Nutritional Benefits of Phytase and Dietary Determinants of its Efficacy

A comparison of the release of phosphorus by a phytase enzyme in pigs fed diets deficient or adequate in phosphorus content

Previous research indicated that phytase may release less phosphorus (P) from phytate when it is evaluated using diets with P levels above requirement as compared with diets below requirement. The objectives of this experiment were to further test the hypothesis that the P release values determined for phytase are higher when pigs are fed diets that are deficient (DE) in P compared with when they are fed diets that are adequate (AD) in P, and that phytase will increase the digestibility of dry matter (DM), gross energy (GE), nitrogen (N), and calcium (Ca) independent of dietary P status. Twenty-four barrows (body weight: 23.2 ± 1.8 kg) were randomly assigned to one of eight dietary treatments and housed in individual pens for 21 d and then moved to metabolism crates for 9 d, with the collection of urine and feces occurring on the final 5 d. A basal corn-soybean meal diet (P-AD) was formulated at 0.36% standardized total tract digestible (STTD) P and total calcium:STTD P (Ca:STTD P) of 2:1. A P-DE diet was also formulated to maintain a constant Ca:STTD P of 2:1 in both basal diets. Phytase was added to AD and DE diets at 350, 600, 1,000 phytase units (FYT)/kg. Pig was the experimental unit; diet (P-AD or P-DE), phytase level, and replicate were fixed effects. Orthogonal polynomial contrasts were used to test linear and quadratic effects of phytase within P-AD and P-DE diets. Phytase improved apparent total tract digestibility (ATTD) and STTD of P in both P-AD (linear P < 0.001) and P-DE diets (quadratic P < 0.001). Estimates for STTD P release were 0.07%, 0.09%, and 0.09% for 350, 600, and 1,000 phytase units (FYT)/kg in P-DE diets, and 0.02%, 0.03%, and 0.05% in P-AD diets, respectively. In P-DE diets, phytase improved absorption and retention of P and increased urinary excretion of P (quadratic P < 0.001). In P-AD diets, phytase improved absorption of P (linear P = 0.066), tended to improve retention (linear P = 0.066), and increased urinary excretion of P (quadratic P = 0.021). Phytase improved ATTD of Ca in P-DE diets (quadratic P = 0.002) but not in P-AD diets (P > 0.1). In conclusion, the release of P by phytase is lower in diets that are AD in P than those which are DE. Phytase increased the availability of Ca only in the diets DE in P. Finally, phytase increased the ATTD of DM and tended to increase the ATTD of energy, independent of dietary P status.

Effectiveness of phytase pre-treatment on growth performance, nutrient digestibility and mineral status of common carp (Cyprinus carpio) juveniles fed Moringa by-product based diet

Several anti-nutritional substances are found in plant derivatives for example phytate, that make the nutrients and minerals unavailable to fish, hence leading to poor growth performance. Presence of the anti-nutrient factor such as phytate is a chelated compound and need enzyme for its breakdown and availability of nutrients to improve fish growth. This research work was performed to check the improvement of overall performance of Cyprinus carpio fingerlings by the help of phytase addition in Moringa oleifera by- products based diet. Combination of Moringa seed meal and Moringa leaf meal was utilized as test ingredient to formulate seven test feeds, containing graded levels of phytase (0, 500, 650, 800, 950, 1100 and 1250 FTU kg^-1). In feeding trial of 70 days, fingerlings were given feed two times in a day at the rate of 4% of wet weight of their bodies and faeces were collected. According to current results, it was found that growth performance parameters i.e. weight gain; 25 g, specific growth rate; 1.67 and feed conversion ratio; 1.10 were improved to maximum at 950 FTU kg^-1. Digestibility of nutrients (crude protein; 73%, crude fat; 71% and gross energy; 67%) and minerals absorption was also maximum (Ca; 70%, Zn; 66%, K; 74%, Mn; 66% and P; 71%) at 950 FTU kg^-1. Lowest growth efficiency, nutrient digestibility and mineral absorption were observed in fingerlings fed at control diet (0 FTU kg^-1). Results of the current study, proved that 950 FTU kg^-1 is the most optimum level of phytase to formulate economical and ecofriendly feed for improved growth of C. carpio fingerlings as it decreases the discharge of minerals and nutrients in water bodies.

Design and validation of a real-time PCR technique for assessing the level of inclusion of fungus- and yeast-based additives in feeds

A reliable method for quantification of non-viable microbe-based nutritional and zootechnical additives introduced into feed is essential in order to ensure regulatory compliance, feed safety and product authenticity in industrial applications. In the present work, we developed a novel real-time quantitative polymerase chain reaction (qPCR) -based analysis protocol for monitoring two microbial additives in feed matrices. To evaluate the applicability of the method, pelleted wheat- and maize-based broiler chicken diets containing a non-viable phytase-producing strain of Aspergillus niger produced in solid state fermentation (150 or 300 g/t) and a non-viable selenium-enriched Saccharomyces cerevisiae (100 or 200 g/t) as model feed ingredients, were manufactured and subjected to analysis. Power analysis of the qPCR results indicated that 2 to 6 replicate feed samples were required to distinguish the product doses applied, which confirms that the microbial DNA was efficiently recovered and that potential PCR inhibitors present in the feed material were successfully removed in DNA extraction. The analysis concept described here was shown to be an accurate and sensitive tool for monitoring the inclusion levels of non-viable, unculturable microbial supplements in animal diets.

Mutational analysis of a catalytically important loop containing active site and substrate-binding site in Escherichia coli phytase AppA

A phytase from Escherichia coli, AppA, has been the target of protein engineering to reduce the amount of undigested phosphates from livestock manure by making phosphorous from phytic acid available as a nutrient. To understand the contribution of each amino acid in the active site loop to the AppA activity, alanine and glycine scanning mutagenesis was undertaken. The results of phytase activity assay demonstrated loss of activity by mutations at charged residues within the conserved motif, supporting their importance in catalytic activity. In contrast, both conserved, non-polar residues and non-conserved residues tended to be tolerant to Ala and/or Gly mutations. Correlation analyses of chemical/structural characteristics of each mutation site against mutant activity revealed that the loop residues located closer to the substrate have greater contribution to the activity of AppA. These results may be useful in efficiently engineering AppA to improve its catalytic activity.

Abbreviations: AppA: pH 2.5 acid phosphatase; CSU: contacts of structural units; HAPs: histidine acid phosphatases; SASA: solvent accessible surface area; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SSM: site-saturation mutagenesis; WT: wild type

Modification and application of an in vitro assay to examine inositol phosphate degradation in the digestive tract of poultry

BACKGROUND

An in vitro assay was modified to study the disappearance of inositol hexakisphosphate (InsP₆ ) and the formation of lower inositol phosphate (InsP) isomers in the poultry digestive tract, and three experiments investigated the influence of diets with different ingredients and additives. Using the poultry diet as a matrix, the assay simulated the conditions (e.g. pH, temperature, proteolytic enzymes, water content, and retention time) of the crop, stomach, and small intestine, and extraction and analysis of InsP isomers were immediately conducted.

RESULTS

The assay produced highly reproducible results with coefficients of variation ≤10% for an InsP isomer concentration ≥0.4 µmol g^-1 DM (n = 3), and it was sensitive to the factors that varied in the three experiments.

CONCLUSION

The described assay is a suitable tool that can be used to screen feed enzymes and to investigate the effects of supplements in the absence of endogenous phytases. The ease of handling and high reproducibility of the assay indicated that the assay is a rapid and feasible method that can be used to examine the degradation pathway of phytate in feed under gastrointestinal conditions. © 2017 Society of Chemical Industry.

Molecular advancements in the development of thermostable phytases

Since the discovery of phytic acid in 1903 and phytase in 1907, extensive research has been carried out in the field of phytases, the phytic acid degradatory enzymes. Apart from forming backbone enzyme in the multimillion dollar-based feed industry, phytases extend a multifaceted role in animal nutrition, industries, human physiology, and agriculture. The utilization of phytases in industries is not effectively achieved most often due to the loss of its activity at high temperatures. The growing demand of thermostable phytases with high residual activity could be addressed by the combinatorial use of efficient phytase sources, protein engineering techniques, heterologous expression hosts, or thermoprotective coatings. The progress in phytase research can contribute to its economized production with a simultaneous reduction of various environmental problems such as eutrophication, greenhouse gas emission, and global warming. In the current review, we address the recent advances in the field of various natural as well as recombinant thermotolerant phytases, their significance, and the factors contributing to their thermotolerance.

Microbial enzymes: industrial progress in 21st century

Abstract

Biocatalytic potential of microorganisms have been employed for centuries to produce bread, wine, vinegar and other common products without understanding the biochemical basis of their ingredients. Microbial enzymes have gained interest for their widespread uses in industries and medicine owing to their stability, catalytic activity, and ease of production and optimization than plant and animal enzymes. The use of enzymes in various industries (e.g., food, agriculture, chemicals, and pharmaceuticals) is increasing rapidly due to reduced processing time, low energy input, cost effectiveness, nontoxic and eco-friendly characteristics. Microbial enzymes are capable of degrading toxic chemical compounds of industrial and domestic wastes (phenolic compounds, nitriles, amines etc.) either via degradation or conversion. Here in this review, we highlight and discuss current technical and scientific involvement of microorganisms in enzyme production and their present status in worldwide enzyme market.

Graphical abstract

Improvements in growth performance, bone mineral status and nutrient digestibility in pigs following the dietary inclusion of phytase are accompanied by modifications in intestinal nutrient transporter gene expression

Phytase (PHY) improves growth performance, nutrient digestibility and bone structure in pigs; however, little is known about its effects on intestinal nutrient transporter gene expression. In the present study, a 44 d experiment was carried out using forty-eight pigs (11·76 (sem 0·75) kg) assigned to one of three dietary treatment groups to measure growth performance, coefficient of apparent ileal digestibility (CAID), coefficient of apparent total tract nutrient digestibility (CATTD) and intestinal nutrient transporter gene expression. Dietary treatments during the experimental period were as follows: (1) a high-P (HP) diet containing 3·4 g/kg available P and 7·0 g/kg Ca; (2) a low-P (LP) diet containing 1·9 g/kg available P and 5·9 g/kg Ca; (3) a PHY diet containing LP diet ingredients+1000 phytase units (FTU)/kg of PHY. The PHY diet increased the average daily gain (P< 0·05) and final body weight (P< 0·01) and decreased the feed conversion ratio (P< 0·05) compared with the LP diet. Pigs fed the PHY diet had a higher CAID of gross energy compared with those fed the HP and LP diets (P< 0·001). Pigs fed the PHY diet had increased CAID of P (P< 0·01) and CATTD of Ca and P (P< 0·001) compared with those fed the LP diet. The PHY diet increased the gene expression of the peptide transporter 1 (PEPT1/SLC15A1) (P< 0·05) in the ileum compared with the LP diet. The LP diet decreased the gene expression of the sodium-glucose-linked transporter 1 (SGLT1/SLC5A1) and GLUT2/SLC2A2 (P< 0·05) and increased the expression of membrane Ca channel (TRPV6) and calbindin compared with the HP diet (P< 0·001). In conclusion, feeding a diet supplemented with PHY improves growth performance and nutrient digestibility as well as increases the gene expression of the peptide transporter PEPT1.

Dephytinisation with intrinsic wheat phytase and iron fortification significantly increase iron absorption from fonio (Digitaria exilis) meals in West African women

Low iron and high phytic acid content make fonio based meals a poor source of bioavailable iron. Phytic acid degradation in fonio porridge using whole grain cereals as phytase source and effect on iron bioavailability when added to iron fortified fonio meals were investigated. Grains, nuts and seeds collected in Mali markets were screened for phytic acid and phytase activity. We performed an iron absorption study in Beninese women (n = 16), using non-dephytinised fonio porridge (FFP) and dephytinised fonio porridge (FWFP; 75% fonio-25% wheat), each fortified with ⁵⁷Fe or ⁵⁸Fe labeled FeSO₄. Iron absorption was quantified by measuring the erythrocyte incorporation of stable iron isotopes. Phytic acid varied from 0.39 (bambara nut) to 4.26 g/100 g DM (pumpkin seed), with oilseeds values higher than grains and nuts. Phytase activity ranged from 0.17±1.61 (fonio) to 2.9±1.3 phytase unit (PU) per g (whole wheat). Phytic acid was almost completely degraded in FWFP after 60 min of incubation (pH≈5.0, 50°C). Phytate∶iron molar ratios decreased from 23.7∶1 in FFP to 2.7∶1 in FWFP. Iron fortification further reduced phytate∶iron molar ratio to 1.9∶1 in FFP and 0.3∶1 in FWFP, respectively. Geometric mean (95% CI) iron absorption significantly increased from 2.6% (0.8–7.8) in FFP to 8.3% (3.8–17.9) in FWFP (P<0.0001). Dephytinisation of fonio porridge with intrinsic wheat phytase increased fractional iron absorption 3.2 times, suggesting it could be a possible strategy to decrease PA in cereal-based porridges.

Effect of feed processing and enzyme supplementation on diet digestibility and performance of male weaner pigs fed wheat-based diets in dry or liquid form

One hundred and forty-four individually housed, entire male (Large White × Landrace) weaner pigs (28 days; 7.3 s.d. 0.1 kg) were individually housed and allocated to a 26-day feeding trial of 2 by 2 by 3 factorial design. The factors were (1) feed processing method (meal or steam pelleted), (2) feed form (dry or liquid), and (3) enzyme addition (basal diet, or basal diet plus 300 ppm xylanase or 100 ppm phytase). Five days post weaning, two pigs were removed from each treatment. The basal diet was formulated to be marginally adequate for pigs of this age, providing 13.8 MJ digestible energy (DE)/kg DM and 0.79 g available lysine/MJ DE. The diet contained 0.81% Ca, 0.44% non-phytate-P and 0.31% phytate-P. Compared with pigs fed dry diets, pigs fed liquid diets consumed less feed (70 ± 14.2 g/day; P < 0.05) had a lower daily gain (49 ± 12.5 g/day; P < 0.05) and as a consequence had a lower 26-day weight (1.1 ± 0.4 kg; P < 0.05). However, pigs fed liquid diets had a better feed conversion efficiency (adjusted to the same DM content as dry feed) than pigs on dry diets (1.16 versus 1.20 ± 0.02; P < 0.05). Steam pelleting the diets had no effect on feed intake or daily gain, but did improve feed conversion ratio (1.14 versus 1.22 ± 0.02; P < 0.05). The poorer growth on liquid feeds appeared to result from the feeding method imposing a degree of restriction on feed intake. Xylanase or phytase supplementation did not significantly affect non-starch polysaccharide levels in the diets or growth performance. Phytase supplementation increased (P < 0.05) daily intake, daily gain and 26-day weight, of pigs fed dry diets, but not those fed liquid diets. The results indicated that when diets were fed in liquid form, prior steam pelleting of the diets and enzyme supplementation did not provide additional benefit.

Nutrient utilization and manure P excretion in growing pigs fed corn-barley-soybean based diets supplemented with microbial phytase

The effect of high levels of microbial phytase supplementation in diets for growing pigs was studied in a 2-week performance and nutrient digestibility trial involving 28 growing pigs weighing 16.4 +/- 1.06 (mean +/- SD) kg. Seven corn-barley-soybean meal-based diets consisting of a positive control (PC) formulated to meet or exceed NRC nutrient requirements; a negative control (NC) with non-phytate P reduced by 0.1% unit from NRC requirement and fed without or with 500 or 1000 U/kg; a doubled negative control (DNC) with no added inorganic P and fed without or with 2000 or 4000 U/kg. Chromic oxide was added as an indigestible marker and all diets were fed as mash. Pigs fed the PC diet had a higher P digestibility compared with those fed the NC (P < 0.02) and the DNC (P < 0.001) diets. Supplementing the NC diet with pyhtase tended to improve P digestibility (P < 0.10). However, addition of phytase to the DNC diet resulted in linear (P < 0.001) and quadratic (P < 0.03) increases in P digestibility with an overall improvement of 8% and 121% at 4000 phytase U/kg of diet, respectively, compared with the PC and DNC diets. Apparent total tract digestibility of N, OM and DM were higher (P < 0.05) in the PC diet compared with the DNC diet, but not the NC diet (P < 0.10). No effect of phytase addition to NC was observed on Ca, N, DM and OM digestibility. Phytase addition to the DNC diet resulted in a linear increase (P < 0.05) in N, DM and OM digestibility but not Ca. Increasing the levels of phytase supplementation in the NC and the DNC diets linearly decreased fecal P (P < 0.05) content by 45 and 42%, respectively. Adding phytase at 1000 or 4000 U/kg increased P retention (P < 0.05) by 14.3 or 15.6% units, respectively, compared with the PC diet. Urinary P excretion was higher in the group fed the PC diet compared with those fed the NC and DNC diets (P < 0.05). The results of this study show that complete removal of inorganic P from growing pig diets coupled with phytase supplementation improves digestibility and retention of P and N, thus reducing manure P excretion without any negative effect on pig performance.

Effects of citric acid and microbial phytase on amino acid digestibility in broiler chickens

1. Two experiments with growing chickens were carried out to study the effects of the inclusion of a microbial phytase (Natuphos 5000) and citric acid (CA) in maize-soybean-based diets on the performance and apparent ileal digestibility (AID) of crude protein (CP) and amino acids (AA). In both experiments the diets were formulated to contain the same amounts of energy and protein. 2. In the first experiment, data were analysed as a 2 x 2 factorial arrangement with two concentrations of available phosphorus (AP) from one day to 3 weeks of age (3.5 and 2.2 g/kg) and for 3 to 6 weeks (2.7 and 1.4 g/kg), and two inclusions of commercial phytase (0 and 500 FTU/kg) in each period. The AID of CP and dispensable and indispensable AA were not modified by the AP content of the diet. Addition of phytase improved the AID of CP and dispensable and indispensable AA only at low AP levels. 3. In the second experiment, data were analysed as a 3 x 2 factorial arrangement with three concentrations of citric acid (0, 20 and 50 g/kg) and two inclusions of commercial phytase (0 and 750 FTU/kg). Diets were formulated with deficient contents of AP (2.5 g/kg). Performance was not affected by commercial phytase addition. The addition of CA reduced the weight gain but did not modify the feed intake and gain:feed. In general, the AID of CP and dispensable and indispensable AA were not affected by CA addition. Commercial phytase increased the apparent ileal digestibility of crude protein but had no effect on AID of dispensable and indispensable AA. 4. In conclusion, the present work showed that microbial phytase enhanced AA digestibility in maize-soy-based diet only at very low AP concentrations, and that CA had no affect on the AID of CP and dispensable and indispensable AA. No synergism between CA and microbial phytase was detected.

Supplemental Escherichia coli phytase and strontium enhance bone strength of young pigs fed a phosphorus-adequate diet

Young pigs represent an excellent model of youth to assess potentials of dietary factors for improving bone structure and function. We conducted 2 experiments to determine whether adding microbial phytase (2,000 U/kg, OptiPhos, JBS United) and Sr (50 mg/kg, SrCO3 Alfa Aesar) into a P-adequate diet further improved bone strength of young pigs. In Expt. 1, 24 gilts (8.6 +/- 0.1 kg body wt) were divided into 2 groups (n = 12), and fed a corn-soybean-meal basal diet (BD, 0.33% available P) or BD + phytase for 6 wk. In Expt. 2, 32 pigs (11.4 +/- 0.2 kg) were divided into 4 groups (n = 8), and fed BD, BD + phytase, BD + Sr, or BD + phytase and Sr for 5 wk. Both supplemental phytase and Sr enhanced (P < 0.05) breaking strengths (11-20%), mineral content (6-15%), and mineral density (6-11%) of metatarsals and femurs. Supplemental phytase also resulted in larger total bone areas (P < 0.05) and a larger cross-sectional area of femur (P = 0.06). Concentrations of Sr were elevated 4-fold (P < 0.001) in both bones by Sr, and moderately increased (P = 0.05-0.07) in metatarsal by phytase. In conclusion, supplemental phytase at 2000 U/kg of P-adequate diets enhanced bone mechanical function of weanling pigs by modulating both geometrical and chemical properties of bone. The similar benefit of supplemental Sr was mainly due to an effect on bone chemical properties.

Alkaline phytase from Lilium longiflorum: Purification and structural characterization

Phytases catalyze the hydrolysis of phytic acid (myo-inositol hexakisphosphate), the most abundant inositol phosphate in cells. Phytases are of great commercial importance because their use as food and animal feed supplement has been approved by many countries to alleviate environmental and nutritional problems. Although acid phytases have been extensively studied, information regarding alkaline phytases is limited. Alkaline phytases with unique catalytic properties have been identified in plants, however, there is no report on the purification or structural properties. In this paper, we describe the purification of alkaline phytase from plant tissue. The purification was challenging because of contamination from non-specific phosphatases and acid phytases and low endogenous concentration. The purification of alkaline phytase from pollen grains of Lilium longiflorum involved selective precipitation by heat and ammonium sulfate followed by anion exchange and chromatofocusing chromatography and, finally, gel electrophoresis. Alkaline phytase was purified approximately 3000-fold with an overall recovery of 4.2%. The native molecular mass was estimated to be in the range of 118+/-7 kDa by Ferguson plot analysis and Mr of denatured protein in the range of 52-55 kDa by SDS-PAGE suggesting that the enzyme is a homodimer. Separation by 2-D gel and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometric analysis of separated proteins indicates the presence of multiple mass and charge isoforms with pI values between 7.3 and 8.3. To our knowledge, this is the first alkaline phytase to be purified from plant sources. The unique properties suggest that the enzyme has the potential to be useful as a feed and food supplement.

Alkaline phytase from lily pollen: Investigation of biochemical properties

Phytases catalyze the hydrolysis of phytic acid (InsP6, myo-inositol hexakisphosphate), the most abundant inositol phosphate in cells. In cereal grains and legumes, it constitutes 3-5% of the dry weight of seeds. The inability of humans and monogastric animals such as swine and poultry to absorb complexed InsP6 has led to nutritional and environmental problems. The efficacy of supplemental phytases to address these issues is well established; thus, there is a need for phytases with a range of biochemical and biophysical properties for numerous applications. An alkaline phytase that shows unique catalytic properties was isolated from plant tissues. In this paper, we report on the biochemical properties of an alkaline phytase from pollen grains of Lilium longiflorum. The enzyme exhibits narrow substrate specificity, it hydrolyzed InsP6 and para-nitrophenyl phosphate (pNPP). Alkaline phytase followed Michaelis-Menten kinetics with a K(m) of 81 microM and V(max) of 217 nmol Pi/min/mg with InsP6 and a K(m) of 372 microM and V(max) of 1272 nmol Pi/min/mg with pNPP. The pH optimum was 8.0 with InsP6 as the substrate and 7.0 with pNPP. Alkaline phytase was activated by calcium and inactivated by ethylenediaminetetraacetic acid; however, the enzyme retained a low level of activity even in Ca2+-free medium. Fluoride as well as myo-inositol hexasulfate did not have any inhibitory affect, whereas vanadate inhibited the enzyme. The enzyme was activated by sodium chloride and potassium chloride and inactivated by magnesium chloride; the activation by salts followed the Hofmeister series. The temperature optimum for hydrolysis is 55 degrees C; the enzyme was stable at 55 degrees C for about 30 min. The enzyme has unique properties that suggest the potential to be useful as a feed supplement.

Industrial enzyme applications

The effective catalytic properties of enzymes have already promoted their introduction into several industrial products and processes. Recent developments in biotechnology, particularly in areas such as protein engineering and directed evolution, have provided important tools for the efficient development of new enzymes. This has resulted in the development of enzymes with improved properties for established technical applications and in the production of new enzymes tailor-made for entirely new areas of application where enzymes have not previously been used.

Effects of microbial phytase supplementation on mineral utilization and serum enzyme activities in broiler chicks fed different levels of phosphorus

An experiment was conducted to study the effect of microbial phytase (Natuphos 500) supplementation in chicks (0 to 6 wk of age) fed different levels of nonphytate phosphorus (nPP) on performance, mineral retention, bone and plasma minerals and serum enzyme activities. Data were analyzed as a 2 x 2 factorial arrangement with two levels of nPP for age periods of 1-d-old to 3 wk (0.35 and 0.22%) and 3 to 6 wk (0.27 and 0.14%) and two levels of phytase (0 and 500 U/kg) in each period. A positive control, adequate in nPP and Ca without phytase, was used. The low-nPP diets caused a negative effect on the performance (P < 0.05) compared to the normalnPP diet. Phytase had a favorable effect on weight gain at 3 wk (P < 0.004) and 6 wk (P < 0.0475) of age and on feed consumption only at 3 wk (P < 0.0106). Feed efficiency was not affected at any stage by addition of phytase. Performances of chicks fed with 0.35 and 0.27% nPP and phytase were comparable to those obtained with the normal-nPP diets. Decreasing nPP content in the diet increased (P < 0.0001) P retention at 3 and 6 wk of age, increased Mg retention at 6 wk, and decreased (P < 0.0001) Ca and Zn retentions at 3 and 6 wk, respectively. Phytase supplementation increased (P < 0.0001) Ca, P, Mg, and Zn retention at 3 and 6 wk of age. Likewise, the decrease in nPP content in the diet caused a significant reduction of tibia ash (P < 0.0023) and Mg content (P < 0.0001) in tibia ash and reduced liver (P < 0.0240), spleen (P < 0.0176), and tibia (P < 0.0001) weights. Similarly, Ca (P < 0.0369) and Zn (P < 0.0181) contents in tibia ash were increased in response to decreasing nPP levels in the diet. Phytase supplementation increased tibia weight (P < 0.0019), tibia ash (P < 0.0021), and Mg (P < 0.0339) and Zn (P < 0.0353) concentrations and reduced (P < 0.0161) the relative liver weight. By decreasing nPP levels in the diet, plasma Ca (P < 0.0001), Mg (P < 0.0001) and Zn (P < 0.0048) concentrations, and alkaline phosphatase (ALP) activity (P < 0.0299) increased, and plasma P content (P < 0.0001), aspartate aminotransferase (AST) activity (P < 0.0001), and total protein (TP) content (P < 0.0050) were reduced. Phytase supplementation increased plasma P level (P < 0.0001) and serum AST activity (P < 0.0049), reduced plasma Ca (P < 0.0001) and Mg (P < 0.0050) contents, and reduced serum alanine aminotransferase (ALT) (P < 0.0048), ALP (P < 0.0001) and lactate dehydrogenase (LDH) (P < 0.0192) activities. Plasma Zn was not affected by phytase supplementation. These results demonstrated that microbial phytase supplementation to low-P diets improved performance; P, Ca, Mg, and Zn use; and tibia weight and relative liver weight in broiler chickens. Likewise, serum AST, ALT, ALP, and LDH activities, as well as TP concentration, were also affected by phytase supplementation.