Low digestibility of phytate phosphorus, their impacts on the environment, and phytase opportunity in the poultry industry

Review on Desirable Microbial Phytases as a Poultry Feed Additive: Their Sources, Production, Enzymatic Evaluation, Market Size, and Regulation

Poultry's digestive tract lacks hydrolytic phytase enzymes, which results in chelation of dietary minerals, vital amino acids, proteins, and carbohydrates, phytate-phosphate unavailability, and contamination of the environment due to phosphorus. Therefore, it is necessary to use exogenous microbial phytases as feed additive to chicken feed to catalyze the hydrolysis of dietary phytate. Potential sources of microbial isolates that produce desired phytases for chicken feed supplementation have been isolated from agricultural croplands. It is achievable to isolate phytase-producing bacteria isolates using both broth and agar phytase screening media. Potential substrates for submerged fermentation (SmF) for bacterial phytase production and solid-state fermentation (SSF) for fungal phytase production include rice and wheat bran. Following fermentation, saturated ammonium sulphate precipitation is typically used to partially purify microbial culture filtrate. The precipitate is then desalted. Measurements of the pH optimum and stability, temperature optimum and stability, metal ions stability, specificity and affinity to target substrate, proteolysis resistance, storage stability, and in vitro feed dephosphorylation are used to perform an enzymatic evaluation of phytase as an additive for poultry feed. The growth of the feed phytase market is primarily due to the expansion of chicken farms to meet the demand for meat and eggs from humans. The Food and Drug Administration in the USA and the European Food and Safety Authority are primarily in charge of putting rules pertaining to feed phytase use in chicken feed into effect. Conclusively, important components of the production of phytase additives for poultry feed include identifying a reliable source for potential microbe isolation, selecting an economical method of phytase production, thoroughly characterizing the biochemical properties of phytase, and comprehending the size and regulation of the current feed phytase market.

Effect of limestone particle size and microbial phytase on phosphorus and calcium digestion kinetics along the gastrointestinal tract in laying hens

1. This study assessed the effect of limestone particle size and microbial phytase incorporation on the fate of phosphorus (P) and calcium (Ca) along the gastrointestinal tract in 72 laying hens.2. Four experimental diets were formulated according to a 2 × 2 factorial arrangement to evaluate the effect of two coarse limestone (CL) inclusion. This included a mix (MIX) of 75% CL (2 - 4 mm) and 25% fine particles (FL, <0.5 mm) or 100% FL, in two different basal diets formulated without (MIX0 and FL0) or with 300 FTU of microbial phytase/kg (MIX300 and FL300).3. Contents of the crop, gizzard, duodenum, jejunum and ileum were collected to determine the mean retention time (MRT) of dry matter (DM), the recovery rate of Ca and P in each segment of the gastrointestinal tract and the apparent fractional digestibility coefficient (AD) of Ca and P in each intestinal segment.4. In hens fed FL, microbial phytase decreased the MRT of DM along the intestine (p < 0.05). In the crop and the gizzard, Ca recovery increased with MIX incorporation to a greater extent in hens fed without microbial phytase (p < 0.05). The mixed particle size incorporation decreased absorption kinetics of Ca in hens fed microbial phytase. The AD of P and the absorption kinetics of P were significantly decreased in hens receiving FL300, probably due to complex formation between Ca and phytic acid.5. This study showed that coarse limestone particles incorporation improved mineral utilisation along the digestive tract.

Nutritional and physiological responses to dietary phosphorus levels and phytase in pullets and laying hens

The objective of this study was to determine the effects of dietary available phosphorus (P) levels and dietary phytase added into the very low-P diet on the performance, mineral balance, odor emission, and stress responses in growing pullets and laying hens during 13 to 32 wk of age. One hundred sixty-eight pullets (Hy-Line Brown) were randomly assigned into 1 of 4 dietary treatments with 7 replicates of 6 birds each. Experimental diets were formulated to contain 3 graded P levels at 0.25, 0.35, and 0.45% during 13 to 15 wk (phase 1), 0.25, 0.35, and 0.45% during 16 to 18 wk (phase 2), and 0.20, 0.30, and 0.40% during 19 to 32 wk (phase 3). In addition, dietary phytase (500 FTU/kg matrix values) was added into the very low-P diets (0.20% during 13-15 wk, 0.25% during 16-18 wk, and 0.20% during 19-32 wk) to meet the nutritional adequacy with standard P diets. In all phases, decreasing dietary P levels did not affect (P > 0.05) growth, laying performance, and egg qualities. Decreasing dietary P levels linearly increased the relative duodenal and oviduct weights (P < 0.05), and quadratically increased the relative ovary weight in pullets (P = 0.016). Dietary phytase lowered (P = 0.021) the relative duodenal weight compared with the very low-P diet. Tibia breaking strength and tibia Mg contents in pullets were linearly lowered (P < 0.05) as dietary P levels decreased. Dietary phytase tended to increase (P = 0.091) tibia breaking strength and significantly increased (P = 0.025) tibia Mg content compared with the very low-P diet. Dietary P levels and dietary phytase affected (P < 0.05) ileal crypt depth and ileal villus height: crypt depth ratio in pullets. Decreasing dietary P levels linearly decreased (P < 0.01) crude fat digestibility and P excretion in both pullets and laying hens. Dietary phytase reversed (P < 0.05) the very low-P diet-mediated decrease of crude fat digestibility in pullets and laying hens. Dietary P levels and dietary phytase affected (P < 0.05) odor emission including ammonia in pullets and total volatile fatty acids in laying hens. Finally, lowering dietary P levels increased (P < 0.01) yolk corticosterone concentrations and the increased corticosterone concentration by the very low-P diet was reversed by dietary phytase. Collectively, our study shows that decreasing dietary P levels induced nutritional and physiological responses in pullets and laying hens and these P-mediated negative effects were mitigated by dietary phytase.

Effect of phytase supplementation on performance, fecal excretion, and compost characteristics in broilers fed diets deficient in phosphorus and calcium

This study investigated the effect of dietary supplementation with phytase on growth performance, fecal excretion, and compost nutrition on broilers fed available phosphorus (avP)- and calcium (Ca)-deficient diets. A total of 750 one-day-old broiler chicks were randomly divided into five dietary groups having ten replications in a floor house. Diets of the groups were formulated with positive control (PC), negative control (NC; low avP and Ca), and NC supplemented with phytase levels; 500 (NC500), 1,000 (NC1000), and 1,500 FTU/kg (NC1500). A three-phase feeding program was used in the trial. Average daily gain (ADG) and average daily feed intake (ADFI) in the groups fed diets supplemented with phytase were significantly (p < 0.05) higher than those fed NC and the increase was equivalent to those fed PC. Serum levels of Ca and phosphorus (P) were higher (p < 0.05) in broilers fed NC1000 and NC1500 than in those fed NC. Interleukin (IL) level was the lowest in the group fed NC. Plasma myo-inositol (INS) concentrations in the NC1500 group were higher (p < 0.05) than PC, NC, and NC500 groups. Crude protein (CP) excretion was notably (p < 0.05) lower in the NC1500 group than in PC and NC groups. A lower (p < 0.05) concentration of P2O5 was observed in compost from the group fed NC1500 than the groups fed PC and NC. Accordingly, we suggest that phytase supplementation in lower avP and Ca levels of broiler diet can improve their productive performance and reduce environmental pollution.

Elemental Profile in Chicken Egg Components and Associated Human Health Risk Assessment

Egg is a food product of high nutritional quality, extensively consumed worldwide. The objectives of this study were the determination of the elemental profile in eggs (egg white, yolk, and eggshell), the estimation of the non-carcinogenic health risk associated with the presence of heavy metals in investigated egg samples, and the development of statistical models to identify the best predictors for the differentiation of egg components. The assessments were carried out in a total set of 210 samples, comprising home-produced and commercial eggs, using inductively coupled plasma mass spectrometry. The results suggested measurable differences amongst hen eggs coming from different husbandry systems. The statistical models employed in this study identified several elemental markers that can be used for discriminating between market and local producer samples. The non-carcinogenic risk related to the consumption of the analyzed egg samples was generally in the safe range for the consumers, below the maximum permitted levels set by Romanian and European legislation. Food contamination is a public health problem worldwide, and the risk associated with exposure to trace metals from food products has aroused widespread concern in human health, so assessing the heavy metal content in food products is mandatory to evaluate the health risk.

The effects of dietary microbial 6-phytase on growth parameters, intestinal morphometric properties and selected intestinal genes expression in rainbow trout (Oncorhynchus mykiss, Walbaum 1876)

This study investigated the effects of dietary 6-phytase, produced by a genetically modified Komagataella phaffii, on growth performance, feed utilisation, flesh quality, villus morphometric properties, and intestinal mRNA expression in rainbow trout. Six iso-nitrogenous, iso-lipidic, and iso-caloric diets were formulated and fed to triplicate groups of juvenile rainbow trout weighing 32.57 ± 0.36 g (mean ± SD) for 90 days. The dietary treatments included two positive controls (PC), one formulated with 400 g/kg of fish meal named T1, and the other formulated with 170 g/kg of fish meal plus 1% avP derived from monocalcium phosphate named T2. The remaining dietary treatments consisted of a negative control (NC) formulated with 170 g/kg of fish meal (T3), NC+ 750, NC+ 1500, and NC+ 3000 OTU/kg levels of phytase designated as T4, T5, and T6 diets respectively. Compared to T1, weight gain (WG) increased by 16.29, 13.71 and 11.66% in T4, T5 and T6, respectively (p < 0.05). Feed conversion ratio (FCR) was lowered by 3.2 and 0.8% in T4 and T5 compared to T1 (p < 0.05). WG, feed intake (FI), FCR, final body length, bone ash, bone ash P, and intestinal morphometry were negatively affected in T3 fed fish (p < 0.05). Whole-body fish nutrient, bone ash, bone ash phosphorus (P) compositions and mucosal villus morphometric properties improved in rainbow trout fed diets supplemented with phytase dose ranging from 750-3000 OTU. Bone ash increased by 6.12% in T5 compared to T1 (p < 0.05). Phytase inclusion enhanced the profitability of feeding juvenile rainbow trout such diets as it reduced the feed price and economic conversion rate. Dietary inclusion of phytase down-regulated mRNA expression of genes responsible for fatty acid synthesis and lipogenesis in juvenile rainbow trout. Dietary phytase up-regulated the mRNA expression of genes (SLC4A11 and ATP1A3A) responsible for nutrient uptake and down-regulated intestinal expression of MUCIN 5AC-like genes (mucus secreting genes) in juvenile rainbow trout. Along with improving performance parameters, the inclusion of phytase in rainbow trout diet containing plant-based protein sources, can preserve intestinal morphology by regulating the mRNA expression of genes responsible for fatty acid synthesis, lipogenesis and nutrient uptake and transport.

Advances in immobilization of phytases and their application

The review describes the advances in the phytase immobilization for the past decade and their biotechnological applications. Different approaches for phytase immobilization are described including the process using organic and inorganic matrices and microbial cells, as well as nanostructures of various nature. Moreover, the immobilization of phytase-producing microbial cells and the use of cross-linked phytase aggregates have been under consideration. A detailed classification of various carriers for immobilization of phytases and the possibility of their applications are presented. A particular attention is drawn to a breakthrough approach of biotechnological significance to the design of microencapsulation of bacterial phytase from Obesumbacterium proteus in the recombinant extremophile of Yarrowia lipolytica.

Interaction among biofilter microbiome, fecal metabolome and water quality and regulation of sewage discharge in the recirculating aquaculture system of Apostichopus japonicus

With the aggravation of environmental pollution caused by traditional culture of Apostichopus japonicus, the concept of A. japonicus recirculating aquaculture system (RAS) came into being. To plan the sewage discharge time reasonably, we explored the temporal variation of water quality, biofilter microbe and fecal metabolome in RAS and relevant mechanism. The results showed that monitored water quality in RAS were within the safe living range of A. japonicus. Proteobacteria and Desulfobacterota were dominant bacteria in biofilter. The RDA results and correlation heatmap showed that NH₄-N and NO₂-N significantly affected the microbial community composition. The expression pattern of fecal metabolites changed with the passage of time after feeding. And ROC curve analysis and VIP bar chart showed that there were inter group biomarkers with predictive performance, which could help to remind timely sewage discharge. Topological analysis of KEGG pathway enrichment showed that metabolic pathways such as alanine, aspartate and glutamate metabolism changed significantly after feeding (P < 0.01). Additionally, the correlation analysis results showed that biofilter microbe and fecal metabolites were related to water quality (P < 0.05). Combined with the above research results, this study concluded that the RAS could discharge sewage 25-30 h after feeding. These findings were of direct significance to the management of RAS environment and the protection of A. japonicus healthy growth.

Effect of phytase and limestone particle size on mineral digestibility, performance, eggshell quality and bone mineralization in laying hens

The effect of microbial phytase and limestone particle size (LmPS) was assessed in Lohmann Tradition laying hens from 31 to 35 wk of age. Seventy-two hens were used in a completely randomized trial according to a 2 × 2 factorial arrangement with 2 levels of phytase/basal available P (aP); 0 FTU/kg with 0.30% aP or 300 FTU/kg with 0.15% aP, and 2 limestone particle sizes; fine particles (FL, <0.5 mm) or a mix (MIX) of 75% coarse limestone (CL, 2-4 mm) and 25% FL. Diets contained equivalent levels of Ca (3.5%), phytic P (PP; 0.18%), and aP (0.30%) considering the P equivalency of phytase. Thus, dietary treatments were FL0 and MIX0 without phytase, and FL300 and MIX300 with 300 FTU/kg phytase. Performance were recorded daily and eggshell quality (eggshell weight proportion, weight, thickness, and breaking strength) was measured weekly. At the end of the trial, bone parameters (tibia breaking strength, elasticity, and ash) and the apparent precaecal digestibility (APCD) of P and Ca were determined. No differences were observed between treatments in feed intake, FCR and bone parameters. Addition of MIX increased the eggshell proportion, weight and thickness in groups receiving no phytase (+6.5, +6.9, and +4.5%, respectively) while no effect was observed in groups receiving phytase (Phytase × LmPS, P < 0.05). In hens receiving FL, the APCD of P was lower in diets supplemented with phytase (-14 percentage points; Phytase × LmPS, P < 0.001). A higher phytate disappearance was observed in hens fed diets with phytase in combination with MIX (Phytase × LmPS, P = 0.005). Phytase and MIX together increased the APCD of Ca by 7.3 percentage points (Phytase × LmPS, P < 0.001). In conclusion, addition of CL could limit the formation of Ca-phytate complex thus improving the response of the birds to phytase compared to FL.

Broiler physiological response to low phosphorus diets at different stages of production

Phosphorus (P) inclusion in broiler diets needs to meet the physiological demands at a specific developmental stage to ensure the performance, health, and welfare of the birds and minimize nutrient losses. Toward a more efficient utilization of P in broiler husbandry, a timed nutritional conditioning strategy might enhance the endogenous mechanisms of mineral homeostasis and thus reduce dietary P supply of mineral sources. In this study, following a variable P supply in the starter phase, the effects of a dietary P depletion of broiler chickens were investigated at different developmental stages. Physiological adaptation mechanisms were elucidated based on zootechnical performance, endocrine parameters, regulation of intestinal P transport, bone characteristics, and health aspects. The results revealed a marked response to P depletion at the earliest developmental phase, after which indications of effective compensatory mechanism were detectable with advancing ages. Potential mechanisms that enable broilers to maintain mineral homeostasis primarily include endocrine control mediated by calcitriol actions, as well as intestinal P uptake and mineral mobilization from the bone. Conclusively, the precise timing, duration, and extent of a P depletion strategy in the broiler chicken might be considered for optimized nutrient utilization.

Effect of Phytase Level and Form on Broiler Performance, Tibia Characteristics, and Residual Fecal Phytate Phosphorus in Broilers from 1 to 21 Days of Age

The present study evaluated the individual and combined effects of coated and uncoated phytase on broiler performance, tibia characteristics, and residual phytate phosphorus (P) in manure. Two repeated studies were conducted using 240-day-old Cobb 500 by-product male broilers per trial. For each trial, birds were assigned to four treatments with four replicate battery cages per treatment (60 birds/trt) and grown for 21 days. Treatments included: (1) negative control (NC), (2) NC + 1000 phytase units (FTU) coated phytase (C), (3) NC + 1000 FTU uncoated phytase (U), and (4) NC + 500 FTU coated + 500 FTU uncoated phytase (CU). Data were analyzed with a one-way ANOVA and means were separated using Tukey’s HSD. In the pooled data for both trials, all treatments with dietary phytase had a higher body weight (BW) and feed consumption (FC) than the NC on day 21 (p < 0.05). Similarly, a six-point reduction was observed for day 1 to 21 feed conversion (FCR) for U and CU (p < 0.05). All treatments with phytase inclusion differed from the NC in every evaluated parameter for bone mineralization (p < 0.05) and had significantly lower fecal phytate P concentrations compared to the NC (p < 0.05). Overall, bird performance was essentially unaffected by phytase form, indicating that combining phytase forms does not appear to offer any advantage to the evaluated parameters from day 1 to 21.

The Growth Performance, Nutrient Digestibility, Gut Bacteria and Bone Strength of Broilers Offered Alternative, Sustainable Diets Varying in Nutrient Specification and Phytase Dose

This study assessed the use of locally sourced sustainable feed ingredients, rapeseed meal (RSM) and maize dried distiller grains with solubles (DDGS) in diets over traditional ingredients on the growth performance, bone strength and nutrient digestibility of broilers. This work also investigated the effects of supplementing exogenous phytase in two doses (500 vs. 1500 FTU/kg). Using male Ross 308 chicks (n = 320) assigned to receive one of four experimental diets: (1) Positive control diet 1 (PC1), a wheat, soya-based diet + 500 FTU/kg phytase. (2) Positive control diet 2, RSM/DDGS diet + 500 FTU/kg phytase (PC2). (3) Negative control (NC) reduced nutrient RSM/DDGS diet, no phytase. (4) The NC diet plus 1500 FTU/kg phytase (NC+). PC1 birds displayed higher feed intake and body weight gain consistently throughout the trial (p < 0.001) as well as increased body weight by 28 d and 42 d (p < 0.001). Whole-body dual emission X-ray absorptiometry (DXA) analysis revealed PC1 birds also had higher bone mineral density (BMD), bone mineral content (BMC), total bone mass, total lean mass and total fat mass than birds offered other treatments (p < 0.01). Diet had no significant effect on bone strength. Phytase superdosing improved the digestibility of dry matter (DM), neutral detergent fibre (NDF), gross energy (GE), calcium (Ca), potassium (K) and magnesium (Mg) compared to birds in other treatment groups. The phytase superdose also improved performance in comparison to birds offered the NC diet. Phytase superdosing increased the IP6 and IP5 degradation and increased the ileal inositol concentration of the birds. N excretion was lower for birds offered the traditional wheat−soya diet and highest for those offered the high-specification RSM/DDGS diet with a commercial dose of phytase. The addition of a phytase superdose to the negative control diet (NC+) reduced P excretion of birds by 15% compared to birds offered NC.

Combining analyses of metabolite profiles and phosphorus fractions to explore high phosphorus utilization efficiency in maize

Phosphorus (P) limitation is a significant factor restricting crop production in agricultural systems, and enhancing the internal P utilization efficiency (PUE) of crops plays an important role in ensuring sustainable P use in agriculture. To better understand how P is remobilized to affect crop growth, we first screened P-efficient (B73 and GEMS50) and P-inefficient (Liao5114) maize genotypes at the same shoot P content, and then analyzed P pools and performed non-targeted metabolomic analyses to explore changes in cellular P fractions and metabolites in maize genotypes with contrasting PUE. We show that lipid P and nucleic acid P concentrations were significantly lower in lower leaves of P-efficient genotypes, and these P pools were remobilized to a major extent in P-efficient genotypes. Broad metabolic alterations were evident in leaves of P-efficient maize genotypes, particularly affecting products of phospholipid turnover and phosphorylated compounds, and the shikimate biosynthesis pathway. Taken together, our results suggest that P-efficient genotypes have a high capacity to remobilize lipid P and nucleic acid P and promote the shikimate pathway towards efficient P utilization in maize.

The Effects of Inorganic Phosphorus Levels on Phosphorus Utilization, Local Bone-Derived Regulators, and BMP/MAPK Pathway in Primary Cultured Osteoblasts of Broiler Chicks

Understanding the underlying mechanisms that regulate the bone phosphorus (P) utilization would be helpful for developing feasible strategies to improve utilization efficiency of P in poultry. We aimed to investigate the effects of inorganic P levels on P utilization, local bone-derived regulators and bone morphogenetic protein/mitogen-activated protein kinase (BMP/MAPK) pathway in primary cultured osteoblasts of broiler chicks in order to address whether local bone-derived regulators or BMP/MAPK pathway was involved in regulating the bone P utilization of broilers using an in vitro model. The primary cultured tibial osteoblasts of broiler chicks were randomly divided into one of five treatments with six replicates for each treatment. Then, cells were respectively incubated with 0.0, 0.5, 1.0, 1.5, or 2.0 mmol/L of added P as NaH₂PO₄ for 24 days. The results showed that as added P levels increased, tibial osteoblastic P retention rate, number and area of mineralized nodules, the mRNA expressions of endopeptidases on the X chromosome (PHEX), dentin matrix protein 1 (DMP1), bone morphogenetic protein 2 (BMP2), and the mRNA and protein expressions of matrix extracellular phosphoglycoprotein (MEPE) increased linearly (p < 0.001) or quadratically (p < 0.04), while extracellular signal-regulated kinase 1 (ERK1) mRNA expression and c-Jun N-terminal kinase 1 (JNK1) phosphorylated level decreased linearly (p < 0.02) or quadratically (p < 0.01). Correlation analyses showed that tibial osteoblastic P retention rate was positively correlated (r = 0.452–0.564, p < 0.03) with MEPE and BMP2 mRNA expressions. Furthermore, both number and area of mineralized nodules were positively correlated (r = 0.414–0.612, p < 0.03) with PHEX, DMP1, MEPE, and BMP2 mRNA expressions but negatively correlated (r = −0.566 to −0.414, p < 0.04) with the ERK1 mRNA expression and JNK1 phosphorylated level. These results suggested that P utilization in primary cultured tibial osteoblasts of broiler chicks might be partly regulated by PHEX, DMP1, MEPE, BMP2, ERK1, and JNK1.

Mechanisms for improving phosphorus utilization efficiency in plants

BACKGROUND

Limitation of plant productivity by phosphorus (P) supply is widespread and will probably increase in the future. Relatively large amounts of P fertilizer are applied to sustain crop growth and development and to achieve high yields. However, with increasing P application, plant P efficiency generally declines, which results in greater losses of P to the environment with detrimental consequences for ecosystems.

SCOPE

A strategy for reducing P input and environmental losses while maintaining or increasing plant performance is the development of crops that take up P effectively from the soil (P acquisition efficiency) or promote productivity per unit of P taken up (P utilization efficiency). In this review, we describe current research on P metabolism and transport and its relevance for improving P utilization efficiency.

CONCLUSIONS

Enhanced P utilization efficiency can be achieved by optimal partitioning of cellular P and distributing P effectively between tissues, allowing maximum growth and biomass of harvestable plant parts. Knowledge of the mechanisms involved could help design and breed crops with greater P utilization efficiency.