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PubMed1993

Dietary 1,25-dihydroxycholecalciferol supplementation increases natural phytate phosphorus utilization in chickens.

These studies were conducted to determine if supplementation of a corn-soybean meal diet with 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] would increase the utilization of natural phytate phosphorus by broiler chickens. Two experiments were conducted to evaluate the effect of dietary 1,25-(OH)2D3 in the presence and absence of supplemental phytase and at several dietary levels of inorganic phosphorus supplementation. The criteria measured in these studies were weight gain, gain:feed ratio, bone ash, rickets due to phosphorus deficiency, plasma calcium and phosphorus and retention of calcium, phosphorus and phytate phosphorus. In the first experiment, the types and amounts of fecal inositol phosphates were determined by HPLC, and the total fecal phytate was determined by the classic FeCl3 precipitation technique. In the first experiment, the addition of 1,25-(OH)2D3 to the diet in the presence of dietary phytase resulted in greater 9-d weight and bone ash and lower incidence of rickets; the retention of total fecal phytate and phytate phosphorus was greater than in controls. The second experiment was a complete 2 x 2 x 2 factorial design [phosphorus levels x phytase x 1,25-(OH)2D3]. The addition of 1,25-(OH)2D3 alone to the diet resulted in greater 9-d weight and bone ash, lower incidence of rickets, and greater retention of total calcium and phosphorus and phytate phosphorus. The highest retention of phytate phosphorus (79.4%) was obtained when both phytase and 1,25-(OH)2D3 were present in the diet. The possible mode of action and importance of these results in many areas of nutrition and environmental science are discussed.

6-Phytase↗
PubMed1997

Effect of diets varying in nitrogen or phosphorus content on indicators of bone growth in lambs.

Growing lambs were fed diets low in nitrogen and phosphorus (LNLP), low in nitrogen and high in phosphorus (LNHP), high in nitrogen and low in phosphorus (HNLP) or high in nitrogen and phosphorus (HNHP) and the effects on bone growth and on blood and urinary bone marker levels or excretion rates were monitored. Plasma calcium concentrations were higher, and phosphorus concentrations lower, in lambs fed the low phosphorus diets but there were no differences in plasma 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) concentrations. Lambs fed both low phosphorus diets (LNLP and HNLP) had lower plasma osteocalcin and higher bone-specific alkaline phosphatase concentrations than those fed the high phosphorus diets. Urinary pyridinoline and deoxypyridinoline excretion were also affected by treatment, with their rates of excretion being highest in lambs fed the diet low in both nitrogen and phosphorus (LNLP). Lambs fed the low phosphorus diets were lighter in weight at slaughter and had lighter bones that were less well mineralized than those fed the high phosphorus diets. Reducing the nitrogen content of the diet appeared to have little effect on bone composition. These results suggest that bone markers that have proved useful in the diagnosis and treatment of bone disease are sensitive to variation in nutrient supply and may prove useful in early detection of nutrient deficiencies that affect bone growth.

Animals↗
PubMed1987

Quantitation of phosphorus excretion in sheep by compartmental analysis.

The control of phosphorus excretion in sheep has been examined by constructing a kinetic model that contains a mechanistic set of connections between blood and gastrointestinal tract. The model was developed using experimental data from chaff-fed sheep and gives an accurate description of the absorption and excretion of phosphorus in feces and urine of the ruminating sheep. Simulation of the response to an intravenous phosphorus infusion by adding an inflow of 2 g/day of phosphorus into the compartment describing blood, predicted values for fecal output of phosphorus lower than found experimentally. However, by alteration of the parameters describing absorption or salivation, the predictions approached experimental values. Similarly simulation of the conditions existing when a liquid diet was infused directly into the abomasum, i.e., a decrease in salivation rate [L(4.1)] and dietary phosphorus entering compartment 5 (abomasum) instead of compartment 4 (rumen), gave incorrect predictions for plasma and urinary phosphorus, but when the parameter for urinary phosphorus was increased the predicted values approached experimental values. These results indicated the main control site for phosphorus excretion in the ruminating sheep was the gastrointestinal tract, whereas for the nonruminating sheep fed the liquid diet, control was exerted by the kidney. A critical factor in the induction of adaptation of phosphorus reabsorption by the kidney was the reduction in salivation, and since this response occurred independently of marked changes in the delivery of phosphorus to the kidney, a humoral factor may be involved in this communication between salivary gland and kidney.

Animals↗
PubMed1976

Reversible changes of the muscle cell in experimental phosphorus deficiency.

Both animal and human studies suggest that either phosphorus depletion or hypophosphatemia might have an adverse effect on muscle function and composition. Recently a possible deleterious effect was noted in patients with chronic alcoholism. In this unexplained disease, a variety of toxic and nutritional disturbances could affect the muscle cell, thus obscuring the precise role of phosphorus. Accordingly, we examined eight conditioned dogs for the possibility that phosphorus deficiency per se might induce an abnormally low resting transmembrane electrical potential difference (Em) and alter the composition of the muscle cell. Eight conditioned dogs were fed a synthetic phosphorus-deficient but otherwise nutritionally adequate diet plus aluminum carbonate gel for a 28-day period followed by the same diet with phosphorus supplementation for an additional 28 days. Sequential measurements of Em and muscle composition were made at 0 and 28 days during depletion and again after phosphorus repletion. Serum inorganic phosphorus concentration (mg/100 ml) fell from 4.2 +/- 0.6 on day 0 t0 1.7 +/- 0.1 on day 28. Total muscle phosphorus content (mmol/100 g fat-free dry wt [FFDW]) fell from 28.5 +/- 1.8 on day 0 to 22.4 +/- 2.1 on day 28. During phosphorus depletion, average Em (-mV) fell from 92.6 +/- 4.2 to 77.9 +/- 4.1 mV (P less than 0.001). Muscle Na+ and Cl- content (meq/100 g FFDW) rose respectively from 11.8 +/- 3.2 to 17.2 +/- 2.8 (P less than 0.01) and from 8.4 +/- 1.4 to 12.7 +/- 2.0 (P less than 0.001). Total muscle water content rose from 331 +/- 12 to 353 +/- 20 g/100 FFDW (P less than 0.05). A slight, but nevertheless, significant drop in muscle potassium content, 43.7 +/- 2.0-39.7 +/- 2.2 meq/100 g FFDW (P less than 0.05) was also noted. After 4 wk of phosphorus repletion, all of these measurements returned toward control values. We conclude that moderate phosphorus depletion can induce reversible changes in skeletal muscle composition and transmembrane potential in the dog, and it apparently occurs independently of profound hypophosphatemia.

Animals↗
PubMed1992

Effect of inorganic phosphate source and dietary phosphorus level on laying hen performance and eggshell quality.

Two experiments were conducted to evaluate laying hen performance when fed two sources of inorganic phosphorus. In Experiment 1, a regular and a coarse form of defluorinated phosphate and one source of dicalcium phosphate were used in diets calculated to contain either .4 or .5% total phosphorus (.2 or .3% nonphytate phosphorus). In Experiment 2, either the regular form of defluorinated phosphate or the dicalcium phosphate source was fed in diets calculated to contain either .4, .5, .6, or .7% total phosphorus (.2, .3, .4, or .5% nonphytate phosphorus). In Experiment 1, hens fed .5% total dietary phosphorus consumed more feed and produced heavier eggs (P less than or equal to .05). Hens fed the .4% dietary phosphorus level lost more weight during the experiment (P less than or equal to .05). No differences among dietary treatments existed for egg specific gravity. A significant source by level interaction occurred for the farm classification of thin-shelled, cracked, or broken eggs and for the total of these classifications. In Experiment 2, egg production, feed consumption, egg weight, and egg mass were depressed (P less than or equal to .05) at the .4% total dietary phosphorus level. Hens fed the .4 and .7% total dietary phosphorus level laid eggs with the highest and lowest egg specific gravity, respectively. This trend was inverse to the effect of these phosphorus levels on egg weights. A significant source by level interaction occurred for the farm classification of thin shell and for the total percentage of eggs with exterior defects. At the .4% total phosphorus level, the regular form of defluorinated phosphate produced eggs with a significantly greater thin shell classification than the dicalcium phosphate source. Hens fed the dicalcium phosphate source produced a higher percentage of compressed-sided and misshapen eggs.

Animals↗
PubMed2001

[Release character of phosphorus from the sediments of east Lake, Wuhan].

Effects of environmental factors on the release of phosphorus were studied at laboratory simulated test. The relationship between the different forms of phosphorus in sediments and the quantity of releasing phosphorus was studied at the same time. Results showed that the rates of phosphorus release from the sediment increased with rising the temperature of disturbing the overlying water. The content of phosphorus release from the sediment reached the lowest level when pH value was 7.4, high pH or low pH increased the rates of phosphorus release from the sediment. In anaerobic, the release rates of phosphorus was 30 times as much as in aerobic. Research also showed that different chemical forms of phosphorus in sediments were related to the quantity of phosphorus released from the sediments in varying degrees. The dissolved phosphorus and Fe binding phosphorus in sediments played the most important roles (r > 0.90, P < 0.01).

China↗
PubMed2001

Parathyroid hormone changes during phosphorus load in patients with chronic renal insufficiency with low serum parathyroid hormone or adynamic bone disease.

UNLABELLED: Adynamic bone disease (ABD) is frequently associated with low serum parathyroid hormone (PTH) concentrations. Many clinical and therapeutic conditions have been associated with ABD, and recently, a low phosphorus intake accompanied by low serum concentration of phosphorus and PTH has been described. AIM: To evaluate the parathyroid gland response of chronic renal insufficiency patients (CRI) with low serum PTH or ABD to a phosphorus load. METHODS: We examined the effects of 0.5 and 1.0 g/d of phosphorus load over a period of 60 days in 18 patients with mild CRI with a bone biopsy showing ABD (n = 7) or with low serum PTH (serum intact PTH < or = 40 ng/l) and serum phosphorus < 4.5 mg/dl (n = 11). RESULTS: Serum intact PTH increased significantly only after 1 g of phosphorus (58.5 to 83 ng/l) with a median percent increase of 72%. PTH secretion increased more in patients with lower basal PTH levels (81%). Serum phosphorus did not change significantly and urinary phosphorus increased from 487 to 1,062 mg/dl (p < 0.05). Significant decreases in serum ionized calcium (from 1.26 to 1.19 mmol/l) and calcitriol (from 34.5 to 24.9 pg/ml) were observed. Changes in PTH were inversely correlated with changes in serum ionized calcium (r = -0.54, p < 0.05) and the final PTH concentrations were positively correlated with changes in serum phosphorus (r= 0.52, p < 0.05). CONCLUSIONS: The parathyroid glands of chronic renal insufficiency patients with "relative hypoparathyroidism" or ABD responded to a phosphorus load with an increase in serum PTH levels. The decrease in serum ionized calcium and calcitriol as well as minimal changes in serum phosphorus appeared to be involved in this response.

Adult↗
PubMed1988

Calcium, phosphorus, and vitamin D requirements of infants receiving parenteral nutrition.

Calcium and phosphorus form the major inorganic constituents of bone and serve a vital role in cell function and cell metabolism. Metabolism of calcium, phosphorus, and vitamin D are intimately related and the requirement of these nutrients should take into account this relationship. For high-risk infants, the use of parenteral nutrition may be associated with disturbances in calcium, phosphorus, and vitamin D metabolism. Acute alterations in calcium and phosphorus metabolism, as reflected by excessively elevated or decreased concentrations of circulating calcium and phosphorus concentrations, are frequently iatrogenic in origin and may be minimized by attention to details of fluid, electrolyte, glucose, and other non-calcium, non-phosphorus nutrients. Calcium and phosphorus content up to 15 mM each (60 mg calcium and 46.5 mg phosphorus/dl) with a calcium:phosphorus ratio of 1.3 to 1 by weight or 1 to 1 by molar ratio, at average fluid intakes (approximately 120 ml/kg/day), are suitable to maintain calcium and phosphorus homeostasis. This stable metabolic milieu is reflected by normal and stable serum concentrations of 1.25 dihydroxyvitamin D, and normal and stable renal tubular reabsorption of phosphorus. A low content of vitamin D, 25 IU/dl, in the presence of calcium and phosphorus appears to be sufficient to maintain normal vitamin D status as reflected by the maintenance of normal serum 25 hydroxyvitamin D concentrations.

Calcium, Dietary↗
PubMed1988

Calcium and phosphorus homeostasis in very-low-birth-weight infants appropriate for gestational age fed human milk.

The concentrations of calcium and phosphorus and the activity of alkaline phosphatase in serum were evaluated in 42 very-low-birth-weight (VLBW) and 83 low-birth-weight (LBW) infants on the 7th, 21st, and 42nd day of life. 9 VLBW and 16 LBW infants were randomized for measurement of the renal excretion of calcium and phosphorus on the 3rd, 5th, 7th, 21st, and 42nd day of life during human milk feeding and 14 VLBW-infants fed human milk supplemented with 1 mmol NaH2PO4 per 100 ml. All serum parameters were found to be normal. Supplementation of human milk with NaH2PO4 leads to a tendency of higher concentrations of phosphorus than found in VLBW-infants exclusively fed with native human milk, but all differences between the two groups were not significant. VLBW-infants appeared more than LBW-infants to be conserving phosphorus and wasting calcium during human milk feeding. Supplementation of human milk with NaH2PO4 results in higher phosphorus lower calcium excretion in urine of VLBW-infants, but they do not reach the values of LBW-infants. Because the activity of alkaline phosphatase was not different between the feeding groups and in all cases within the normal range a delayed bone mineralisation cannot be assumed in the infants studied. Thus, the phosphorus deficiency which is shown by the renal excretion of calcium and phosphorus in the VLBW-infants can be considered to be latent. In the light of our data the concentration of phosphorus in human milk seems to be too low and the calcium/phosphorus ratio too high for the optimal mineral metabolism in VLBW-infants. The supplementation used improves the situation, but the phosphorus intake seems still too low. Further investigations are needed to detect the optimal phosphorus intake for these infants. The calcium/phosphorus ratio in the urine is a good marker to estimate a latent phosphorus deficiency in VLBW-infants.

Alkaline Phosphatase↗
PubMed2000

Osteopenic disease in growing pigs: diagnostic methods using serum and urine calcium and phosphorus values, parathoromone assay, and bone analysis.

This research was performed to evaluate the utility of several serum and urine parameters as well as bone ash and plasma parathormone assay to diagnose and monitor diet-related osteopenia in growing pigs. Five diets were tested as follows: calcium-deficient, phosphorus-replete; moderate-deficiency of calcium and phosphorus; marked deficiency of calcium and phosphorus; calcium replete, phosphorus deficient; and vitamin D deficient. Parameters monitored included serum calcium and phosphorus as well as ratios of urine calcium to creatinine, phosphorus to creatinine, calcium to phosphorus, and percent fractional excretions of calcium and phosphorus. Plasma parathormone (PTH) levels were monitored in 2 of 3 experiments. Osteopenic bone differences at necropsy were evaluated by bone density, percent ash, ash per milliliter bone, calcium per milliliter bone, and phosphorus per milliliter bone. Marked change in urine mineral parameters, especially the calcium-to-phosphorus ratio, typically occurred within 1 to 2 days of treatment and preceded significant change in serum mineral or plasma PTH by 2 to 3 weeks. When monitored, plasma PTH levels were elevated following treatment, which confirms the hyperparathyroid state induced by the test diets. Significant differences in bone mineralization between control and treatment diets at necropsy were generally observed. The results of this study indicate that the analysis of urine minerals offers an early, noninvasive technique to investigate diet-associated osteopenic disease in growing pigs, which can be supported further by bone mineral analysis at postmortem using techniques herein described. Several urine mineral reference intervals for application to field investigations are included. Research into application of similar techniques to evaluate calcium and phosphorus homeostasis in pigs of all ages, including gestating and lactating gilts and sows, appears warranted.

Animal Feed↗
PubMed2003

Co-dependence of calcium and phosphorus for growth and bone development under conditions of varying deficiency.

The purpose of this study was to quantify the effect of variation in calcium intake, with and without supplemental phosphorus, on growth and bone development in growing animals under conditions of varying calcium and phosphorus deficiency. Nine groups of weanling male rats were fed a diet nutritionally complete, except for calcium and phosphorus, for 28 days. This diet provided nine levels of varying calcium and phosphorus repletion, using either calcium carbonate, dicalcium phosphate, or tricalcium phosphate. Body weights and diet consumption were measured throughout the test period. At term, the femurs from each animal were weighed, measured for tensile strength, bone mineral content (BMC), and bone density, and analyzed for ash, calcium, phosphorus, and histology. As expected, at equivalent levels of calcium supplementation, the two phosphorus-containing salts promoted significantly greater improvement in all the bone variables measured, as well as greater body weight gain and diet and calcium utilization, compared to animals supplemented with calcium only. Histomorphometric analysis confirmed the results of the mineral analysis and showed the structural impact of the inadequate mineral intake. The mean values for ash weight, BMC, and tensile strength in the nine diet groups were well fit (R(2) values ranging from 0.93 to 0.99) by multivariate models incorporating only the diet content values for calcium and phosphorus. In these models, the value for the phosphorus coefficient was three to sixfold larger than that for the calcium term, indicating a substantially greater effect of varying phosphorus intake than of varying calcium. These results demonstrate both the co-dependence of calcium and phosphorus in bone development and the importance of providing both minerals to support soft tissue and bone growth.

Animals↗
PubMed1995

Age at sexual maturity influences the response of single comb White Leghorn pullets to marginal and low levels of dietary phosphorus.

This study was designed to determine the differences in response of early-maturing (EM) and late-maturing (LM) Single Comb White Leghorn pullets within a flock to marginal or low dietary phosphorus. Various levels of dietary phosphorus were fed to EM and LM Leghorn pullets from 18 wk of age until the age of peak egg production (24 wk). The dietary phosphorus levels were 0.40, 0.45, 0.50, 0.55 and 0.70 g total phosphorus (tP)/100 g diet, corresponding to calculated available phosphorus values of 0.18, 0.23, 0.28, 0.33 and 0.48 g/100 g, respectively. At 0.70 and 0.55 g tP/100 g, the plasma inorganic phosphorus, Ca++ and urine calcium concentrations did not differ between EM and LM pullets, whereas LM pullets had a better bone status than EM pullets as reflected by bone mineral content, bone density and bone breaking strength. As dietary phosphorus was lowered from 0.55 to 0.4 g tP/100 g, the plasma concentration of inorganic phosphorus dropped and that of Ca++ increased at greater rates in LM pullets than in EM pullets. The magnitude of decline in bone status was also greater in LM than in EM pullets when dietary phosphorus was lowered from 0.55 to 0.40 g tP/100 g. The maximum incidences of osteoporosis and mortality were observed in LM pullets fed 0.40 g tP/100 g followed by LM pullets fed 0.45 g tP/100 g diet. We conclude that when early layer diets contain marginal or low levels of phosphorus, the severity of adverse effects are greater in LM pullets than in EM pullets.

Aging↗
PubMed1997

Biological evaluations of commercial dicalcium phosphates as sources of available phosphorus for broiler chicks.

One thousand male Hubbard chicks were used in a 21-d study (10 birds per battery cage) to determine relative biological availability of phosphorus in seven samples of commercial dicalcium phosphate, expected to contain variable amounts of monocalcium phosphate. Five samples were from established producers in Brazil and two from the U.S. Pure calcium phosphate dibasic dihydrate was used as the reference standard. Phosphates were added to the corn-soybean basal diet (22.5% CP; 0.4% total phosphorus) to provide 0.1, 0.2, and 0.3% supplemental phosphorus. The calcium level was 1.0% for all diets. Left tibias were removed for bone ash (BA) and bone strength (BS) determination. Body weight, feed intake (FI), BA, BS, and plasma phosphorus increased (P < 0.01) and plasma calcium and alkaline phosphatase decreased (P < 0.01) with increasing dietary phosphorus regardless of source. The availability of phosphorus for each test phosphate was determined by slope ratio, with BW, BA, and BS regressed on phosphorus added within each phosphorus source. A relative biological value (RBV) was calculated based on BW, BA, and gain:feed ratio. Availability based on BW ranged from 97.07 to 110.41%. When BA was the criterion, values were 80.32 to 107.84% and for BS were 79.34 to 110.52%. The RBV ranged from 97.55 to 100.60%. Phosphate sources did not vary greatly in phosphorus availability. Overall phosphorus availability averages were higher for BW (103%) and RBV (99%) and lowest for BA (96%) and BS (94%).

Alkaline Phosphatase↗
PubMed2005

Mapping of QTLs for lateral root branching and length in maize (Zea mays L.) under differential phosphorus supply.

Low phosphorus availability is a primary constraint for plant growth in terrestrial ecosystems. Lateral root initiation and elongation may play an important role in the uptake of immobile nutrients such as phosphorus by increasing soil exploration and phosphorus acquisition. The objective of this study was to identify quantitative trait loci (QTLs) controlling lateral root length (LRL), number (LRN), and plasticity of the primary seedling root of maize under varying phosphorus availability. Using a cigar roll culture in a controlled environment, we evaluated primary root LRL and LRN at low and high phosphorus availability in 160 recombinant inbred lines (RILs) derived from a cross between maize genotypes B73 and Mo17, which have contrasting adaptation to low phosphorus availability in the field. Low phosphorus availability increased LRL by 19% in Mo17, the phosphorus-efficient parent, but significantly decreased LRL in B73, the phosphorus-inefficient genotype. Substantial genetic variation and transgressive segregation for LRL and LRN existed in the population. The plasticity of LRL ranged from -100% to 146.3%, with a mean of 30.4%, and the plasticity of LRN ranged from -82.2% to 164.1%, with a mean of 18.5%. On the basis of composite interval mapping with a LOD threshold of 3.27, one QTL was associated with LRN plasticity, five QTLs were associated with LRL and one QTL was associated with LRN under high fertility. Under low fertility, six QTLs were associated with LRL and one QTL with LRN. No QTLs were detected for plasticity of LRL. A number of RILs exceeded Mo17, the phosphorus-efficient parent, for LRL, LRN, and plasticity. The detection of QTLs for these traits, in combination with the observation of transgressive segregants in our population, indicates that favorable alleles can be combined to increase seedling lateral root growth in maize.

Breeding↗
PubMed2005

Variable responses of old-field perennials to arbuscular mycorrhizal fungi and phosphorus source.

If arbuscular mycorrhizal fungi (AMF) promote phosphorus partitioning of plant hosts, they could provide one mechanism for the maintenance of plant community diversity. We investigated whether AMF improved the ability of old field perennials to grow on a range of phosphorus sources and whether AMF facilitated differential performance of plant species on different phosphorus sources (phosphorus niche partitioning). We manipulated form of phosphorus (control versus different inorganic and organic sources) and AM fungal species (control versus four individual AMF species or an AMF community) for five old field perennials grown in a greenhouse in individual culture. Based on biomass after four months of growth, we found no evidence for phosphorus niche partitioning. Rather, we found that effects of AMF varied from parasitic to mutualistic depending on plant species, AMF species, and phosphorus source (significant Plant x Fungus x Phosphorus interaction). Our results suggest that the degree of AMF benefit to a plant host depends not only on AMF species, plant species, and soil phosphorus availability (as has also been found in other work), but can also depend on the form of soil phosphorus. Thus, the position of any AMF species along the mutualism to parasitism continuum may be a complex function of local conditions, and this has implications for understanding plant competitive balance in the field.

Biomass↗
PubMed2004

Bioavailability of phytic acid-phosphorus and magnesium from lentils (Lens culinaris m.) in growing rats: influence of thermal treatment and vitamin-mineral supplementation.

OBJECTIVE: We sought to improve the nutritive utilization of Lens culinaris M. variety vulgaris cultivar Magda-20 in growing rats by autoclaving the lentil seeds at 120 degrees C for 30 min at an internal pressure of 1 atm and by supplementing the rats with a vitamin-mineral premix. METHODS: Nutritional assessment was based on chemical analysis of total phosphorus, free phosphorus, phytate, magnesium, neutral detergent fiber, and acid detergent fiber contents of the lentils and the digestive and metabolic use of phosphorus and magnesium by the growing rats. RESULTS: The net absorption of phosphorus was greater than the amount of non-phytate phosphorus ingested by the animals fed diets of raw and autoclaved lentil flours. Vitamin-mineral supplementation of raw and autoclaved lentil flour resulted in a significant increase in dietary intake and net absorption of phosphorus and magnesium. For all of the experimental diets tested, there was a direct correlation between phosphorus or magnesium balance and weight gain (r = 0.91 and 0.80, respectively) and between phosphorus or magnesium balance and nitrogen balance (r = 0.91 and 0.87, respectively). CONCLUSIONS: Part of the phytate-phosphorus from raw and autoclaved lentil flour was available during digestion, and hardly any phytate was detected in the feces. Supplementation of raw lentil flour with a vitamin-mineral premix was the most effective treatment for increasing daily food intake, body weight gain, and nutritive use of phosphorus and magnesium.

Animals↗
PubMed2005

The effects of sediment size fraction and associated algal biofilms on the kinetics of phosphorus release.

Experiments using flumes containing sediment of three different size fractions, from two sites on the River Tame, investigated the influences of sediment particle size, and an associated biofilm, on sediment-water exchanges in heterogeneous sediment deposits. This is the first study undertaken to understand the kinetics of the release of soluble reactive phosphorus from sediments of natural systems to identify which of the size compartments affected those fluxes most. Samples of fine material (<2 mm), gravel (2-20 mm), and stones (>20 mm) were collected over a period of several weeks and brought to a fluvarium where they were placed in artificial, controlled flow, and flume channels. Synthetic solutions of similar ionic strength to the river were prepared using calcium chloride. Temperature, pH, and dissolved oxygen of the solution overlying the sediment were monitored automatically whilst filtered samples were obtained at 2 h intervals over 48 h. The biomass, expressed as mg m(-2) chlorophyll a, of the algal component of the biofilm from the surface of the sediment was estimated using methanol extraction. Differences in the responses were observed between the sediment size fractions and the two sites, where contaminant concentrations varied. The equilibrium phosphate concentration and a phosphorus transfer index were used to establish that there was a net uptake of phosphorus by all three sediment size fractions, from both sites, at the time of sampling. The kinetic results showed very fast initial reactions of phosphorus release from the larger size fractions with a well-developed filamentous algal growth present implying a different mechanism than diffusion being involved. The stones and associated biofilms also released more phosphorus than the fine fraction, e.g. final release concentrations for the most contaminated site were: fines approximately 2.5 microM, gravel approximately 6.5 microM, and stones approximately 65.0 microM (expressed as soluble reactive phosphorus). Phosphorus fluxes, calculated assuming the concentration of phosphorus in the sediment was less than the equilibrium concentration, were a maximum at the most contaminated site, e.g. fines 6.4 nmol m(-2) s(-1), gravel 27 nmol m(-2) s(-1), and stones 109 nmol m(-2) s(-1) (normalised with respect to the river bed area). These results confirm that sediment having a biofilm and associated particulate material results in a greater flux than fine sediment, which does not support a filamentous biomass. Removal of the fine particulates trapped in the algal growth reduced soluble phosphorus release. These factors demonstrate that both gravel and stone substrates have an important control over the release of soluble reactive phosphorus.

Biofilms↗
PubMed2005

Phosphorus-discharge hysteresis during storm events along a river catchment: the River Swale, UK.

Variations in the concentration of determinands in rivers during storms often result in a hysteresis effect with different concentration during the rising and falling limb of the hydrograph. This is investigated here by measuring total phosphorus, particulate phosphorus and soluble reactive phosphorus at 3-h intervals at three points along the River Swale. Phosphorus concentration-discharge hysteresis from 10 storm events were quantified using an empirical model. The size and direction of the hysteresis loops were described by a response factor, and the slope of the loop quantified by a gradient constant. The modelled loops produced acceptable agreement with the field measurements. Hysteresis patterns for all phosphorus fractions changed markedly downstream, with predominantly anticlockwise trajectories in the upland moors (indicating a slow diffuse phosphorus delivery to the river) and clockwise in the intensively farmed lowland (indicating mobilisation of within-channel and riverbank phosphorus, and rapid inputs from field drains). The size of the hysteresis loops increased downstream, indicating an increased capacity for phosphorus storage and mobilisation within the lower catchment. During a succession of storms, lowland hysteresis loops decreased in magnitude, tending towards anticlockwise behaviour, indicating a depletion of mobile phosphorus from the river channel and margins. The modelling of hysteresis trajectories offers a convenient method of determining the relative contributions of diffuse and within-channel phosphorus sources.

Agriculture↗