Performance of Seven Commercial Phytases in an in Vitro Simulation of Poultry Digestive Tract

Determination of phytic acid disappearance, ileal P digestibility at different dietary Ca levels, and relative P bioavailability in soybean meal, canola meal, distillers dried grains with solubles, corn fermented protein, and wheat middlings

Three experiments were conducted to evaluate P utilization in soybean meal (SBM), canola meal (CM), distillers dried grains with solubles (DDGS), corn fermented protein (CFP), and wheat middlings (WM) using different assays. In Experiment 1, phytic acid disappearance (myo-inositol 1,2,3,4,5,6-hexakis; InsP6D) and inositol phosphate disappearance (InsP-PD) were determined using precision-fed cecectomized Leghorn roosters. Roosters were precision-fed 20 to 25 g of SBM, CM, DDGS, CFP, and WM. In Experiment 2, InsP6D, InsP-PD, and standardized ileal digestibility (SID) of P at different Ca levels were determined using ad libitum-fed broiler chickens. Semi-purified cornstarch-dextrose-based diets containing SBM, CM, DDGS, CFP, and WM as the sole source of P were fed. All diets contained 0.21% P and limestone was added at the expense of dextrose to provide 0.30, 0.45, 0.60, and 0.75% Ca. In Experiment 3, P bioavailability relative to KH2PO4 was determined based on tibia bone ash. Experiments contained 5 to 6 replicates per treatment. In Experiment 1 with precision-fed roosters, InsP6D and InsP-PD ranged from 8 to 71% among feedstuffs, with the lowest (P < 0.05) disappearance being observed in SBM. In Experiment 2 with ad libitum-fed chickens, there was a Ca × ingredient interaction (P < 0.05) whereby increasing Ca linearly decreased (P < 0.05) InsP6D, InsP-PD, and SID of P for all feedstuffs, excluding CFP. Estimated P digestibility calculated using InsP6D in Experiment 1 was in good agreement with SID in Experiment 2 determined at 0.75% Ca, except for SBM. In Experiment 3, regression of bone ash content (mg/tibia) on supplemental P intake yielded P bioavailability values ranging from 30 to 81% among feedstuffs relative to KH2PO4, with the highest (P < 0.05) bioavailability being observed for DDGS and CFP. In conclusion, 1) InsP6D in precision-fed roosters can provide preliminary indications of P digestibility in plant-based feedstuffs, 2) SID determined at 0.75% Ca was in good agreement with other bioassays, and 3) P in DDGS and CFP was highly available compared with other feedstuffs.

Toxicokinetics of selenate in earthworm sub-tissues and potential bio-accessibility assessment of earthworm-derived selenium

Selenium (Se) pollution is mainly caused by anthropogenic activities, and the resulting biosecurity concerns have garnered significant attention in recent years. Using one-compartmental toxicokinetic (TK) modelling, this study explored the kinetic absorption, sub-tissue distribution, and elimination processes of the main Se species (selenate, Se(VI)) in the cultivated aerobic soil of the earthworm Eisenia fetida. The bio-accessibility of earthworm-derived Se was assessed using an in vitro simulated gastrointestinal digestion test to evaluate its potential trophic risk. The results demonstrated that Se accumulated in the pre-clitellum (PC) and total tissues (TT) of earthworms in a time- and dose-dependent manner. The highest Se levels in the PC, post-clitellum (PoC), and TT were 70.54, 57.93, and 64.26 mg/kg during the uptake phase, respectively. The kinetic Se contents in the earthworms PC and TT were consistent with the TK model but not with PoC. The earthworm TT exhibited a faster uptake (Kus = 0.83-1.02 mg/kg/day) and elimination rate of Se (Kee = 0.044-0.049 mg/kg/day), as well as a shorter half-life time (LT1/2 = 15.88-14.22 days) than PC at low soil Se levels (≤5 mg/kg). Conversely, the opposite trend was observed with higher Se concentrations (10 and 20 mg/kg). These results are likely attributable to the tissue specificity and concentration of the toxicant. Earthworms PC and TT exhibited a higher kinetic Se accumulation factor (BAFk) than steady-state BAF (BAFss), with values ranging from 8 to 24 and 3-13, respectively. Furthermore, the bio-accessibility of earthworm-derived Se to poultry ranged from 66.25 % to 84.35 %. As earthworms are at the bottom of the terrestrial food chain, the high bio-accessibility of earthworm-derived Se poses a potential risk to predators. This study offers data support and a theoretical foundation for understanding the biological footprint of soil Se and its toxicological impacts and ecological hazards.

Modeling the influence of propionic acid concentration and pH on the kinetics of Salmonella Typhimurium

Salmonella Typhimurium is a foodborne pathogen often found in the poultry production chain. Antibiotics have been used to reduce S. Typhimurium contamination in poultry aviaries and improve chicken growth. However, antibiotics were banned in several countries. Alternatively, organic acids, such as propionic acid (PA), can control pathogens. This study determined the PA minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and mathematically modeled S. Typhimurium growth/inactivation kinetics under the influence of PA at different pH values (4.5, 5.5, and 6.5) which are within the pH range of the chicken gastrointestinal tract. The PA MIC against S. Typhimurium was pH-dependent, resulting in 5.0, 3.5 and 9.0 mM undissociated PA at pH 4.5, 5.5, and 6.5, respectively. The Baranyi and Roberts and the Weibull model fit growth and inactivation data well, respectively. Secondary models were proposed. The validated model predicted 3-log reduction of S. Typhimurium in 3 h at 68.2 mM of undissociated PA and pH 4.5. The models presented a good capacity to describe the kinetics of S. Typhimurium subjected to PA, representing a useful tool to predict PA antibacterial action depending on the pH.

Surface Engineering of Escherichia coli to Display Its Phytase (AppA) and Functional Analysis of Enzyme Activities

Escherichia coli phytase (AppA) is widely used as an exogenous enzyme in monogastric animal feed mainly because of its ability to degrade phytic acid or its salt (phytate), a natural source of phosphorus. Currently, successful recombinant production of soluble AppA has been achieved by gene overexpression using both bacterial and yeast systems. However, some methods for the biomembrane immobilization of phytases (including AppA), such as surface display on yeast cells and bacterial spores, have been investigated to avoid expensive enzyme purification processes. This study explored a homologous protein production approach for displaying AppA on the cell surface of E. coli by engineering its outer membrane (OM) for extracellular expression. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of total bacterial lysates and immunofluorescence microscopy of non-permeabilized cells revealed protein expression, whereas activity assays using whole cells or OM fractions indicated functional enzyme display, as evidenced by consistent hydrolytic rates on typical substrates (i.e., p-nitrophenyl phosphate and phytic acid). Furthermore, the in vitro results obtained using a simple method to simulate the gastrointestinal tract of poultry suggest that the whole-cell biocatalyst has potential as a feed additive. Overall, our findings support the notion that biomembrane-immobilized enzymes are reliable for the hydrolysis of poorly digestible substrates relevant to animal nutrition.

Research Note: Evaluation of phytic acid disappearance, ileal P digestibility, and total tract P retention in canola meal supplemented with increasing levels of exogenous phytase using conventional and cecectomized precision-fed roosters and growing chicks

Apparent ileal digestibility (AID) of P, apparent total tract retention (ATTR) of P, and phytic acid disappearance in canola meal were evaluated in the presence of increasing levels of exogenous phytase. In Experiment 1, a precision-fed rooster assay was used to determine phytic acid (myo-inositol 1,2,3,4,5,6-hexakis; InsP6) and inositol phosphate (InsP6-3; InsP-P) disappearance in conventional and cecectomized Leghorn roosters. Roosters were crop intubated with 25 g of canola meal mixed with 0, 500, 1,000, or 2,000 FTU/kg of exogenous phytase. In Experiment 2, InsP6 and InsP-P disappearance and AID and ATTR of P were determined using ad libitum-fed broiler chickens. Treatments consisted of semi-purified diets containing 45% canola meal as the sole source of P. Phytase was added to increase phytase activity by 0, 500, 1,000, or 2,000 FTU/kg. Experiments contained 6 replicates per treatment. Canola meal contained a high phytase activity (1,630 FTU/kg as-fed) due to contamination with a commercially available phytase at the feed mill from which the canola meal was sourced. In Experiment 1 with precision-fed roosters, there was no effect (P > 0.05) of phytase or bird type on InsP6 and InsP-P disappearance; however, phytase linearly reduced (P < 0.05) InsP3 concentrations in excreta. In Experiment 2 with ad libitum-fed chickens, phytase linearly increased (P < 0.05) ileal InsP6 and InsP-P disappearance, and phytase had a quadratic effect (P < 0.05) on excreta InsP6 and InsP-P disappearance. Increasing dietary phytase activity resulted in a linear increase (P < 0.05) in AID of P and phytase had a quadratic effect (P < 0.05) on ATTR of P. In conclusion, titration of high levels of phytase (1,600 to 3,600 FTU/kg as-fed) reduced InsP3 concentrations in precision-fed roosters but did not affect overall phytic acid hydrolysis, which was 78% or greater for all treatments; however, increasing the total phytase activity from 700 to 2,700 FTU in ad libitum-fed broiler chickens increased phytic acid disappearance and P digestibility.

Improving the thermal stability of phytase using core-shell hydrogel beads

A core-shell hydrogel bead system was designed to maintain the catalytic activity of phytase and protect its enzymatic functionality from heat treatment. The designed structure consists of a chitosan-phytase complex core and an alginate-carrageenan hydrogel shell. The core-shell hydrogel was optimized to improve phytase encapsulation efficiency and increase the thermal stability of the encapsulated phytase. After heat treatment, encapsulated phytase retained ∼ 70 % of its catalytic activity and the same secondary structure of free phytase. Fourier transform infrared spectroscopy indicated strong intermolecular interactions between chitosan and phytase in the core, but little interaction between the core and the alginate and κ-carrageenan shell, this supports the structural and functional stability of the phytase. Differential scanning calorimetry confirmed that the designed core-shell structure had a higher melting point. Encapsulating phytase in a core-shell hydrogel bead can enhance the thermal stability of phytase, which broadens the potential applications for phytase delivery.

Interactions of zinc with phytate and phytase in the digestive tract of poultry and pigs: a review

Phytase supplementation is gaining importance in animal nutrition because of its effect on phosphorus (P) digestibility and the increasing relevance of P for sustainable production. The potential inhibitors of phytase efficacy and phytate degradation, such as calcium (Ca) and zinc (Zn), have been a subject of intense research. This review focuses on the interactions of Zn with phytate and phytase in the digestive tract of poultry and pigs, with an emphasis on the effects of Zn supplementation on phytase efficacy and P digestibility. In vitro studies have shown the inhibitory effect of Zn on phytase efficacy. However, relevant in vivo studies are scarce and do not show consistent results for poultry and pigs. The results could be influenced by different factors, such as diet composition, amount of Zn supplement, mineral concentrations, and phytase supplementation, which limit the comparability of studies. The chosen response criteria to measure phytase efficacy, which is mainly tibia ash, could also influence the results. Compared to poultry, the literature findings are somewhat more conclusive in pigs, where pharmacological Zn doses (≥ 1000 mg kg-1 Zn) appear to reduce P digestibility. To appropriately evaluate the effects of non-pharmacological Zn doses, further studies are needed that provide comprehensive information on their experimental setup and include measurements of gastrointestinal phytate degradation to better understand the mechanisms associated with Zn and phytase supplements. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Application of enzyme matrix values for energy and nutrients to a wheat-corn-soybean meal-based broiler diet supplemented with a novel phytase, with or without a xylanase-β-glucanase, achieved a production benefit over a nutritionally adequate unsupplemented diet

The effect of applying an energy and nutrient matrix to a wheat-corn-soybean meal-based diet supplemented with a novel consensus bacterial 6-phytase variant (PhyG) and xylanase-β-glucanase on growth performance, bone mineralization, carcass weights, feed costs, and carbon footprint was evaluated. A randomized complete block design (3,300 Ross 308 mixed-sex birds; 60 pens, 12 pens per treatment) tested 5 treatments: 1) a positive control diet (PC), containing 0.92, 0.84, 0.71% Ca and 0.43, 0.38, 0.30% digestible P during 1 to 10, 11 to 21, and 22 to 32 d of age, respectively; 2) a negative control reduced in Ca, digestible P, digestible AA, ME, and Na by phase based on the PhyG dosing regimen (NC1); 3) NC1 supplemented with PhyG at 2,000, 1,500, and 1,000 FTU/kg by phase (NC1+PhyG); 4) as NC1 but additionally reduced in ME (NC2); and 5) NC2 supplemented with PhyG as in 3) plus 1,220 U/kg of xylanase and 152 U/kg of β-glucanase (NC2+PhyG+XB). Final (d 32) BW, overall (0-32 d of age) ADFI, FCR, d 10 and 32 tibia ash and carcass part weights were reduced or impaired (P < 0.05) in NC1 and NC2 vs. PC (d 32 BW -477 g/bird (23.4%) and -422 g/bird (20.7%), respectively). Growth performance (all measures, all phases) was improved and tibia ash (at 10 and 32 d of age), total carcass thigh, breast and leg weights were increased (P < 0.05) in NC1+PhyG vs. NC1, and NC2+PhyG+XB vs. NC2. Overall growth performance outcomes in NC1+PhyG and NC2+PhyG+XB were not different (P > 0.05) from the PC. Total feed cost and carbon footprint per kilogram BW gain (BWG) were reduced (P < 0.05) vs. PC in NC2+PhyG+XB [-0.052 € and -376 g CO2 eq./kg BWG, respectively] and NC1+PhyG [-0.038 € and -260 g CO2 eq./kg BWG, respectively]. The results validated the nutrient matrices in the test diets and highlighted a potential feed cost and environmental sustainability benefit which was greatest when the enzymes were applied in combination.

Microbial Phytases: Properties and Applications in the Food Industry

Microbial phytases are enzymes that break down phytic acid, an anti-nutritional compound found in plant-based foods. These enzymes which are derived from bacteria and fungi have diverse properties and can function under different pH and temperature conditions. Their ability to convert phytic acid into inositol and inorganic phosphate makes them valuable in food processing. The application of microbial phytases in the food industry has several advantages. Firstly, adding them to animal feedstuff improves phosphorus availability, leading to improved nutrient utilization and growth in animals. This also reduces environmental pollution by phosphorus from animal waste. Secondly, microbial phytases enhance mineral bioavailability and nutrient assimilation in plant-based food products, counteracting the negative effects of phytic acid on human health. They can also improve the taste and functional properties of food and release bioactive compounds that have beneficial health effects. To effectively use microbial phytases in the food industry, factors like enzyme production, purification, and immobilization techniques are important. Genetic engineering and protein engineering have enabled the development of phytases with improved properties such as enhanced stability, substrate specificity, and resistance to degradation. This review provides an overview of the properties and function of phytases, the microbial strains that produce them, and their industrial applications, focusing on new approaches.

Comparison of mucosal phosphatase activity, phytate degradation, and nutrient digestibility in 3-week-old turkeys and broilers at different dietary levels of phosphorus and phytase

A comparison between 3-wk-old female turkeys (B.U.T. 6) and broilers (Ross 308) was performed to study the effects of species, dietary P, Ca, and phytase levels on gut mucosal phosphatase activity, myo-inositol hexakisphosphate (InsP6) degradation along the digestive tract, digestibility of P, Ca, and amino acids, and concentrations of myo-inositol in the digesta and blood. The experimental diets were corn-soybean meal-based and identical for both species. Two dietary P and Ca concentrations (CaP-: 4.1 g P/kg, 5.5 g Ca/kg and CaP+: 9.0 g P/kg, 12.0 g Ca/kg) and 2 levels of phytase supplementation (0 and 1,500 FTU/kg) were used in a 2 × 2 factorial design and fed to the animals for 7 d in their third week of age. Each diet was randomly assigned to 6 broiler and 6 turkey pens, with 10 birds each. After slaughter, blood, digesta from the crop, gizzard, duodenum, lower ileum, and mucosa from the jejunum were collected. When fed CaP- without phytase supplementation, there were no differences between species in gut mucosal phosphatase activity, prececal InsP6 disappearance, and P and Ca digestibility, indicating a similar intrinsic capacity for phytate degradation in both species. When fed CaP+ without phytase supplementation, turkeys showed higher prececal InsP6 disappearance than broilers. Phytase supplementation increased prececal InsP6 disappearance and digestibility of P and Ca in both species. However, the phytase-induced increase in prececal InsP6 disappearance was more pronounced in broilers than in turkeys, possibly due to more adequate conditions for phytase activity in the broiler crop. In broilers, phytase supplementation increased amino acid digestibility overall, whereas, in turkeys, it increased with CaP+ and decreased with CaP-. In addition, the relationship between myo-inositol concentration in the ileum and blood differed between species, indicating differences in myo-inositol metabolism. It was concluded that 3-week-old turkeys and broilers differ in nutrient digestibility and InsP degradation in some segments of the digestive tract but have similar endogenous InsP6 degradation when fed low P and Ca diets.

An In Vitro Model of the Chicken Gastrointestinal Tract with Special Emphasis to the Cecal Microbiota

An in vitro model of the upper gastrointestinal tract as well as the chicken cecum was developed to have a predictive tool for estimating the production performance of animals by analyzing the feeding value of a certain diet. The upper gastrointestinal tract consists of a batch type model, whereas the cecal model is comprised of 4 semi-continuous connected vessels inoculated with cecal or fecal microbes. The upper gastrointestinal tract and cecal simulations were both run with a corn- and a wheat-based diet to simulate 2 typical feed types. Samples were collected after the 5-h cecal simulations and aliquots were frozen to assess inoculum stability. The microbiota was analyzed by 16S rRNA gene sequencing, whereas short chain fatty acids as microbial metabolites were analyzed by using gas chromatography. As expected, some significant differences in microbial abundance after simulation between the cecal and fecal slurry samples (P = 0.001) were detected, as well between the fresh and frozen status (P = 0.001), hence simulations inoculated with cecal and fresh samples being more diverse. For the measured metabolites, almost all of them increased (P < 0.05) significantly when comparing fresh and frozen inoculum. The present chicken intestinal in vitro model represents a rapid systematic screening system for studying dietary related microbial changes and reducing the need of animal sacrifice for experimentation.

The Contribution of Phytate-Degrading Enzymes to Chicken-Meat Production

The contribution that exogenous phytases have made towards sustainable chicken-meat production over the past two decades has been unequivocally immense. Initially, their acceptance by the global industry was negligible, but today, exogenous phytases are routine additions to broiler diets, very often at elevated inclusion levels. The genesis of this remarkable development is based on the capacity of phytases to enhance phosphorus (P) utilization, thereby reducing P excretion. This was amplified by an expanding appreciation of the powerful anti-nutritive properties of the substrate, phytate (myo-inositol hexaphosphate; IP₆), which is invariably present in all plant-sourced feedstuffs and practical broiler diets. The surprisingly broad spectra of anti-nutritive properties harbored by dietary phytate are counteracted by exogenous phytases via the hydrolysis of phytate and the positive consequences of phytate degradation. Phytases enhance the utilization of minerals, including phosphorus, sodium, and calcium, the protein digestion, and the intestinal uptakes of amino acids and glucose to varying extents. The liberation of phytate-bound phosphorus (P) by phytase is fundamental; however, the impacts of phytase on protein digestion, the intestinal uptakes of amino acids, and the apparent amino acid digestibility coefficients are intriguing and important. Numerous factors are involved, but it appears that phytases have positive impacts on the initiation of protein digestion by pepsin. This extends to promoting the intestinal uptakes of amino acids stemming from the enhanced uptakes of monomeric amino acids via Na⁺-dependent transporters and, arguably more importantly, from the enhanced uptakes of oligopeptides via PepT-1, which is functionally dependent on the Na⁺/H⁺ exchanger, NHE. Our comprehension of the phytate-phytase axis in poultry nutrition has expanded over the past 30 years; this has promoted the extraordinary surge in acceptance of exogenous phytases, coupled with the development of more efficacious preparations in combination with the deflating inclusion costs for exogenous phytases. The purpose of this paper is to review the progress that has been made with phytate-degrading enzymes since their introduction in 1991 and the underlying mechanisms driving their positive contribution to chicken-meat production now and into the future.

Mucosal phosphatase activity, phytate degradation, and mineral digestibility in 6-week-old turkeys and broilers at different dietary levels of phosphorus and phytase and comparison with 3-week-old animals

Female turkeys (B.U.T. 6) and broilers (Ross 308) were compared at 6 wk of age to evaluate the effects of species, dietary P, Ca, and phytase levels on myo-inositol hexakisphosphate (InsP₆) degradation along the digestive tract, gut mucosal phosphatase activity, P and Ca digestibility, and myo-inositol concentrations in the digesta and blood. The environmental conditions and experimental corn-soybean meal-based diets were the same for both species. Four diets with either combination of 2 levels of P and Ca (CaP-: 4.0 g P/kg, 5.4 g Ca/kg and CaP+: 6.0 g P/kg, 8.0 g Ca/kg) and 2 levels of phytase supplementation (0 and 1,500 FTU/kg) were fed to the animals for 7 d at their sixth wk of age. Each diet was randomly assigned to 6 pens per species, with 10 birds each. After slaughter, blood, digesta from the crop, gizzard, duodenum, lower ileum, and jejunal mucosa were collected. Endogenous mucosal phosphatase activity in the jejunum was higher in turkeys than in broilers. Prececal InsP₆ disappearance was also higher in turkeys than in broilers when phytase was not supplemented. Phytase supplementation led to a higher prececal InsP₆ disappearance in broilers than in turkeys, likely due to different crop conditions such as moisture content. However, prececal P digestibility was higher in turkeys than broilers. Different relationships between myo-inositol concentration in the ileum digesta and blood were found, depending on the species. A comparison of the results with those obtained in 3-wk-old birds of a companion study showed that in diets with low Ca and P levels, prececal InsP₆ disappearance increased with age in turkeys, but not in broilers. This coincided with changes in the conditions of the digestive tract, such as the water content in the crop, gizzard pH, and mucosal phosphatase activity. In conclusion, occurrence of differences in phytate degradation between turkeys and broilers, fed the same feed, depended on age and can be explained by different physiological development of the digestive tract.

Artificial gut and the applications in poultry: A review

Artificial gut models including both the gastric and intestinal phases have been used in poultry research for decades to predict the digestibility of nutrients, the efficacy of feed enzymes and additives, and caecal fermentation. However, the models used in the past are static and cannot be used to predict interactions between the feed, gut environment and microbiome. It is imperative that a standard artificial gut model for poultry is established, to enable these interactions to be examined without continual reliance on animals. To ensure the validity of an artificial model, it should be validated with in vivo studies. This review describes current practices in the use of artificial guts in research, their importance in poultry nutrition studies and highlights an opportunity to develop a dynamic gut model for poultry to reduce the number of in vivo experiments.

Modeling improvements in ileal digestible amino acids by a novel consensus bacterial 6-phytase variant in broilers

Data from 13 datasets from 4 trials on the effect of a novel consensus bacterial 6-phytase variant (PhyG) on the apparent ileal digestibility (AID) of amino acids (AA) in broilers were used to model AID AA responses. The datasets were obtained from 3 trial locations (New Zealand, Australia and United States) and collectively incorporated variations in diet composition (feedstuff composition, phytate-P (PP) level, limestone solubility), feed form (mash or pellet), bird genetics (strain), and age at sampling (11-35 d of age). In total, 384 observations were analyzed. First, the relationships between AID of AA (as coefficients) and increasing phytase dose level from 0 to 4,000 FTU/kg were evaluated across all datasets using exponential curve fitting. Second, the percentage unit change in AID of AA at each phytase dose level from baseline (basal diet [BD] without phytase) was calculated separately for each dataset and the data then modeled together using exponential curve fitting. The model-predicted mean coefficient of AID of total AA in basal diets was 0.76 (range 0.56 [Cys] to 0.83 [Glu]), which was increased by PhyG to 0.80 and 0.81 at 2,000 and 4,000 FTU/kg, respectively. Exponential increases in the percentage unit improvement in AID of 18 individual and of total AA with increasing phytase dose level were evident (P < 0.05). Improvements (vs. BD) at 2,000 FTU/kg and 4,000 FTU/kg, respectively, were greatest for Cys (+9.2 and +11.0% units), Met (after deduction of synthetic Met, +8.4 and +9.0% units), and Thr (after deduction of synthetic Thr, +6.2 and +7.3% units). The data demonstrated consistent improvements in the AID of AA by the phytase. The modeling results generated from data gathered from birds sampled at different ages and from different dietary settings with correction of synthetic AA for Lys, Met, Thr, and Trp, enabled a more accurate prediction of the digestible AA contribution from the diet by this novel phytase. This will allow diet-specific AA matrix recommendations to be made in commercial feed formulations.

Assessment of crop usage in ad libitum fed birds and short-term phytase efficiency as affected by acid addition

1. A field assessment was performed to map the extent of crop usage and thus retention time in broiler chickens. In addition, a broiler experiment was carried out to study the short-term effect of acid addition on phytase efficacy in the crop.2. In the field assessment, the crop content of 40 ad libitum fed broiler chickens from four different farms were sampled at 10, 20 and 30 d of age. The dry matter (DM) content varied from zero to 32 g.3. From 11 d of age, 120 individually caged chickens were intermittently fed a high phytate-P diet with either no addition or 500 FYT C. braakii-derived phytase added or both phytase and 1.4 % formic acid added. Excreta were collected for assessment of phosphorus (P) retention. At 20 and 21 d of age, starved birds were fed for 1 h, and thereafter crop and gizzard contents were collected every 20 min until 140 min after start of the feeding. At 60 and 140 min, the contents from the jejunum and ileum were collected.4. All diets reduced the concentration of phytate in the crop, however the combination of acid and phytase resulted in a higher degradation (P<0.05) than the other diets from 20 min after the start of feeding. Simultaneously, the concentration of the smaller inositol phosphate isomers, such as inositol-5-phosphate, increased (P<0.05). Phytase increased (P<0.05) P retention, and the combination of acid and phytase increased jejunal P digestibility (P<0.05) compared to the other diets.5. The results indicated that lower pH in the crop due to acid addition improved phytase efficacy and increased P digestibility in the anterior digestive tract, even with short retention times.

Dietary Phosphorus and Calcium Utilization in Growing Pigs: Requirements and Improvements

The sustainability of animal production relies on the judicious use of phosphorus (P). Phosphate, the mined source of agricultural phosphorus supplements, is a non-renewable resource, but phosphorus is essential for animal growth, health, and well-being. P must be provided by efficient and sustainable means that minimize the phosphorus footprint of livestock production by developing precise assessment of the bioavailability of dietary P using robust models. About 60% of the phosphorus in an animal's body occurs in bone at a fixed ratio with calcium (Ca) and the rest is found in muscle. The P and Ca requirements must be estimated together; they cannot be dissociated. While precise assessment of P and Ca requirements is important for animal well-being, it can also help to mitigate the environmental effects of pig farming. These strategies refer to multicriteria approaches of modeling, efficient use of the new generations of phytase, depletion and repletion strategies to prime the animal to be more efficient, and finally combining these strategies into a precision feeding model that provides daily tailored diets for individuals. The industry will need to use strategies such as these to ensure a sustainable plant-animal-soil system and an efficient P cycle.

Effect of increasing dose level of a novel consensus bacterial 6-phytase variant on phytate degradation in broilers fed diets containing varied phytate levels

1. The effect of increasing the dose level of a novel consensus bacterial 6-phytase variant on apparent ileal digestibility (AID) of phosphorus (P), phytic acid (inositol hexa-phosphate, IP₆) and ileal IP₆ degradation profile was studied in diets containing varying phytate-P (PP) levels.2. Ross 308, one-day-old males (n=1,800) were allocated to cages (20 birds/cage, six cages/treatment) in a completely randomised design employing a 3 × 5 factorial arrangement (three PP levels: 2.45 (low) 2.95 (medium) and 3.45 g/kg (high); five dose levels of phytase (PhyG): 0, 500, 1,000, 2,000 and 4,000 FTU/kg). Phased diets were based on wheat, corn, soybean meal, rapeseed meal and rice bran (d 0 to 10; 2.60 g/kg digestible P, 7.6 g/kg calcium (Ca); d 11 to 21; 2.10 g/kg digestible P, 6.4 g/kg Ca). Ileal digesta was collected on d 21 for determination of P, IP₆ and IP-esters content. Data were analysed by factorial ANOVA; means separation was achieved using Tukey's HSD test.3. Increasing PP reduced AID of IP₆ and sum of IP_3-6 (%) (P<0.05) but absolute P-release (g/kg diet) above NC was increased (P<0.05) at high vs. low PP. Increasing phytase dose exponentially increased (P<0.001) AID IP_6, sum of IP_3-6 (%) and digestible IP_3-6-P g/kg diet (P<0.001). AID P was increased but there was an interaction with PP level (P<0.001). Ileal accumulation of IP_5-3-P was universally low with PhyG at ≥1,000 FTU/kg (<0.06 g/100g DM). At 2,000 and 4,000 FTU/kg, AID IP₆ was 97.2, 92.7, 92.6% and 100, 97.2, 97.1%, respectively, at low, medium and high PP. At 2,000 FTU/kg, phytate-P release estimated as the increase (above NC) in ileal digestible sum of IP_3-6-P in the diet was 2.26, 2.59 and 3.10 g/kg in low, medium and high PP, respectively.4. The data demonstrated that the novel phytase was effective in breaking down phytate to low IP-esters in diets with varied PP content but the optimal dose level for maximising P-release may differ in diets with varying PP content.

Toward Precise Nutrient Value of Feed in Growing Pigs: Effect of Meal Size, Frequency and Dietary Fibre on Nutrient Utilisation

Simple Summary

Feed costs are the most important in swine production. Precise determination of nutritional values of pig diets can help reducing feed costs by reducing security margins for nutrients and therefore provide a more sustainable swine production. In commercial farms, pigs have free access to feed and eat with no limitation according to their natural behaviour. In contrast, during digestibility trials, pigs are restricted in their daily intake of feed, which is distributed in a limited number of meals. The number of meals per day and the amount of feed consumed daily can affect the digestibility of the nutrients, the transit time and the metabolism. To reduce feed costs, by-products are frequently added to diets. Most by-products are rich in dietary fibre, which are known to have negative effects on digestibility. Enzymes can be supplemented in the diet to counteract the negative aspects of dietary fibre, but their efficiency can vary depending on the number of meals per day and the amount of feed consumed daily.

Abstract

Nutritional values of ingredients have been and still are the subject of many studies to reduce security margins of nutrients when formulating diets to reduce feed cost. In most studies, pigs are fed a limited amount of feed in a limited number of meals that do not represent how pigs are fed in commercial farm conditions. With free access to feed, pigs follow their intrinsic feeding behaviour. Feed intake is regulated by satiety and satiation signals. Reducing the feed intake level or feeding frequency can affect digestibility and transit time and induce metabolic changes. To reduce feed costs, alternative ingredients that are frequently rich in dietary fibre are added to diets. Fibre acts on the digestion process and transit time by decreasing energy density and causing viscosity. Various analyses of fibre can be realised, and the measured fibre fraction can vary. Exogenous enzymes can be added to counteract the effect of fibre, but digestive tract conditions, influenced by meal size and frequency, can affect the efficiency of supplemented enzymes. In conclusion, the frequency and size of the meals can affect the digestibility of nutrients by modulating gastrointestinal tract conditions (pH and transit time), metabolites (glucose and short-chain fatty acids) and hormones (glucagon-like peptide 1 and peptide tyrosine tyrosine).

A novel phytase from Citrobactergillenii: characterization and expression in Pichia pastoris (Komagataella pastoris)

The phyCg gene encoding a new phytase from Citrobacter gillenii was optimized, synthesized, cloned and expressed in Pichia pastoris. Analysis of the amino acid sequence of the enzyme showed that it belongs to the histidine acid phosphatase family. The amino acid sequence of the PhyCg phytase has the highest homology (73.49%) with a phytase sequence from Citrobacter braakii. The main characteristics for the purified recombinant phytase were established. The optimum pH and temperature were 4.5 and 50°C, respectively. The specific activity of the enzyme was 1577 U/mg. The Michaelis constant (Km) and the maximum reaction rate (Vmax) for sodium phytate were 0.185 mM and 2185 U/mg, respectively. The enzyme showed the pH and trypsin stability and had a high activity over a wide pH range.

Transcriptional responses in jejunum of two layer chicken strains following variations in dietary calcium and phosphorus levels

BACKGROUND

Calcium (Ca) and phosphorus (P) are essential nutrients that are linked to a large array of biological processes. Disturbances in Ca and P homeostasis in chickens are associated with a decline in growth and egg laying performance and environmental burden due to excessive P excretion rates. Improved utilization of minerals in particular of P sources contributes to healthy growth while preserving the finite resource of mineral P and mitigating environmental pollution. In the current study, high performance Lohmann Selected Leghorn (LSL) and Lohmann Brown (LB) hens at peak laying performance were examined to approximate the consequences of variable dietary Ca and P supply. The experimental design comprised four dietary groups with standard or reduced levels of either Ca or P or both (n = 10 birds per treatment group and strain) in order to stimulate intrinsic mechanisms to maintain homeostasis. Jejunal transcriptome profiles and the systemic endocrine regulation of mineral homeostasis were assessed (n = 80).

RESULTS

Endogenous mechanisms to maintain mineral homeostasis in response to variations in the supply of Ca and P were effective in both laying hen strains. However, the LSL and LB appeared to adopt different molecular pathways, as shown by circulating vitamin D levels and strain-specific transcriptome patterns. Responses in LSL indicated altered proliferation rates of intestinal cells as well as adaptive responses at the level of paracellular transport and immunocompetence. Endogenous mechanisms in LB appeared to involve a restructuring of the epithelium, which may allow adaptation of absorption capacity via improved micro-anatomical characteristics.

CONCLUSIONS

The results suggest that LSL and LB hens may exhibit different Ca, P, and vitamin D requirements, which have so far been neglected in the supply recommendations. There is a demand for trial data showing the mechanisms of endogenous factors of Ca and P homeostasis, such as vitamin D, at local and systemic levels in laying hens.

In vitro assays for evaluating phytate degradation in non-ruminants: chances and limitations

The positive effects of phytases on the environment, animal welfare and animal feed costs have resulted in the continuous development and improvement of these enzymes in the non-ruminant feed market. To test the efficacy of these phytases, a large number of experimental animals are necessary, antagonising the animal welfare aspect of these enzymes. In the present review, we summarise the most prominent available in vitro assays for evaluating phytase enzymes and how far they can reduce the number of in vivo experiments. Several in vitro assays exist that differ in their setup, extent and conditions depending on the animal of interest and the research question. With the in vitro assays described, it is not possible to fully replace in vivo trials. However, for the investigation of phytase effects in feedstuffs, the use of an in vitro assay has several advantages. In vitro assays have the potential to be used for ranking feed enzymes and as screening tools. Applying in vitro protocols will result in a reduction in the number of animals or treatments usually necessary for an in vivo trial, thus acting towards the three Rs. © 2020 Society of Chemical Industry.

Limitations of an in vitro model of the poultry digestive tract on the evaluation of the catalytic performance of phytases

BACKGROUND

The study aims to investigate the limitation of a poultry digestive tract model developed by Menezes-Blackburn et al. [J Agric Food Chem 63: 6142-6149 (2015)] on the evaluation of the bioefficacy of phytases.

RESULTS

It was confirmed that the in vitro model does not mimic the in vivo situation in the birds sufficiently well to identify the best phytase product under real conditions, or to draw conclusion on the effect of phytate concentration, phytate source or feed composition on the bioefficacy of phytase. Addition of calcium ion (Ca²⁺ ) up to a concentration of 10 g kg^-1 to the feed substrate, for example, did not affect enzymatic phytate dephosphorylation in the in vitro model in contrast to the observation in poultry.

CONCLUSION

The in vitro approach was shown to be applicable as a complementary tool in the pre-selection of promising phytase candidates, resulting in a reduction in the number of feeding trials in the initial screening phase. © 2020 The Author. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of two phytases at two doses on performance and phytate degradation in broilers during 1-21 days of age

The effect of two microbial phytases at two dose-levels on performance and apparent ileal digestibility (AID) of nutrients in broilers fed European-type diets was studied. A total of 1,200 d-old Ross 308 male broilers were randomly assigned to 5 treatments with 30 birds/pen and 8 pens/treatment. A nutritionally adequate positive control (PC) diet was tested against 4 experimental diets containing reduced total P, retainable P, Ca and Na as per the recommended nutritional contribution for Buttiauxella phytase (Phy B) at 1,000 FTU/kg (-1.87 g/kg, -1.59 g/kg, -1.99 g/kg and -0.4 g/kg vs. PC, respectively). Experimental diets were supplemented with Phy B at 500 FTU/kg or 1,000 FTU/kg, or Citrobacter phytase (Phy C) at 1,000 FTU/kg or 2,000 FTU/kg. Diets were based on corn, soybean meal, rapeseed meal and sunflower meal and formulated by phase (starter 1–10 d, grower 11–21 d) in crumbled or pelleted form. Overall (d 1–21), at 1,000 FTU/kg, birds fed Phy C exhibited lower BWG (-2.7%), FI (-3.4%) and tibia ash (-2.2%) vs. PC (P < 0.05), and reduced BWG (-3.6%), FI (-3.9%) and tibia ash (-1.8%) vs. Phy B (P < 0.05). Phy B at 1,000 FTU/kg and Phy C at 2,000 FTU/kg maintained performance equivalent to the PC. Digestibility of Ca did not differ among phytase treatments but at 1,000 FTU/kg AID P was greater with Phy B than Phy C (72.3% vs. 62.7%, P < 0.05). Ileal phytate (myo-inositol hexakisphosphate, IP6) digestibility was greatest with Phy B at 1,000 FTU/kg which was higher than Phy C at 1,000 FTU/kg (87.6 vs. 60.6%, P < 0.05). The findings indicate a higher phytate degradation rate of Phy B than Phy C at equivalent dose-level and this is correlated to the performance of the broilers.

Effect of different doses of phytase and protein content of soybean meal on growth performance, nutrient digestibility, and bone characteristics of broilers

This study evaluated the effects of high phytase doses and soybean meal (SBM) with different CP content on growth performance, ileal nutrient digestibility, digestible energy, plasmatic myo-inositol, phosphate release in vitro, and bone composition of broiler chickens. One thousand two hundred 1-day-old broilers were distributed in a 2 × 2 completely randomized factorial arrangement, with 2 phytase doses (1,000 and 2,500 phytase units [FYT]/kg of feed) and 2 SBM with different CP concentrations (45 and 47%), totaling 4 treatments with 12 replicates of 25 birds each. The chickens received feed and water ad libitum. Diets were based on corn and SBM, with different inclusions of soybean hull used to dilute the CP content of SBM according to each treatment. The inclusion of 2,500 FYT increased weight gain from 0 to 21 d (P < 0.05), whereas growth performance from 22 to 42 d was not affected, and SBM had no effect on growth performance. At day 21, ileal digestibility of dry matter, ash, and P, and digestible energy were greater in diets with 2,500 FYT/kg (P < 0.05), as well as phosphate in vitro release (P < 0.01) compared to the lower dose. At day 42, diets with SBM 47% CP and 2,500 FYT/kg promoted greater digestibility of dry matter, ash, CP, Ca, P, and digestible energy (P < 0.001), and greater phosphate release (P < 0.05) in comparison to other treatments. myo-inositol level in the plasma at 21 and 42 d was higher with the use of 2,500 FYT compared to 1,000 FYT (P < 0.05). The higher phytase dose increased tibia ash, toe ash, and Seedor Index (P < 0.05) at day 21, and the Ca content in tibia was higher with 2,500 FYT and SBM 47% CP at day 42. In conclusion, higher phytase doses for broilers improve weight gain, myo-inositol provision, and bone mineral composition. Nutrient ileal digestibility can be enhanced by higher phytase doses when in combination with SBM of greater nutritional quality.

Effect of crop retention time and acidification of the feed on phytase efficacy in broiler chickens

1. An in vitro test to study the effect of pH reduction on phytic acid degradation over time for four commercial phytases was conducted. Changing the pH level affected phytate degradation over time differently for the various phytases (P < 0.05).2. The phytase with the largest response of pH reduction in the in vitro test and a feed pH level of 4.5 was chosen for the broiler experiment. The effect of intermittent feeding, addition of 500 FYT C. braakii-derived phytase and 1% formic acid were tested in a 2 x 2 x 2 factorial arrangement. Ten pens containing 10 birds each were fed each of the treatment combinations from 15 to 36 d of age. Ad libitum fed birds had two 4-h dark periods with 2-h light in-between, while intermittently fed birds in addition had restricted access to the feed through except for four 1-h and one 2-h feeding bouts.3. In addition to assessing performance, excreta were collected on a pen basis. The tibia and contents from jejunum and ileum were collected from one bird per pen. In addition, crop contents were collected from the intermittently fed birds 80, 160 and 240 min after the start of feeding.4. Phytase improved performance, ileal and jejunal P digestibility, P retention and tibia ash and P concentration (P < 0.001). Intermittent feeding increased jejunal P digestibility and P retention (P < 0.001), but ileal P digestibility increased only in the intermittently fed birds compared to the ad libitum fed birds without phytase addition (P = 0.025). Acidification increased jejunal P digestibility only in the ad libitum fed birds (P = 0.019). There was a considerable inositol hexakisphosphate degradation into lower isomers in the crop after 80 min for diets with phytase (InsP_{3 and 4}:P < 0.001), and acidification further increased this degradation (InsP₄:P = 0.007). After 160 min retention time, the effect of phytase and acidification was even higher with more significant (P < 0.05) interactions.5. The current data showed that prolonged retention time in the crop combined with feed acidification increased phytase efficacy by improving the phytate degradation.

Reevaluation of Phytase Action Mechanism in Animal Nutrition

The release of phosphorus from phytates occurs via sequential cleavage of phosphate groups. It was believed that, regardless of the properties of phytases, the rate of phytate dephosphorylation is limited by the first cleavage of any phosphate group. The position of the first cleaved-off phosphate group depending on the specificity of phytase. The inhibition of dephosphorylation initiation is not associated with the action mechanism of the enzyme and can be rather due to the insufficient phytase activity or low availability of phytates. The analysis of the transformations in the inositol hexakisphosphate (IP₆)→inositol (I) reaction chain shows that IP₆ dephosphorylation as a whole limits the phosphate group removal from I(1,2,5,6)P₄ (third reaction from the beginning of hydrolysis of phosphate bonds in PA). The lower availability of nutrients in the presence of phytates is not due to action of phytates, but is caused by PA anions (IP_6-3), which bind positively charged metal ions, amino acids, and proteins. The availability of nutrients increases as a result of the decrease in their binding caused by the decrease in the concentration of IP_(6-3) anions under the action of phytases. Phytases added to feeds play a lesser role in the digestion of phytates compared to natural enzymes and complement their action. The concept of extra-phosphoric effect has no scientific justification, since phytases exhibit only the phosphohydrolase activity and are not able to catalyze other reactions.

Snapshots during the catalytic cycle of a histidine acid phytase reveal an induced-fit structural mechanism

Highly engineered phytases, which sequentially hydrolyze the hexakisphosphate ester of inositol known as phytic acid, are routinely added to the feeds of monogastric animals to improve phosphate bioavailability. New phytases are sought as starting points to further optimize the rate and extent of dephosphorylation of phytate in the animal digestive tract. Multiple inositol polyphosphate phosphatases (MINPPs) are clade 2 histidine phosphatases (HP2P) able to carry out the stepwise hydrolysis of phytate. MINPPs are not restricted by a strong positional specificity making them attractive targets for development as feed enzymes. Here, we describe the characterization of a MINPP from the Gram-positive bacterium Bifidobacterium longum (BlMINPP). BlMINPP has a typical HP2P-fold but, unusually, possesses a large α-domain polypeptide insertion relative to other MINPPs. This insertion, termed the U-loop, spans the active site and contributes to substrate specificity pockets underpopulated in other HP2Ps. Mutagenesis of U-loop residues reveals its contribution to enzyme kinetics and thermostability. Moreover, four crystal structures of the protein along the catalytic cycle capture, for the first time in an HP2P, a large ligand-driven α-domain motion essential to allow substrate access to the active site. This motion recruits residues both downstream of a molecular hinge and on the U-loop to participate in specificity subsites, and mutagenesis identified a mobile lysine residue as a key determinant of positional specificity of the enzyme. Taken together, these data provide important new insights to the factors determining stability, substrate recognition, and the structural mechanism of hydrolysis in this industrially important group of enzymes.

Inositol and gradient phytase supplementation in broiler diets during a 6-week production period: 2. Effects on phytate degradation and inositol liberation in gizzard and ileal digesta contents

An experiment was conducted to evaluate effects of dietary phytase and inositol supplementation on phytate degradation in gizzard and ileal digesta contents of broilers from 1 to 43 d of age. One thousand nine hundred and twenty Yield Plus × Ross 708 male chicks were placed in 64 floor pens (30 birds/pen). Each pen received 1 of 8 dietary treatments from 1 to 43 d of age. Treatment 1 was formulated to contain 0.165 and 0.150% lower calcium and phosphorus, respectively, than treatment 7. Treatments 2 to 6 were formulated by adding phytase at 500, 1,500, 4,500, 13,500, and 40,500 phytase units (FTU)/kg, respectively, to treatment 1. Treatment 8 was established by adding inositol to treatment 7 based on the maximum inositol liberation in treatment 6. At 15, 29, and 43 d of age, gizzard contents, ileal digesta, and blood were collected for analysis of inositol and inositol phosphate (IP) 2, 3, 4, 5, and 6 concentrations. Increasing phytase from 0 to 40,500 FTU/kg resulted in log-quadratic reductions (P < 0.01) of inositol pentaphosphate and inositol hexakisphosphate concentrations in the gizzard and ileal digesta contents of broilers at 15, 29, and 43 d of age. The increase in phytase doses in treatments 1 to 6 reduced IP3 and IP4 concentrations in a log-quadratic manner (P < 0.05) at each collection period in gizzard contents but only at 43 d of age in the ileal digesta of broilers (P < 0.01). Log-quadratic increases (P < 0.05) of inositol concentrations were observed in gizzard and ileal digesta contents when increasing phytase activity from 0 to 40,500 FTU/kg at each collection period, which translated to a log-quadratic increase (P < 0.01) in plasma inositol concentration of broilers at 15, 29, and 43 d of age. Phytase supplementation up to 40,500 FTU/kg may benefit broilers by reducing phytate concentrations in the gizzard and ileal digesta contents. Moreover, inositol release in the ileal digesta may translate to increased plasma inositol concentration.

Tenacity of Enterococcus cecorum at different environmental conditions

AIMS

Our aim was to analyse the survival of Enterococcus cecorum (EC) at various temperatures, relative air humidities and on different substrates commonly existing in broiler houses.

METHODS AND RESULTS

A pathogenic EC isolate (EC14) was used to inoculate sterile litter, polyvinyl chloride (PVC) and dust samples. Incubation at 37, 25 or 15°C with either 32% relative humidity (RH) or 78% RH followed. At defined time points (0-4272 h post-inoculation), samples were examined in triplicate for the total viable count. Selected combinations were repeated for a non-pathogenic and two additional pathogenic EC strains. For EC14, the measured survival time ranged from 48 to 4272 h (178 days) depending on the substrate-humidity-temperature combination. The longevity was the highest on litter, followed by dust and then PVC. Lower temperatures facilitated its survival, lower relative air humidity favoured the survival only in combination with 25 or 15°C. All three pathogenic strains showed longer survival times (up to 432 h, 18 days) compared to the non-pathogenic EC strain (168 h, 7 days) under the same conditions.

CONCLUSIONS

Enterococcus cecorum demonstrates a high persistence in the environment especially at 15°C and 32% RH.

SIGNIFICANCE AND IMPACT OF THE STUDY

Hygiene management plans should consider the durability of EC and the risk of a carry-over to control consecutive EC outbreaks.

Effects of phytase-supplemented fermentation and household processing on the nutritional quality of Lathyrus sativus L. seeds

Grass pea (Lathyrus sativus L.) is commonly consumed in cooked, fermented, and roasted forms in Ethiopia. However, the impacts of household processing practices on its nutrients, antinutrients, and toxic compounds have not been adequately studied. Therefore, the effects of household processing and fermentation in the presence and absence of a phytase on the contents of β-N-oxalyl-L-α,β-diaminopropionic acid (β-ODAP), myo-inositol phosphates, crude protein, minerals and the in vitro bioaccessibility were investigated. Fermentation exhibited a significant decline in β-ODAP (13.0-62.0%) and phytate (7.3-90.5%) irrespective of the presence of phytase. Pressure and pan cooking after discarding the soaking water resulted in a 27.0 and 16.2% reduction in β-ODAP. A 30% reduction in phytate was observed during germination followed by roasting. In addition, germination resulted in a significant (p < 0.05) increase in crude protein. Germination and germination followed by roasting resulted in the highest Fe bioaccessibilities (more than 25 fold higher compared to untreated samples) followed by pressure cooking and soaking. Processing also improved Zn bioaccessibilities by 50.0% (soaked seed without soaking water), 22.5% (soaked seed with soaking water), and 4.3% (germination). Thus, the processing technologies applied were capable of reducing the content of phytate (InsP6) and β-ODAP with a concomitant increase in mineral bioaccessibilities. Processing of grass peas could therefore contribute to their more widespread utilization.

Fungal phytases: from genes to applications

Phytic acid stores 60-90% of the inorganic phosphorus in legumes, oil seeds, and cereals, making it inaccessible for metabolic processes in living systems. In addition, given its negative charge, phytic acid complexes with divalent cations, starch, and proteins. Inorganic phosphorous can be released from phytic acid upon the action of phytases. Phytases are phosphatases produced by animals, plants, and microorganisms, notably Aspergillus niger, and are employed as animal feed additive, in chemical industry and for ethanol production. Given the industrial relevance of phytases produced by filamentous fungi, this work discusses the functional characterization of fungal phytase-coding genes/proteins, highlighting the physicochemical parameters that govern the enzymatic activity, the development of phytase super-producing strains, and key features for industrial applications.

Effect of two commercial limestone sources with different solubility on the efficacy of two phytases in 0-21 d old broilers

A study evaluated the effects of limestone sources with different solubility on the efficacy of two phytases in broilers. A 2×5 factorial arrangement was employed with two commercial limestone sources and five diet treatments; a positive control (PC) diet with 7.2 g/kg P and 9.6 g/kg Ca, and a negative control diet containing reductions of 1.87 g/kg available P, 1.99 g/kg Ca and 0.4 g/kg Na, supplemented with either Buttiauxella phytase (PhyB) or Escherichia coli phytase (PhyE) at 500 or 1000 FTU/kg diet. The two limestone sources were feed-grade commercial products with different particle sizes and solubility (fast-soluble (FS) 100%; slow-soluble (SS) 26% soluble after 30 minutes at pH 3) containing similar levels of Ca. Diets were fed to one-day-old Ross 308 males (n=2,400) with 30 birds/pen and eight pens/treatment in two phases (starter 0-10 d and grower 10-21 d). On d 21, ileal digesta was collected from 12 birds/pen to determine apparent ileal digestibility (AID) of P and Ca, and myo-inositol hexakisphosphate (IP6) disappearance, and tibias from four birds/pen for ash determination. The SS limestone improved body weight gain (BWG), feed intake (FI) and FCR vs FS limestone in starter/grower phases (P<0.05), and improved AID of P (P<0.05) and IP6 disappearance (P<0.05) at d 21. There was an interaction between limestone and phytase on BWG, FI and FCR in the grower phase (P≤0.05) whereby FS (vs SS) limestone reduced BWG at either dose of PhyE, but only at 500 FTU/kg of PhyB. At an equivalent dose, PhyB had higher BWG and feed intake than PhyE (P<0.05). At 1000 FTU/kg, performance was equivalent (BWG and FI) or superior (FCR) to the PC, PhyB produced greater tibia ash, AID of P and IP6 disappearance (P<0.05). The findings showed that the effects of limestone particle size on phytase efficacy varied with phytase source and dose.

Buttiauxella phytase maintains growth performance in broilers fed diets with reduced nutrients under a commercial setting

The effect of down specifying nutrients in diets supplemented with Buttiauxella spp. phytase was studied in a commercial trial. Three treatments were tested with five replicate groups, each containing 700, one-day-old straight run Ross 308 broilers. Birds were fed pelleted diets from days 0-42 in four phases: starter (days 0-10); grower (days 11-21); finisher 1 (days 22-35) and finisher 2 (days 36-42). A nutritionally adequate, unsupplemented, positive control (PC) diet based on wheat, corn and soybean meal was compared against two down specified, negative control (NC) diets containing Buttiauxella phytase supplemented at 500 or 1000 FTU/kg. The reduction level was 0.134 and 0.159% unit for digestible phosphorus, 0.164 and 0.189% unit for calcium, 0.03 and 0.04% unit for sodium, 0.283 and 0.309 MJ/kg for nitrogen corrected apparent metabolizable energy in all phases and variable digestible amino acids in different phases, respectively for the diets containing the phytase at 500 and 1000 FTU/kg. An unsupplemented NC diet was not included, as it would have caused welfare and health issues. Weight gain and mortality-corrected feed conversion ratio for birds receiving phytase at either inclusion levels were equivalent to the PC group. Feed intake was increased by 500 FTU/kg phytase (P<0.05) during 0-21 d vs PC. Including 1000 FTU/kg phytase reduced water intake vs PC at 0-42 d and water-to-feed intake ratios, after the starter phase (P<0.05). Carcass yield in birds supplemented with either phytase level was not different from PC. Tibia ash was unaffected by treatment. Estimated feed costs (inclusive of phytase) were lower in supplemented than un-supplemented (PC) diets, by 10.0 to 13.7 €/ton diet. The trial demonstrated that reducing nutrient specifications of diets supplemented with Buttiauxella phytase maintained growth performance, lowered feed costs, with production benefits maximised at inclusion levels of 1000 FTU/kg.

Heterologous Expression of Histidine Acid Phytase From Pantoea sp. 3.5.1 in Methylotrophic Yeast Pichia Pastoris

Background and Objective:

The major storage form of phosphorus in plant-derived feed is presented by phytates and not digested by animals. Phytases are able to hydrolyze phytates and successfully used as feed additives. Nevertheless, nowadays, there is a constant search of new phytases and expression systems for better production of these enzymes. In this study, we describe cloning and expression of gene encoding histidine acid phytase fromPantoeasp. 3.5.1 using methylotrophic yeastPichia pastorisas the host.

Methods:

The phytase gene was placed under the control of the methanol-inducible AOX1 promoter and expressed inP. pastoris. Experiments of small-scale phytase expression and activity assays were used to test recombinant colonies. Four different signal peptides were screened for better secretion of phytase byP. pastoris. After 36 h of methanol induction in shake flasks, the maximum extracellular phytase activity (3.2 U/ml) was observed inP. pastorisstrain with integrated construct based on pPINK-HC vector andKluyveromyces maxianusinulinase gene signal sequence. This phytase was isolated and purified using affinity chromatography.

Results:

Recombinant phytase was a glycosylated protein, had a molecular weight of around 90 kDa and showed maximum activity at pH 4.0 and at 50°C. Recombinant phytase had excellent thermal stability – it retained high residual activity (100% ± 2%) after 1 hour of heat treatment at 70°C.

Conclusion:

The enhanced thermostability of the recombinant phytase, its expression provided by strong inducible promotor and the effectively designed expression cassette, the simple purification procedure of the secreted enzyme, and the possibility of large-scale expression make the foundation for further production of this bacterial phytase inP. pastorisat an industrial scale.

Research Note: Delay in sampling influences the profile of phytate in gizzard digesta and ileal digestibility of phosphorus in broilers

The objective of this study was to investigate the effect of different durations of time delay when sampling digesta from the gizzard and ileum of broilers on the degradation of myo-inositol hexakisphosphate (InsP₆) and digestibility of phosphorus (P). There was 1 experimental diet with a supplemental phytase activity of 1,212 phytase units/kg feed, which was provided to birds from day 13 to 18 after hatching. The diet was formulated to provide 6.6 g/kg Ca and 1.9 g/kg nonphytate P and fed to 24 cages of 6 birds. The 24 cages of birds were further randomly divided into 6 subgroups of 4 cages from which the digesta samples in the gizzard and ileum were collected at 0, 5, 10, or 20 min postmortem. The results showed that the concentration of InsP₆ decreased linearly (P = 0.002), InsP₅ decreased quadratically (P = 0.038), and the summation of concentrations of P in InsP_6-4 decreased linearly (P = 0.028) in the gizzard digesta with the increasing delay of sampling. In the ileum, the digestibility of phytate P tended to decrease linearly (P = 0.087), and the digestibility of total P decreased linearly (P = 0.026) with prolonged delay. In conclusion, delay in sampling could alter the measured profile of InsP esters in gizzard digesta probably because of a continued effect of supplemental phytase, while the ileal digestibility of total P could diminish. Therefore, standard sampling procedures should be implemented to minimize variance.

Effects of phytase supplementation on eggshell and bone quality, and phosphorus and calcium digestibility in laying hens from 25 to 37 wk of age

Effects of dietary available phosphorus (aP) and Ca levels and an Escherichia coli 6-phytase supplementation were studied in Lohmann LSL-Lite hens from 25 to 37 wk of age. Eighty-four hens were used in a completely randomized design with 7 treatments. The treatments were a positive control (PC) diet with 0.45% aP, 3.70% Ca, and 0.16% Na from 25 to 28 wk and 0.38% aP, 3.73% Ca, and 0.15% Na from 29 to 37 wk; a negative control (NC) diet, similar to the PC diet, with 0.22% aP, 3.00% Ca, and 0.13% Na from 25 to 28 wk and 0.19% aP, 3.02% Ca, and 0.13% Na from 29 to 37 wk; the NC diets supplemented with phytase at 150 (NC + 150), 300 (NC + 300), 600 (NC + 600), or 1,200 (NC + 1,200) phytase unit (FTU)/kg; and the PC diet supplemented with phytase at 1,200 (PC + 1,200) FTU/kg. Hen performance, eggshell, and bone quality were measured on a 4-wk basis. Bone breaking strength and ash and apparent ileal digestibility (AID) of P and Ca were determined at 37 wk. One- and 2-way ANOVA were conducted, and Tukey's range test was used to compare multiple means where P ≤ 0.05. No differences in hen performance, eggshell quality, bone breaking strength, bone ash, and P digestibility were observed between the PC and the NC treatments. The NC hens had lower cortical (P < 0.001) and trabecular + medullary bone mineral density (P = 0.004) and total bone mineral content (P < 0.001) than the PC hens. The PC + 1,200 increased cortical bone mineral density (P < 0.001). The reductions of aP and Ca in the NC diet were not deficient for performance but had a minor impact on bone mineralization. The NC + 600 and NC + 1,200 increased AID of P (P = 0.024), and all phytase treatments except the NC + 150 increased AID of Ca (P = 0.010) compared with the NC diet.

Bioprocess for Production, Characteristics, and Biotechnological Applications of Fungal Phytases

Phytases are a group of enzymes that hydrolyze the phospho-monoester bonds of phytates. Phytates are one of the major forms of phosphorus found in plant tissues. Fungi are mainly used for phytase production. The production of fungal phytases has been achieved under three different fermentation methods including solid-state, semi-solid-state, and submerged fermentation. Agricultural residues and other waste materials have been used as substrates for the evaluation of enzyme production in the fermentation process. Nutrients, physical conditions such as pH and temperature, and protease resistance are important factors for increasing phytase production. Fungal phytases are considered monomeric proteins and generally possess a molecular weight of between 14 and 353 kDa. Fungal phytases display a broad substrate specificity with optimal pH and temperature ranges between 1.3 and 8.0 and 37-67°C, respectively. The crystal structure of phytase has been studied in Aspergillus. Notably, thermostability engineering has been used to improve relevant enzyme properties. Furthermore, fungal phytases are widely used in food and animal feed additives to improve the efficiency of phosphorus intake and reduce the amount of phosphorus in the environment.

Phytate degradation in gnotobiotic broiler chickens and effects of dietary supplements of phosphorus, calcium, and phytase

Gnotobiotic broiler chickens were used to study interactive effects of supplemented phosphorus, calcium (PCa), and phytase (Phy) on myo-inositol 1,2,3,4,5,6-hexakis (dihydrogen phosphate) (InsP₆) degradation and release of myo-inositol in the digestive tract. In 2 subsequent runs, the chickens were subjected to 1 of 4 dietary treatments with and without PCa and Phy supplementation. Sanitized eggs were hatched in 8 germfree isolators, and a minimum of 9 male Ross 308 chickens were placed in each pen (total 16 pens). Treatments implemented on day 10 included gamma-irradiated diets without (PCa−; 4.1 g P and 6.2 g Ca/kg DM) or with (PCa+; 6.9 g P and 10.4 g Ca/kg DM) monosodium phosphate and limestone supplementation and without (Phy−) or with (Phy+) 1,500 FTU Phy/kg feed in a factorial arrangement. On day 15, digesta was collected from different sections of the intestinal tract and analyzed for InsP isomers and myo-inositol. The isolators did not remain germfree, but analysis of contaminants and results of InsP degradation indicated no or minor effects of the identified contaminants. Prececal InsP₆ disappearance was 42% with the PCa−Phy− treatment and 17% with PCa+Phy−. No InsP_3–4 isomers were found in the digesta of the terminal ileum in PCa−Phy−. The concentration of myo-inositol in the ileal digesta from PCa−Phy− (6.1 μmol/g DM) was significantly higher than that from PCa+Phy− (1.7 μmol/g DM), suggesting rapid degradation of the lower InsP isomers by mucosal phosphatases and their inhibition by PCa. Phytase supplementation increased InsP₆ disappearance and prevented inhibitory effects of PCa supplements (72% in PCa−Phy+ and 67% in PCa+Phy+). However, PCa supplementation reduced the degradation of lower InsP isomers mainly in the posterior intestinal sections in the presence of Phy, resulting in significantly lower myo-inositol concentrations. It is concluded that mucosa-derived phosphatases might significantly contribute to InsP₆ degradation in broiler chickens. The potential of mucosa-derived phosphatases to degrade InsP₆ and lower InsP is markedly reduced by dietary PCa supplementation.