Effects of vitamin D on calcium regulation in vitamin-D-deficient pigs given a phytate-phosphorus diet

Dynamics of bone mineralization in primiparous sows as a function of dietary phosphorus and calcium during lactation

To maximize the efficiency of dietary P utilization in swine production, understanding the mechanisms of P utilization in lactating sows is relevant due to their high P requirement and the resulting high inorganic P intake. Gaining a better knowledge of the Ca and P quantities that can be mobilized from bones during lactation, and subsequently replenished during the following gestation, would enable the development of more accurate P requirements incorporating this process of bone dynamics. The objective was to measure the amount of body mineral reserves mobilized during lactation, depending on dietary digestible P and phytase addition and to measure the amount recovered during the following gestation. Body composition of 24 primiparous sows was measured by dual-energy x-ray absorptiometry 2, 14, 26, 70 and 110 days after farrowing. Four lactation diets were formulated to cover nutritional requirements, with the exception of Ca and digestible P: 100% (Lact100; 9.9 g Ca and 3.0 g digestible P/kg), 75% (Lact75), 50% without added phytase (Lact50) and 50% with added phytase (Lact50 + FTU). The gestation diet was formulated to cover the nutritional requirements of Ca and digestible P (8.2 g Ca and 2.6 g digestible P/kg). During the 26 days of lactation, each sow mobilized body mineral reserves. The mean amount of mobilized bone mineral content (BMC) was 664 g, representing 240 g Ca and 113 g P. At weaning, the BMC (g/kg of BW) of Lact50 sows tended to be lower than Lact100 sows (-12.8%, linear Ca and P effect × quadratic time effect) while the BMC of Lact50 + FTU sows remained similar to that of Lact100 sows. During the following gestation, BMC returned to similar values among treatments. Therefore, the sows fed Lact50 could recover from the higher bone mineral mobilization that occurred during lactation. The P excretion was reduced by 40 and 43% in sows fed Lact50 and Lact50 + FTU, respectively, relative to sows fed Lact100. In conclusion, the quantified changes in body composition during the lactation and following gestation of primiparous sows show that bone mineral reserves were mobilized and recovered and that its degree was dependent on the dietary P content and from phytase supplementation during lactation. In the future, considering this potential of the sows' bone mineralization dynamics within the factorial assessment of P requirement and considering the digestible P equivalency of microbial phytase could greatly limit the dietary use of inorganic phosphates and, thus, reduce P excretion.

Evaluation of calcium to phosphorus ratio in spot urine samples as a practical method to monitor phosphorus intake adequacy in sows

The objective of this study was to evaluate the reliability of using Ca to P ratio measured in spot urine samples to assess P intake adequacy in gestating and lactating sows. A total of 36 sows were fed one of six concentrations of dietary total P (0.40%, 0.48%, 0.56%, 0.64%, 0.72%, and 0.80%) from day 7.5 ± 1 after breeding until the end of lactation (day 26.6 ± 1). Dietary Ca to P ratio was maintained constant across treatments at 1.25:1. Total 24-h urine samples were collected in mid- and late gestation (days 77.1 ± 2 and 112.4 ± 1), and early and late lactation (days 4.5 ± 1 and 18.2 ± 1). In parallel to 24-h collections, spot urine samples were collected at three different times (early morning, late morning, and late afternoon) in late gestation and late lactation. Urine Ca and P concentrations were measured and Ca to P ratio was calculated. Sows were classified as P-adequate or P-deficient according to dietary P intake. Urine Ca to P ratio was greater in sows fed P-deficient diets than sows fed P-adequate diets (P < 0.001). Receiver operating characteristic (ROC) curves were used to determine the cutoff values for urine Ca to P ratio to predict P intake adequacy. Three different categories of P intake were defined according to urine Ca to P ratio: deficient, adequate, and excessive. The area under the ROC for Ca to P ratio was 0.88 (95% CI 0.81 to 0.95). Best cutoff value of urine Ca to P ratio was 1.5 (sensitivity 94% and specificity 68%) to identify sows fed P-deficient diets and 0.5 for P-excessive diets (sensitivity 82% and specificity 82%). A strong relationship between Ca to P ratio in 24-h and spot urine samples was determined (r = 0.93, P < 0.01), independent of physiological state and collection time of spot samples (adjusted-R2 = 0.86, P < 0.01). The degree of agreement between spot and 24-h urine for P intake adequacy, assessed by Cohen's weighted kappa analysis, was substantial (0.78, 95% CI 0.69 to 0.88). We conclude that urinary Ca to P ratio provides a reliable prediction of the adequacy of P intake in reproducing sows. Urinary Ca to P ratio measurements in random spot urinary offers a practical method to determine dietary P adequacy.

Oral antibodies to human intestinal alkaline phosphatase reduce dietary phytate phosphate bioavailability in the presence of dietary 1α-hydroxycholecalciferol

While it is well established that active vitamin D treatment increases dietary phytate phosphate utilization, the mechanism by which intestinal alkaline phosphatase (IAP) participates in phytate phosphate use is less clear. The ability of human IAP (hIAP) oral antibodies to prevent dietary phytate phosphate utilization in the presence of 1α-hydroxycholecalciferol (1α-(OH) D3) in a chick model was investigated. hIAP specific chicken immunoglobulin Y (IgY) antibodies were generated by inoculating laying hens with 17 synthetic peptides derived from the human IAP amino acid sequence and harvesting egg yolk. Western blot analysis showed all antibodies recognized hIAP and 6 of the 8 antibodies selected showed modest inhibition of hIAP activity in vitro (6 to 33% inhibition). In chicks where dietary phosphate was primarily in the form of phytate, 4 selected hIAP antibodies inhibited 1α-(OH) D3-induced increases in blood phosphate, one of which, generated against selected peptide (MFPMGTPD), was as effective as sevelamer hydrochloride in preventing the 1α-(OH) D3-induced increase in blood phosphate, but ineffective in preventing an increase in body weight gain and bone ash induced by 1α-(OH) D3. These studies demonstrated that orally-delivered antibodies to IAP limit dietary phytate-phosphate utilization in chicks treated with 1α-(OH) D3, and implicate IAP as an important host enzyme in increasing phytate phosphate bioavailability in 1α-(OH) D3 fed chicks.

A novel bile salts-lipase polymeric film-infused minitablet system for enhanced oral delivery of cholecalciferol

Few researchers have investigated the use of multiple physiological enhancers combined with synthetic carriers to augment delivery of nutraceuticals. The current work describes the development of an oral delivery system termed a bioactive association platform (BAP) capable of delivering nutraceutical actives from a formulation framework specifically for enhancing the in vitro and in vivo performance of model vitamin, cholecalciferol (Vitamin D₃). Synthesis of a novel triple vitamin minitablet and an optimized bile salt/lipase alginate-glycerin film provided unique oral components for inclusion in a BAP capsule. Component validation and physicochemical characterizations included comparative ex vivo permeability, chemical structure mapping, thermodynamic analysis and magnetic resonance imaging. In vitro dissolution studies of the BAP produced an area under the dissolution curve (AUC) for cholecalciferol release that was 28% greater than a conventional comparator product. A total of 84.01% of cholecalciferol was released from the BAP within 3 h versus only 59% from a comparator. Ex vivo permeation studies revealed superior cholecalciferol membrane diffusion from the triple vitamin minitablet BAP component. In vivo performance showed a greater mean change from baseline cholecalciferol to peak plasma levels (C_max) from the BAP compared to the comparator (55.66 versus 46.05 ng/mL). Cholecalciferol bioavailability was improved in vivo with an AUC_0-inf from the BAP that was 3.2× greater than the conventional product. The BAP was also superior at improving and maintaining serum levels of the main metabolite, 25-hydroxyvitamin D₃, compared to the conventional system. In vitro and in vivo results thus confirmed improvements in cholecalciferol dissolution, membrane permeability and plasma drug levels. The study results position the BAP as an ideal oral vehicle for enhanced delivery of cholecalciferol.

Quantitative relationships between standardized total tract digestible phosphorus and total calcium intakes and their retention and excretion in growing pigs fed corn-soybean meal diets

An experiment was conducted to determine the quantitative relationships between standardized total tract digestible P (STTD P) and total Ca intakes with their retention and excretion by growing pigs fed corn-soybean meal diets. Forty-eight crossbred barrows (BW = 22.7 ± 2.9 kg) were allotted to 1 of 8 diets, housed individually in pens for 3 wk, and then moved to metabolism crates and allowed 4 d for adaptation and 5 d for collection of urine and fecal samples. Eight corn-soybean meal diets were formulated for similar NE, fat, and AA concentrations but to increase the STTD P from 0.16 to 0.62% using monocalcium phosphate. Dietary treatments were formulated for a constant Ca:STTD P ratio (2.2:1). The STTD P intake increased (P < 0.001) from 64 to 242% of the daily requirement (4.59 g/d of STTD P). Fecal and total excretion of P and Ca were linearly associated with mineral intake (P < 0.001). Constant urinary P excretion of 0.03 g/d P was observed, but at 4.96 g/d of STTD P intake, the urinary P excretion increased (P < 0.001). In contrast, Ca excretion in urine decreased (P < 0.001) with Ca intake, but constant excretion of 0.40 g/d Ca was reached at 17.97 g/d of Ca intake. The daily intakes of STTD P and Ca moderately explained the variation in urinary excretion of P (R2= 0.41) and Ca (R2= 0.64). The absorption and retention of P increased linearly (P< 0.001) with dietary P intake, whereas absorption and retention of Ca showed a quadratic response (P < 0.001). Absorption and retention of P and Ca were highly predictable from the STTD P and Ca intakes, with of 0.87 and 0.90, respectively. The femur mineral content (FMC) increased by 2.71 g with STTD P intake (P < 0.001) but reached a plateau (29.54 g of FMC) at 8.84 g/d of STTD P intake. The FMC was highly predictable from the STTD P intake (R2 = 0.89). The FMC affected the urinary P excretion ( P< 0.01), but moderately (R2= 0.19) explained the variation in urinary P. In conclusion, constant excretion of P in urine was observed but excretion increased linearly at STTD P intake levels above the requirement for maximum growth of growing pigs. The FMC increased with STTD P intake, but a plateau was reached at a STTD P intake level above the requirement. Dietary STTD P was used for growth and accumulated in bones until a plateau was reached and excess was excreted in urine. The predictability of P and Ca excretion in urine from the dietary STTD P and Ca intakes was moderate.

Practical use of sevelamer in chronic kidney disease patients on dialysis in People's Republic of China

Hyperphosphatemia is a common complication of dialysis patients. Only 38.5% of Chinese dialysis patients met the Kidney Disease Outcomes Quality Initiative defined targets for serum phosphate. Sevelamer is a high molecular weight cationic hydrogel polymer that prevents absorption of dietary phosphate by binding it in the gastrointestinal tract. In Chinese trials, it was confirmed that sevelamer had better efficacy than calcium carbonate in terms of reducing the serum level of phosphorus and calcium-phosphate product. Sevelamer can also reduce the levels of lipid parameters and improve the micro-inflammatory state. When sevelamer was combined with other treatments, it elicited superior effects on calcium phosphorus metabolism, secondary hyperparathyroidism, and renal osteodystrophy. Combination treatment of sevelamer and traditional Chinese medicine has the unique advantage. However, sevelamer is associated with a high incidence of gastrointestinal adverse effects in Chinese patients. Although more effective, the practical use of sevelamer is not very common because it is expensive and not paid by medical insurance. This article provides a comprehensive review of the practical use of sevelamer in chronic kidney disease patients on dialysis in People's Republic of China.

Sevelamer hydrochloride binds phosphate released from phytate in chicks fed 1α-hydroxy cholecalciferol

OBJECTIVE

Hyperphosphatemia in animal models of human renal disease has been linked to increased risk of death. Phosphate binders (e.g., sevelamer hydrochloride) and plant-based, low phosphate diets are used to reduce dietary phosphate load; however, animal models show that treatment with active forms of vitamin D(3) (e.g., calcitriol, a renal disease therapy) renders plant phytate phosphate available for absorption. Using an established chick model, the effectiveness of sevelamer in preventing the apparent absorption of liberated phytate phosphate during active vitamin D use was investigated in two separate experiments.

DESIGN

One-day-old chicks were fed ad libitum a basal diet containing deficient levels of inorganic phosphate (0.13%), but adequate in total phosphate (0.40%, 0.23% as phytate phosphate), with or without the inclusion of sevelamer hydrochloride (a phosphate binder), available inorganic phosphate, or active vitamin D as 1α-(OH) D(3).

MAIN OUTCOME MEASURES

Plasma phosphate (mg/dL), total bone ash (%), and weight gain (g).

RESULTS

Adding inorganic phosphate (0.36%) or 1α-(OH) D(3) increased plasma phosphate 49% and 48%, respectively (P < .0001), and bone ash 23% and 19%, respectively (P < .001). The addition of 1% sevelamer to the basal diet with added inorganic phosphate or 1α-(OH) D(3) significantly decreased plasma phosphate by 28% and 20%, respectively (P < .01).

CONCLUSION

Active vitamin D increased the availability of phytate phosphate for intestinal absorption in an animal model; however, sevelamer effectively reduced the availability of phosphate liberated from phytate. These data imply that sevelamer has phytate phosphate binding efficacy.

Effect of diet composition on water consumption in growing pigs1

Concerns relating to use of water resources by the livestock industry, combined with the rising cost of manure management, have resulted in greater interest in identifying ways to reduce drinking water utilization by pigs while maintaining animal well-being and achieving satisfactory growth performance. The objective of this experiment was to determine if increasing the dietary CP or mineral concentrations increases water intake and excretion and, conversely, if reducing the dietary CP content reduces water intake and excretion. Forty-eight barrows (34.3 +/- 4.6 kg of BW; 12/treatment) were given free access to diets containing a low protein (16.9% CP), high protein (20.9% CP), or excess protein (25.7% CP) level, or a diet with excess levels of Ca, P, Na, and Cl. Water was available to each pig on an ad libitum basis via dish drinkers that were determined to waste less than 3% of total water flow. The excess CP diet tended to increase average daily water intake (ADWI) and urinary excretion (P < 0.10) and increased the water:feed ratio (P < 0.05); lowering dietary CP did not lower water intake or excretion. The excess mineral diet did not increase ADWI or urinary excretion but did increase water excretion via the feces. Daily nutrient intake and dietary nutrient concentration were poor predictors of ADWI; only daily intake of N and K were significantly correlated with ADWI (P < 0.05), and the r-values were low (0.39 and 0.32, respectively). There was no relationship between ADFI and ADWI. The average water:feed ratio was 2.6:1. Any study of water utilization is complicated by behavioral as well as nutritional and physiological influences, and isolating physiological need from so-called luxury intake is a significant experimental challenge. Because the impact of dietary treatment on water utilization was small, we conclude that factors other than dietary protein and mineral concentration and daily protein and mineral intake have a relatively large effect on water intake and excretion. Consequently, strategies to reduce water intake must recognize, understand, and manage these additional behavioral and physiological factors. Diet composition may be a part of strategies designed to reduce excessive water utilization by the pig industry but may have a limited effect if other important factors are ignored.

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.

Utilization of phytate phosphorus and calcium as influenced by microbial phytase, cholecalciferol, and the calcium: total phosphorus ratio in broiler diets

The present study was performed to evaluate the potential of microbial phytase and cholecalciferol (D3) for improving the utilization of phytate P and Ca and the influence of the Car:total (t) P ratio in a corn-soybean meal diet fed to broilers from hatch to 21 d of age. A 4 x 4 x 2 factorial arrangement of treatments was used: 1.1, 1.4, 1.7, and 2.0:1 Ca:tP ratio; 0, 300, 600, and 900 U of phytase/kg of diet; and 66 and 660 micrograms of D3/kg of diet. Another four treatments were included: the four Ca:tP ratios with 6,600 micrograms of D3 addition, but without phytase. Added phytase linearly increased (P < 0.001) BW gain, feed intake, toe ash content, and P and Ca retention; these measurements were negatively influenced by widening the dietary Ca:tP ratio, and synergetically improved by addition of D3. Increasing the Ca:tP ratio decreased (P < 0.001) all measurements in the presence or absence of supplemental phytase and D3. Dietary Ca:tP ratios between 1.1:1 to 1.4:1 appears critical to the efficient use of supplemental phytase and D3 for improving the utilization of phytate P and Ca. The addition of D3 in corn-soybean meal diets indicated a potential for improving the utilization of phytate P and Ca by increasing Ca and P retention by about 5 to 12% in birds, which led to an increase in toe ash content (P < 0.03). The enhanced phytate P utilization (P < 0.001) was also observed during assay of the phytase activity in the mixed diets with an addition of D3 and without added phytase. In summary, the findings of this study suggested that phytase, D3, and Ca:tP are important factors in degrading phytate and improving phytate P and Ca utilization in broilers.

Binding properties of goat intestinal vitamin D receptors as affected by dietary calcium and/or phosphorus depletion

The binding capacity (Bmax) and the affinity (Kd) of the intestinal vitamin D receptor (VDR) have been studied using mucosa preparations from the duodenum, jejunum and proximal colon of male growing goats which had been kept in a two-factorial (2 x 2) trial on Ca and/or P deficient diets for 9 weeks. This treatment resulted in significant changes of different parameters of Ca and P homeostasis. Irrespective from the level of Ca intake, P depletion caused significant hypophosphatemia with corresponding hypercalcemia. In both Ca depleted groups the calcitriol concentrations in plasma significantly increased by more than 100% in comparison with normal Ca supply. No changes were recorded for plasma calcitriol concentrations in response to P depletion with an adequate Ca supply. Plasma PTH levels were only increased significantly in Ca depletion with adequate P supply. Irrespective of different feeding regimens, the highest Bmax values were found in the jejunum. In all intestinal segments tested, the Bmax values were significantly decreased by P depletion as compared with an adequate P supply. No effects on the Bmax of VDR were observed in response to changes of Ca supply. The Kd values of the VDR were neither affected by different intestinal localizations nor by Ca and/or P depletion. From the present results, it has to be concluded that the physiological relevance of VDR down-regulation may not be related to P homeostasis rather than to Ca homeostasis by minimizing the hypercalcemia induced by P depletion.

Influence of exogenous porcine growth hormone on vitamin D metabolism and calcium and phosphorus absorption in intact pigs

The influence of growth hormone (GH) on vitamin D metabolism and calcium and phosphorus absorption in vivo is not clear. We, therefore, measured calcium and phosphorus balance, plasma 1,25-dihydroxyvitamin D (1,25(OH)2D), and intestinal vitamin D-dependent calcium-binding protein (CaBP 9k) in intact growing pigs given exogenous GH. Six 10-week-old pigs were given two daily subcutaneous injections of 50 micrograms porcine GH/kg body weight for 2 months; six control pigs were given vehicle. They were all fed a diet containing 1.1% Ca, 0.6% P, and 1000 IU vitamin D3/kg. Apparent Ca and P absorption and retention were measured in a 10-day balance trial at the end of the 2 months. The plasma levels of Ca, P, 1,25(OH)2D, IGF-I, and GH were determined, and the duodenal and jejunal mucosal CaBP 9k content was measured at slaughter. The plasma Ca and P of GH-treated pigs were unchanged, but all aspects of mineral metabolism, including the plasma 1,25(OH)2D concentration (40%), Ca absorption and retention (70%), P absorption (33%) and retention (45%), and jejunal CaBP 9k (40%), were stimulated, in addition to an increase in the circulating IGF-I concentration.

Effects of calcitriol on stimulation of ion transport in pig jejunal mucosa

1. Active sodium (Na+) and chloride (Cl-) fluxes were studied in vitro in Ussing-type chambers with stripped jejunal mucosa of piglets which suffered from pseudo-vitamin D deficiency rickets, type I. The piglets are devoid of renal calcitriol (1,25-dihydroxy vitamin D3) production and have only small amounts of calbindin in their jejunal enterocytes. 2. In the presence of 0.01 mM-indomethacin non-stimulated short-circuit current (Isc), transepithelial potential difference (PD), tissue conductance (Gt) and unidirectional Na+ (JNa) and Cl- fluxes (JCl) were not affected by the low calcitriol (LC) concentration in plasma. 3. Adding 10 mM-theophylline to the serosal solution in the presence of 0.01 mM-indomethacin caused significantly greater increases in Isc in LC mucosa than in mucosa of vitamin D3-treated and control piglets with normal calcitriol (NC) concentrations in plasma. Omission of indomethacin significantly increased Isc stimulation provoked by theophylline with LC and NC mucosa. The increase, however, was significantly greater with LC than with NC mucosa. 4. Omission of calcium (Ca2+) from the serosal bathing solution significantly depressed Isc stimulation by 10 mM-theophylline in indomethacin-treated LC and NC mucosa. But depression was greater with LC than with NC mucosa. 5. Blocking Ca2+ entry into the cytosol by adding either 0.1 mM-TMB-8 or 0.5 mM-d,l-verapamil to the serosal bathing solution abolished the difference in Isc response to theophylline between indomethacin-treated LC and NC mucosa due to greater depression of Isc in LC than in NC mucosa. 6. The combined effects of theophylline and A23187 on Isc stimulation were calcitriol dependent. In the presence of indomethacin this dependence was only significant when A23187 was given prior to theophylline. In the absence of indomethacin the combined effects of A23187 and theophylline on Isc were always significantly greater in LC than in NC mucosa, irrespective of the order of adding the two agents. 7. Addition of theophylline stimulated net Na+ and Cl- secretion in indomethacin-treated LC and NC mucosa. The increases of net Na+ and Cl- fluxes fully accounted for the rise of Isc with NC mucosa but accounted only partly for the increase in Isc with LC mucosa. This resulted in significant increase in theophylline-stimulated residual ion flux (JR) in LC mucosa which probably resulted from enhanced secretion of bicarbonate.(ABSTRACT TRUNCATED AT 400 WORDS)

Binding properties of duodenal 1,25-dihydroxyvitamin D3 receptors as affected by phosphorus depletion in lactating goats

1. Capacity and affinity of duodenal 1,25(OH)2D3 receptors were measured in P depleted goats and in control animals kept on an adequate P supply. Plasma concentrations of Pi, Ca and vitamin D3 metabolites and activity of plasma alkaline phosphatase were measured to characterize the effects of P depletion. 2. During P depletion plasma Pi concentrations decreased significantly whereas plasma Ca and alkaline phosphatase activity increased. No changes were recorded for plasma vitamin D3, 25OHD3 and 1,25(OH)2D3 concentrations. 3. P depletion resulted in a significant decrease of the equilibrium dissociation constant Kd of duodenal 1,25(OH)2D3 receptors without affecting the maximum binding capacity.