicks. Page 460 in Proc. World’s Poult. Congr. Vol. 3. World’s Poult. Sci. Assoc., Amsterdam, the Netherlands.
Veum, T. L., D. R. Ledoux, V. Raboy, and D. S. Ertl. 2001. Low-phytic acid corn improves nutrient utilization for growing pigs. J. Anim. Sci. 79:2873–2880.
Wada, L., J. R. Turnland, and J. C. King. 1985. Zinc utilization in young men fed adequate and low zinc intakes. J. Nutr. 115:1345–1354.
Waldroup, P. W., J. H. Kersey, E. A. Saleh, C. A. Fritts, F. Yan, H. L. Stilborn, R. C. Crum, Jr., and V. Raboy. 2000. Non-phytate phosphorus requirements and phosphorus excretion of broiler chicks fed diets composed of normal or high available phosphate corn with and without microbial phytase. Poult. Sci. 79:1451–1459.
Yan, F., J. H. Kersey, C. A. Fritts, P. W. Waldrup, H. L. Stilborn, R. C. Crum, Jr., D. W. Rice, and V. Raboy. 2000. Evaluation of normal yellow dent corn and high available phosphorus corn in combination with reduced dietary phosphorus and phytase supplementation for broilers grown to market weights in litter pens. Poult. Sci. 79:1282–1289.
Yi, Z., E. T. Kornegay, and D. M. Denbow. 1996. Supplemental microbial phytase improves zinc utilization in broilers. Poult. Sci. 75:540–546.[Web of Science][Medline]
Ziegler, E. E., R. E. Serfass, S. E. Nelson, R. Figueroa-Colon, B. B. Edwards, R. S. Houk, and J. J. Thompson. 1989. Effect of low zinc intake on absorption and excretion of zinc by infants studied with 70Zn as extrinsic tag. J. Nutr. 119:1647–1653.
Zyla, K., D. Gogol, J. Koreleski, S. Swiatkiewicz, and D. R. Ledoux. 1999. Simultaneous application of phytase and xylanase to broiler feeds based on wheat: In vitro measurements of phosphorus and pentose release from wheats and wheat-based feeds. J. Sci. Food Agric. 79:1832–1840.
Zyla, K., M. Czubak, J. Roznowski, and T. Fortuna. 2002. Changes in the activity of endogenous phytase in germinating sesame seeds. Pages 137–138 in Proc. XXXIII Sci. Mtg. Food Chem. Technol. Committee of Polish Acad. Sci., Lublin, Poland.
This article has been cited by other articles:
|
|
 |
|
  T. L. Veum, D. R. Ledoux, M. C. Shannon, and V. Raboy Effect of graded levels of iron, zinc, and copper supplementation in diets with low-phytate or normal barley on growth performance, bone characteristics, hematocrit volume, and zinc and copper balance of young swine1 J Anim Sci, August 1, 2009; 87(8): 2625 - 2634. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
