Reduce Phosphorus Excretion Research Articles

Health effects of the New Nordic Renal Diet in patients with stage 3 and 4 chronic kidney disease, compared with habitual diet: a randomized trial

BackgroundChronic kidney disease (CKD) leads to an accumulation of waste products and causes adverse cardiometabolic effects. ObjectivesWe investigated the health effects of the New Nordic Renal Diet (NNRD), a novel meal pattern reduced in phosphorus, protein, and sodium. MethodsA 26-wk randomized trial compared the NNRD with a habitual diet. The NNRD group received weekly home deliveries of food and recipes. Monthly study visits included fasting blood samples, 24-h urine samples, blood pressure, and anthropometric measurements. Intention-to-treat analysis used linear mixed-effects models. ResultsSixty patients, mean estimated glomerular filtration rate (eGFR) 34 mL/min/1.73 m2 and body mass index of 25–27 kg/m2, were included and 58 completed. Metabolic syndrome was present in 53% (NNRD group) and 57% (control group). The NNRD group (n = 30) reduced their 24-h urine phosphorus excretion by 19% (−153 mg; 95% confidence interval [CI]: −210, −95), control group (n = 30) (no change), between-group difference −171 mg (95% CI: −233, −109; P < 0.001). Proteinuria was reduced by 39% in the NNRD group (−0.33 g/d; 95% CI: −0.47, −0.18), control group (no change), between-group difference −0.34 g/d (95% CI: −0.52, −0.17; P < 0.001). Plasma urea was reduced by −1.5 mmol/L in the NNRD group (95% CI: −2.1, −0.9), control group (no change), between-group difference −1.4 mmol/L (95% CI: −2.0, −0.7; P < 0.001). Systolic blood pressure fell by −5.2 mmHg in the NNRD group (95% CI: −8.4, −2.1), control group (no change), between-group difference −3.9 mmHg (95% CI; −7.6, −0.2; P = 0.04). The NNRD group lost −1.7 kg (95% CI: −2.6, −0.8), control group (no change), between-group difference −2.0 kg (95% CI: −3.0, −1.0; P < 0.001). There were no effects on eGFR during the 26-wk intervention. ConclusionNNRD in moderate CKD reduces phosphorus excretion, proteinuria, systolic blood pressure, and weight, mainly by reducing abdominal fat.This trial was registered at clinicaltrials.gov as NCT04579315.

Zinc, manganese, and copper amino acid complexes improve performance and bone characteristics of layer-type chicks under thermoneutral and cold stress conditions

Two experiments were designed to evaluate the effect of mineral-amino acid complexes (AACM) as a partial replacement of inorganic mineral (IM) in layer-type chicks' diets. Both studies had the same dietary treatments, where in experiment 1 (Exp. 1) was conducted under thermoneutral conditions from 0 to 35 D and chicks in experiment 2 (Exp. 2) were exposed to cold stress conditions at nighttime during the first 15 D and to thermoneutral condition from 16 to 35 D. For each trial, 1,200 one-day-old Lohmann Brown chicks were used, with 20 cage replicates with 30 chicks per cage. Treatments consisted of the control diet (IM; with 70, 70, and 8 mg/kg of zinc [Zn], manganese [Mn], and copper [Cu], respectively) and the treatment diet (AACM, with 40, 40, and 2.75 mg/kg of Zn, Mn, and Cu, respectively, from IM sources, along with 30, 30, and 5.25 mg/kg of Zn, Mn, and Cu, respectively). Data were submitted to analysis of variance, and means were compared using the t-test (P < 0.05). In Exp. 1, there were no significant differences between treatments on chick performance. However, AACM-fed chicks had higher thymus (P = 0.03) and cecum weight (P < 0.01), superior micromineral deposition in the tibias (P < 0.01), and reduced phosphorus excretion (P = 0.03). In Exp. 2, chicks fed with AACM had higher body weight gain (P = 0.04), better average daily feed intake (P = 0.03), lower phosphorus excretion (P = 0.02), and higher liver and pancreas weight (P < 0.01) in the last week of the study. In conclusion, chicks fed with AACM under thermoneutral conditions had higher bone mineralization and reduced excretion of phosphorus, and in adverse conditions, AACM improves performance and liver and pancreas weight, also reducing phosphorus excretion.

Reducing phosphorus excretion by horses

Abstract Phosphorus is both a limited, non-renewable resource and also a major factor in water eutrophication. Therefore, dietary P intakes should only provide what an animal requires, reducing unnecessary addition of P to diets and excretion into the environment. Equine feeding programs commonly include inorganic P in excess of requirements, because organic P (e.g. phytate-P) is thought to be poorly digested by the horse. We have observed that 95% of phytate is degraded by the time it reaches the feces, suggesting that phytate-P availability, and thus true P digestibility, may be greater than believed. In other species but not in horses, it is recognized that fecal P excretion is important for maintaining P homeostasis, but can result in low estimates of P digestibility and subsequently greater P requirements. Ideally, P digestibility values used to calculate requirements should only reflect dietary P availability and not fecal P excreted as part of maintaining homeostasis. This research evaluated two factors that could affect P excretion, a change in physiological state (from lactation to post-lactation) and weight loss. We found that post-lactational mares tended to excrete more P than control mares (P = 0.082), but fecal P excretion exceeded P intake for both groups of mares, and mares also lost weight during the study. In the following study, horses fed to lose weight tended to excrete more P than horses fed to gain weight (P = 0.085), suggesting fecal P excretion can be altered by physiological state independent of dietary P availability and is likely the main homeostatic mechanism for P. Previous studies that have not accounted for homeostatic P excretion may have underestimated P digestibility. Thus, requirements could be revised, resulting in a significant reduction in the amount of inorganic P added to equine diets and in the amount of P excreted into the environment. This research suggests that fecal P excretion can be altered due to physiological changes in the horse independent of actual dietary P digestibility and is likely the main homeostatic mechanism for P. Previous studies that have overfed P or failed to account for homeostatic fecal P excretion may have underestimated dietary P availability.

Reducing phosphorus excretion and loss potential by using a soluble supplement source for swine and poultry

Abstract Animal diets are often over-supplemented with low bioavailability phosphorus (P) sources in China, resulting in unnecessary excretion and loss of P to the environment. The effect of reducing dietary P supplementation and using a highly available P supplement for swine and poultry was determined. Manure collected in feeding trials involving the use of dicalcium phosphate (DCP) or mono-dicalcium phosphates (MDCP) that were

Effect of dietary phytase on phosphorus use efficiency and dynamics in aquaponics

Phytase is a phosphatase enzyme used as dietary supplement when significant portions of plant-based ingredients are used in fish feed formulations. This work thus assessed the effects of a phytase-supplemented diet on the P dynamics, P availability, P budget, fish and plant growth parameters, and carcass composition of Nile tilapia and phosphorus content of lettuce plants in aquaponic systems. The diet supplemented with phytase at the concentration of 1000 FTU kg−1 showed a significant increase in released phosphorus compared to the control in an in vitro assay. Phytase supplementation increased accumulation of phosphorus in fish carcass compared to the control, but did not affect growth performance. The addition of phytase to fish diets improved phosphorus utilization by fish, reducing phosphorus excretion. The lower amount of phosphorus excreted in the water caused by phytase did not impair the growth or phosphorus content of lettuce grown using the aquaponic nutrient solution. It is recommended that, even though the use of phytase in fish feeds increased the overall utilization of phosphorus in the present study, a small portion of inorganic phosphorus must be supplemented to meet minimum fish requirements.

Antibody to fibroblast growth factor 23-peptide reduces excreta phosphorus of laying hens

Novel strategies to minimize the excretion of phosphorus in swine and poultry are critical in minimizing environmental degradation. We have developed a synthetic peptide vaccine to produce autoantibodies to fibroblast growth factor 23 (FGF-23), a bone-derived hormone that blocks kidney phosphate resorption and indirectly reduces intestinal phosphate absorption. Single Comb White Leghorn laying hens, fed a standard diet (inorganic phosphorus, Pi = 0.4%), were immunized over the course of 4 weeks with either a FGF-23 peptide vaccine or adjuvant control (without FGF-23 peptide). At peak antibody titer to the peptide (week 5), 24-h excreta were collected and hens were blood sampled (represents 0.4% Pi treatment). Hens were then fed a 0.8% Pi diet and blood was sampled at 24 and 72 h and 24-h excreta were collected at 12 to 36 and 60 to 84 h (represents 0.8% Pi treatment). Increasing Pi from 0.4 to 0.8% increased (P < 0.05) percent excreta phosphorus, total 24-h phosphorus excretion, and plasma levels of FGF-23 and phosphate in either control or FGF-23 peptide vaccinated hens as early as the first sampling period. FGF-23 peptide vaccinated hens fed 0.4% Pi had reduced (P < 0.05) percent excreta phosphorus, total 24 h phosphorus excretion, and plasma levels of FGF-23 and iPTH, and increased (P < 0.05) plasma levels of phosphate and 1,25(OH)2 D3 when compared to control vaccinated hens fed 0.4% Pi. In the first collection period post 0.8% Pi feeding, FGF-23 peptide vaccinated hens had reduced (P < 0.05) plasma levels of FGF-23 and iPTH, and increased (P < 0.05) plasma levels of phosphate and 1,25(OH)2 D3, and tended to have reduced percent excreta phosphorus (P = 0.085) and total 24 h phosphorus excretion (P = 0.078) when compared to control vaccinated hens. Results during the second collection period post 0.8% Pi feeding were similar to that at the first collection period. These results are the first to show that the inhibition of FGF-23 action by a peptide vaccine (via neutralizing antibody) reduced phosphorus excretion. The approach presented provides new information on phosphorus metabolism in the laying hen.

ADIÇÃO DE ÁGUA EM RAÇÕES PARA SUÍNOS EM TERMINAÇÃO

To evaluate the effects of water addition to mash rations on nutrients and energy digestibility, water intake, excrement quality and carcass traits in pigs at the finishing phase, twelve commercial hybrid barrows with an initial weight of 64.0 ± 4.8 kg were used for the digestibility trial, and distributed into randomized blocks, based on the animals´ weight. Eighteen barrows and eighteen hybrid females, with an initial weight of 60.0 ± 3.6 kg, were used for the performance test, and distributed into a completely randomized design. Treatment one consisted of a dry diet formulated to meet the animals´ requirement. Treatments two and three consisted of the same diet with the addition of the same proportion of water and the double of water, respectively, the proportional unit used was kg. There was no statistical difference among treatments for the coefficients of apparent dry matter digestibility, gross energy, ether extract, calcium and phosphorus, and for the variables of performance, moisture, fecal nitrogen and phosphorus and carcass characteristics. There was a reduction of 27.97% of fresh water intake for animals receiving liquid diet. The addition of water to the diet of pigs at finishing phase does not influence apparent nutrient digestibility, or animal performance when they are fed twice a day. Moreover, it does not influence carcass composition, but decreases fresh water intake, lessening the waste when the animals go to the drinker, and it reduces phosphorus excretion, reflecting positively on the volume and polluting power of the excrements. KEYWORDS: Liquid feeding; performance; pig production; waste.

Effects of temperature, pH, incubation time and pepsin concentration on the in vitro stability of intrinsic phytase of wheat, barley and rye

Three experiments were conducted to evaluate the effects of temperature (T), pH, time of incubation and pepsin on the stability of intrinsic phytase of different cereals. Experiment one was conducted as a 3×4×3×3 factorial arrangement with three feed ingredients (rye, wheat and barley), four T (20, 38, 55 and 80°C), three pH levels (3.0, 5.5 and 8.0) and three incubation times (30, 60 and 120min), with two replicates per treatment. Stability was calculated as the ratio of the residual phytase activity of a treated sample to the non-treated (reference sample) times 100. Phytase activity of the reference samples of rye, wheat and barley was 3.14, 1.77 and 0.66FTU/g, respectively. Overall, rye showed the highest and barley the lowest stability (0.58 vs. 0.47, P<0.001). Stability decreased with increasing T to 0.07at 80°C across ingredients, pH levels and time of incubation (P<0.001). Stability of intrinsic phytase decreased with increasing incubation time (P<0.001). Stability was highest at pH 3.0 and lowest at pH 8.0, respectively (0.65 vs. 0.34 across ingredients, T and time of incubation, P<0.001). Combinations of low pH and low temperatures (20 and 38°C) resulted in the highest stability of intrinsic phytase (>0.90). Wheat and rye phytases were stable at pH 3.0 and 5.5 (20 and 38°C). In experiment two, the effect of shorter period of time (10 and 30min) was assessed on the stability of cereal phytases. Barley phytase showed the highest residual phytase activity among cereals at 65°C. In experiment three, stability of intrinsic phytase of these feed ingredients was determined after incubation in different concentrations of pepsin (0, 5 and 10mg/mL) at pH 2.0. Intrinsic phytases of wheat and rye were resistant to pepsin, but barley phytase was susceptible to pepsin and its stability decreased to 0.57 after pre-incubation for 60min in 5mg pepsin/mL. This knowledge regarding the effect of T, incubation time and pH on stability of cereal intrinsic phytases may contribute to optimize available P contents of diets, thereby reducing phosphorus excretion of monogastrics.

Quantifying phytate in dairy digesta and feces: Alkaline extraction and high-performance ion chromatography

Development of an analytical method with appropriate combination of extraction and quantification approaches for undigested phytate in ruminant feces and digesta will advance knowledge of phytate degradation in ruminants and help to reduce phosphorus excretion. Established quantification methods give satisfactory results for feedstuffs and nonruminant manure but recovery of phytate is incomplete for ruminant feces and digesta because of their complex sample matrix and low ratio of phytate to inorganic P. The objective was to develop a robust, accurate, sensitive, and inexpensive method to extract and quantify phytate in feeds, ruminant feces, and digesta. Diets varying in phytate content were fed to dairy heifers, dry cows, and lactating cows to generate digesta and fecal samples of varying composition to challenge extraction and quantification methods. Samples were extracted with 0.5 M HCl or 0.25 M NaOH + 0.05 M EDTA. Acid extracts were mixed with 20% NaCl, alkaline extracts were acidified to final pH <2, and then both extracts were clarified with C18 cartridges and 0.2-μm filters. High-performance ion chromatography (HPIC) was used to quantify phytate. In feed samples, the measured phytate was comparable in alkaline and acid extracts (2,965 vs. 3,085μg/g of DM). In digesta and fecal samples, alkaline extraction yielded greater estimates of phytate content than did acid extraction (40.7 vs. 33.6 and 202.9 vs. 144.4μg/g of DM for digesta and fecal samples, respectively). Analysis of alkaline extracts by HPIC is usually not possible because of sample matrix interferences; acidification and C18-cartridge elution of alkaline extracts prevented this interference. Pure phytate added to dry samples before extraction was almost completely recovered (88 to 105%), indicating high extraction efficiency, no adverse effect of extract clean-up procedures, and accurate quantification of phytate. The proposed method is rapid, inexpensive, robust, and combines the extraction power of NaOH-EDTA with the precision and sensitivity of HPIC quantification, allowing accurate quantification of phytate in feeds, ruminant digesta, and fecal samples.

The phytase from antarctic bacterial isolate, Pseudomonas sp. JPK1 as a potential tool for animal agriculture to reduce manure phosphorus excretion

Intracellular phytase activity was found in the Antarctic bacterial isolate, JPK1. Based on 16S rRNA gene sequence analysis, the strain was related to Pseudomonas sp. The optimal activity of JPK1 phytase occurred at 50°C and pH 5.0 to 5.5. The enzyme was highly specific for phytate with little or no other phosphate conjugates. Enzyme activity was strongly inhibited by Cu2+ and Zn2+, and completely inactivated by sodium dodecyl sulfate. The enzyme effectively liberated inorganic phosphate from wheat bran, a main feedstuff with high phytate content. The enzyme may be a good candidate for use as an environmental-friendly feed additive to enhance the nutritive value of phytate and reduce phosphorus pollution. Key words: Antarctic, phytase, Pseudomonas sp., phytate, feed additive.

Registration of LP1–2581, LP1–2163H, LP3–1159, and LP640–1304 Low‐Phytate Spring Barley Germplasm Lines

The Agricultural Research Service, U.S. Dep. of Agriculture (USDA‐ARS) has developed and released four low‐phytate spring barley (Hordeum vulgare L.) germplasm lines: LP1–2581 (Reg. No. GP‐196, PI 658245), LP1–2163H (Reg. No. GP‐199, PI 658248), LP3–1159 (Reg. No. GP‐198, PI 658247), and LP640–1304 (Reg. No. GP‐197, PI 658246). The low phytate trait derives from sodium azide‐induced mutations. In these lines, phytate—the primary form of phosphorus in grain—is significantly reduced, and inorganic phosphorus is increased. Total phosphorus is unchanged or reduced slightly. Phytate cannot be digested by monogastric animals and is an effective chelator of nutritionally important minerals. Low‐phytate barley has been associated with increased phosphorus and mineral nutrition and reduced phosphorus excretion when fed to monogastric animals. Each of these lines represents a unique combination of genetic background and a low‐phytate allele. Each mutant allele represents a mutation at a different locus. These lines may be useful for the production of future low‐phytate cultivars or for genetic and biochemical studies.

Suplementação dietética de fitase sobre o metabolismo de nutrientes de frangos de corte

O experimento foi conduzido com os objetivos de avaliar o efeito da suplementação de fitase em dietas sobre a energia metabolizável (EMAn) e sobre os coeficientes de digestibilidade ileal aparente de matéria seca, proteína bruta, cálcio e fósforo e determinar a deposição de cinzas, cálcio e fósforo na tíbia de frangos de corte. Foram utilizados 350 frangos de corte machos Ross de 16 a 25 dias de idade, distribuídos num delineamento inteiramente ao acaso, com cinco dietas e dez repetições de sete aves por unidade experimental. As dietas, à base de milho e de farelo de soja, foram formuladas considerando a disponibilidade de energia metabolizável, proteína bruta, lisina, cálcio e fósforo disponível, de acordo com a matriz nutricional da enzima fitase, e suplementadas com 0,5% de oxido crômico. As dietas foram: controle positivo; controle negativo 1; controle negativo 2; controle negativo 1 + 250 uft; controle negativo 2 + 500 uft. A suplementação de enzima fitase nos níveis de 250 e de 500 uft/kg de dieta melhorou os valores energéticos das dietas, que aumentaram, em média, 36 e 54 kcal/kg de MS, respectivamente. A utilização de fitase melhorou os coeficientes de digestibilidade da proteína bruta e do fósforo, cujos maiores valores foram obtidos com a suplementação de 500 uft/kg de ração. A suplementação de fitase melhorou o coeficiente de digestibilidade e a retenção de fósforo, reduzindo o fósforo excretado, e aumentando a composição de fósforo na tíbia das aves, principalmente nos frangos de corte alimentados com a dieta suplementada com fitase (500 uft/kg). A suplementação de fitase (500 uft/kg) melhora o coeficiente de digestibilidade da proteína bruta e do fósforo, melhora a retenção de fósforo e diminui a excreção de fósforo de frangos de corte.

Comparison of Selected Physicochemical Characteristics of Commercial Phytases Relevant to their Application in Phosphate Pollution Abatement

The enzyme phytase catalyses the dephosphorylation of phytic acid and it's salts, phytates. Supplementation of monogastric animal feed with microbial-derived phytase increases the bioavailability of phytic acid bound phosphate. This facilitates a reduction in the addition of inorganic phosphate to the feed and reduces phosphorus excretion. To achieve maximum efficacy in terms of phosphate pollution abatement, supplemental phytases added to animal feed must survive thermal processing of the feed, resist inactivation by the proteolytic enzymes encountered in the animal's digestive tract and display high activity at physiological temperature and pH. A series of in vitro experiments were carried out to determine the relative suitability of four major commercial phytase products for use in animal feed. The enzymes assessed lost between 14% and 72% of their original activities after heating to 80°C for 5 minutes. After exposure to simulated upper digestive tract conditions, the phytases assessed retained between 0 and 28% of their original activities. The commercial phytases displayed between 98% and 67% of their maximum activities at 39°C and all phytases assessed had an optimum pH between pH 4 and pH 5. None of the phytases assessed satisfied all of the criteria of an ideal phytase for use in animal feed.

Efficiency of phosphorus utilization in dairy operations (2006)

Efficient utilization of nutrients is a must on modern dairies. Most of the phosphorus arriving at the dairy will either be found in purchased feedstuffs or commercial fertilizer used to raise grain and forage for the dairy. In general, those dairies that purchase all feeds are more efficient with phosphorus utilization than those that grow forage and grain. This is likely due to increased inefficiencies associ-ated with feeding and crop enterprises. Care-ful evaluation of diets to reduce feeding ex-cess phosphorus can reduce phosphorus excre-tion in the manure by as much as 50%. This not only reduces input costs, but also reduces the total cost of land application. The most efficient way to manage dairy farm nutrients is to develop a comprehensive nutrient manage-ment plan that includes both the cropping and animal enterprises. This plan will help pro-ducers predict phosphorus requirements of cattle and crops, and then allow the producer to control phosphorus inputs to meet the re-quirements.; Dairy Day, 2006, Kansas State University, Manhattan, KS, 2006

Dietary Strategies for Reduced Phosphorus Excretion and Improved Water Quality

Cost effective feeding strategies are essential to deal with P surpluses associated with intensive animal agriculture and the consequent impact on water quality. Reduction of P overfeeding, use of feed additives to enhance dietary P utilization, and development of high available phosphorus (HAP) grains have all been shown to decrease fecal P excretion without impairing animal performance. Much progress has been made, but more research will be needed to refine these strategies to maximize reductions in P excretion while maintaining animal performance. Recent research has focused on the impact of modifying dietary P on the forms of P excreted and the mobility of P in soils amended with these manures, with strong treatment trends becoming evident in the literature. In general, dietary strategies have been developed that can effectively reduce the total P concentration in manures produced, and combining strategies usually leads to greater reductions than individual practices. However, the impact of different approaches on the solubility of P in manures and amended soils has been more variable. Soluble P remains of particular concern due to links between solubility of P in manure and P losses from manure-amended soils. In this paper, we outline the major strategies for reducing dietary P in different species, review the literature on the impact of these approaches on P forms in manures and amended soils, and discuss the potential beneficial effects on animal agriculture and the environment.

Biotechnological production and applications of phytases

Phytases decompose phytate, which is the primary storage form of phosphate in plants. More than 10 years ago, the first commercial phytase product became available on the market. It offered to help farmers reduce phosphorus excretion of monogastric animals by replacing inorganic phosphates by microbial phytase in the animal diet. Phytase application can reduce phosphorus excretion by up to 50%, a feat that would contribute significantly toward environmental protection. Furthermore, phytase supplementation leads to improved availability of minerals and trace elements. In addition to its major application in animal nutrition, phytase is also used for processing of human food. Research in this field focuses on better mineral absorption and technical improvement of food processing. All commercial phytase preparations contain microbial enzymes produced by fermentation. A wide variety of phytases were discovered and characterized in the last 10 years. Initial steps to produce phytase in transgenic plants were also undertaken. A crucial role for its commercial success relates to the formulation of the enzyme solution delivered from fermentation. For liquid enzyme products, a long shelf life is achieved by the addition of stabilizing agents. More comfortable for many customers is the use of dry enzyme preparations. Different formulation technologies are used to produce enzyme powders that retain enzyme activity, are stable in application, resistant against high temperatures, dust-free, and easy to handle.

Altering Dietary Cation-Anion Difference in Lactating Dairy Cows to Reduce Phosphorus Excretion to the Environment

Four early-lactating dairy cows were randomly allocated to 4 diets with dietary cation-anion difference [DCAD; (Na + K)−(Cl− + S2−) mEq/100g dry matter)] values of +14, +18, +24, and +45. Diets were formulated to be isoenergetic and isonitrogenous, and supplied similar levels of P (0.46%) and Ca (0.77%). The salts, MgCl2, MgSO4, K2CO3, and NaHCO3 were used to alter DCAD. The main objective of the study was to ascertain whether a decrease in DCAD would reduce fecal P excretion in lactating dairy cattle. The experiment was conducted as a 4×4 Latin square design with 21-d periods. During the last 5 d, diets were offered at a restricted level and samples of blood, milk, feces, and urine were collected. Measures of acid-base status of the cows were linearly related to DCAD, but the animals did not experience metabolic acid stress. Neither fecal P nor urinary P was affected by DCAD, and there was no change in overall P balance. Plasma P tended to increase and blood concentrations of ionized Ca were enhanced as DCAD decreased; P excretion in milk showed a quadratic response to DCAD. Milk yield and milk composition were unaffected by changes in DCAD. Although DCAD may have influenced P homeostasis in lactating cows, there was no evidence that, within the range of + 14 to + 45 mEq/100g dry matter, DCAD could be used as a nutritional strategy to reduce manure P from dairy cattle.

Additives to reduce phosphorus excretion and phosphorus solubility in poultry and swine manure

In the past 20 years, scientists have realised that environmental contamination by non-point source nutrients is a significant problem and its control is not easily managed. Manure phosphorus was found to be a primary pollutant of surface water, so methods to reduce manure phosphorus runoff have been a research focus. This review concentrates on approaches developed to reduce the excretion of manure phosphorus and to reduce the soluble phosphorus content of manure by poultry and swine. Addition of phytase to poultry and swine diets reduces phosphorus excretion dramatically. For example, phytase addition lowered broiler manure phosphorus by 10–56%, hen manure phosphorus by 41%, growing–finishing pig manure phosphorus by 21–51% and weaning–growing pig manure phosphorus by 20–25%. Phytase also improves the availability of other nutrients. Addition of vitamin D and its metabolites increases phosphorus retention by 31–79%, while use of this vitamin and its metabolites with phytase improved phosphorus retention by 79%. Further research is needed in the use of organic acids, probiotics and starch and their impact on manure phosphorus reduction. Ratios of dietary calcium:total phosphorus in the range of 1.1:1 to 1.4:1 appear to provide the best efficiency of supplemental phytase and D3 in broilers. Determination of dietary phosphorus requirements for each growth phase is vital, as is accurate and quick measurement of phosphorus contents in feeds. Certain chemical reagents containing aluminium, calcium or iron have been found effective in reducing the solubility of phosphorus, when added to manure or litter. Research reports have shown that reagents containing aluminium reduced phosphorus solubility in manure by 39–100%. Compounds containing iron decreased phosphorus solubility by 48–95%, while calcium compounds reduced soluble phosphorus by 65%. Fly ash containing aluminium, iron and calcium may also be used to lower soluble phosphorus content in manures.

Comparison of Normal and High Available Phosphorus Corn With and Without Phytase Supplementation in Diets for Male Large White Turkeys Grown to Market Weights

Large White turkeys were fed diets containing either normal yellow dent corn (YDC) or a corn mutation containing low phytate phosphorus and high available phosphate corn (HAPC). Diets were considered nutritionally adequate in all respects with various degrees of reduction in available phosphorus content ( - 0.0, - 0.05, - 0.10 or - 0.15% of NRC (1994) recommendations for different feeding periods). These diets were fed with or without the addition of 1000 U/kg of phytase enzyme (Natuphos , BASF), resulting in ® a total of 16 dietary treatments. Each treatment was assigned to three pens of 20 male turkeys from day-old to 20 wk of age. Body weight, feed consumption, and tibia ash were determined at 28 d intervals during the study. Male turkeys fed diets with HAPC did not differ significantly in BW or feed conversion (FC) from those fed diets with YDC, and had significantly higher tibia ash at 4, 8, and 12 wk of age. Addition of 1000 U/kg of phytase resulted in significantly higher BW at 4, 8, 12, and 16 wk of age as compared to unsupplemented controls with no significant differences in FC. The addition of phytase significantly improved tibia ash at every age. Dietary phosphorus content had no effect on BW or FC at any age. Reduction of phosphorus generally did not impair tibia ash until reduction of 0.15% below NRC (1994) recommendations. Addition of phytase aided in overcoming the reduction in phosphorus content. The combination of HAPC, addition of phytase, and reduction in dietary phosphorus content should aid in reducing phosphorus excretion without impairing performance.

Total and phytate-phosphorus contents and phytase activity ofAustralian-sourced feed ingredients for pigs and poultry

A total of 160 samples of 20 Australian-sourced feed ingredients of plant origin for pigs and poultry was analysed for total phosphorus and phytate-phosphorus contents and endogenous phytase activity. The majority of total P was present as phytate-phosphorus, and these concentrations were significantly correlated in 9 feed ingredients. The endogenous phytase activity in tested feed ingredients was negligible other than for wheat, its by-products and barley. Phytate-phosphorus was determined by a standard 'ferric chloride precipitation' method, which was satisfactory for individual feed ingredients, with the exception of lupins and faba beans. It appears that phytate is more difficult to extract from these two feedstuffs, possibly because of the affinity of phytate for protein. Ferric chloride precipitation methods are not suitable for phytate-phosphorus determinations of complete feed samples containing other sources of phosphorus, which is a distinct limitation. A lesser limitation is that these methods cannot distinguish between the various esters of myo-inositol phosphate present. Given the variation of phytate contents within ingredients, particularly wheat, the desirability of determining dietary substrate levels is emphasised to take full advantage of including exogenous phytases in pig and poultry diets to reduce phosphorus excretion and abate phosphorus pollution.