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A total of 360 pigs (DNA 600 × 241; initially 5.8 kg) were used in a 45-d growth study to evaluate the effects of adding 25(OH)D3 with 3 levels of standardized total tract digestible (STTD) P on nursery pig growth performance, bone and urine characteristics, and serum vitamin D. Pigs were weaned at 19 d of age and randomly allotted to 1 of 6 dietary treatments with 5 pigs per pen and 12 replications per treatment. Dietary treatments were arranged in a 2 × 3 factorial with main effects of 25(OH)D3 (0 or 50 µg/kg equivalent to 2,000 IU/kg of vitamin D3; Hy-D, dsm-firmenich, Plainsboro, NJ) and STTD P (70%, 100%, or 130% of the NRC [NRC 2012. Nutrient requirements of swine. 11th rev. ed. Natl. Acad. Press, Washington, DC) requirement estimate on a dietary percentage basis]. All diets contained 1,653 IU/kg of vitamin D3. On day 45, 1 pig per pen was euthanized to collect the right fibula, metacarpal, and 2nd and 10th ribs. Overall, increasing STTD P increased (quadratic, P ≤ 0.003) ADG, ADFI, and G:F with minimal improvement above 100% of the NRC STTD P requirement estimate. Added 25(OH)D3 had no effect on growth performance. Increasing STTD P decreased urinary Ca concentration (linear, P < 0.001) and increased urinary P concentration (quadratic, P < 0.001). When pigs were fed added 25(OH)D3, serum 25(OH)D3 increased (quadratic, P = 0.005) as STTD P increased but no differences were observed when 25(OH)D3 was not added and STTD P increased (25(OH)D3 × STTD P interaction, P = 0.032). When pigs were fed 25(OH)D3, serum 1,25(OH)2D3 increased (quadratic, P < 0.001) as STTD P decreased but the increase was not significant when no 25(OH)D3 was fed (STTD P × 25(OH)D3 interaction, P = 0.002). Bone ash percentage and weight increased (quadratic, P ≤ 0.065) in all bones as STTD P increased. Added 25(OH)D3 had no effect on bone density or bone ash weight; however, the reduction in bone ash percentage observed with reducing STTD P level tended to be less when 25(OH)D3 was provided (linear interaction, P = 0.098). Increasing STTD P decreased the likelihood of abnormal histologic bone lesions in the 10th rib. In summary, added 25(OH)D3 had limited effect on growth performance; however, an increase in serum concentrations of 25(OH)D3 and 24,25(OH)2D3 was observed. The addition of 25(OH)D3 to P-deficient diets increased percentage bone ash. Increasing STTD P to 100% of NRC [NRC 2012. Nutrient requirements of swine. 11th rev. ed. Natl. Acad. Press, Washington, DC] requirement estimate increased growth and 130% of NRC maximized bone ash., (© The Author(s) 2024. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

An experiment was conducted to determine the digestible calcium (Ca) and digestible phosphorous (P) requirements of 25 to 35-day-old broiler chickens. Fifteen corn-soybean meal-based diets containing 2.0, 2.5, 3.0, 3.5, and 4.0 g/kg standardized ileal digestible (SID) Ca and 2.5, 3.5, and 4.5 g/kg SID P were fed to broilers from d 25 to 35 post-hatch. Each experimental diet was randomly allocated to 6 replicate cages (8 birds per cage). Body weight and feed intake were recorded, and the feed conversion ratio was calculated. On d 35, birds were euthanized to collect the ileal digesta, tibia, and carcass for the determination of ileal Ca, and P digestibility, concentrations of ash, Ca, and P in tibia and the retention of Ca and P in the carcass. Titanium dioxide (5.0 g/kg) was included in all diets as an indigestible indicator for the ileal digestibility measurement. Feed intake and total excreta output were measured during the last 4 d of the experimental period for the measurement of apparent total tract retention of Ca and P. Fixed effects of the experiment were dietary concentrations of SID Ca and SID P and their interaction. If the interaction or main effects were significant (P < 0.05), the parameter estimates for second-order response surface model (RSM) were determined using General Linear Model procedure of SAS. The maximum response was not predicted for most of the parameters (including growth performance and tibia) as the Ca effect was linear which indicated that the highest level of Ca employed in the study may have not been high enough. The requirement of dietary SID Ca for maximization of these parameters, therefore, depends on the dietary SID P concentration when the dietary SID Ca is within 2.0 to 4.0 g/kg. However, based on the factorial analysis, the highest weight gain was observed at 3.5 g/kg SID P and 3.5 g/kg SID Ca concentrations. Tibia ash was higher in birds fed 4.5 g/kg SID P and was unaffected by dietary SID Ca concentrations. However, based on overall findings, a combination of 3.5 g/kg SID P and 3.0-3.5 g/kg SID Ca may be recommended for the optimum tibia ash. The recommended SID Ca requirements (at 3.5 g/kg SID P) for weight gain (3.5 g/kg or 6.4 g/kg total Ca) and tibia ash (3.0-3.5 g/kg or 5.5-6.4 g/kg total Ca) are lower than the current Ca recommendations (7.8 g/kg total Ca equivalent to 4.25 g/kg SID Ca; Ross, 2019) for broiler finishers, suggesting possible excess of Ca in diets formulated based on the current recommendation., Competing Interests: DISCLOSURES There is no conflict of interest., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

A total of 2,184 pigs (337 × 1,050, PIC; initially 12.4 ± 0.17 kg) were used in a 143-d study to evaluate the effects of feeding varying analyzed calcium to phosphorus ratios (Ca:P) at two standardized total tract digestible (STTD) phosphorus to net energy ratios (STTD P:NE). Pens of pigs (26 pigs per pen) were assigned to 1 of the 6 dietary treatments in a 2 × 3 factorial with main effects of STTD P:NE and Ca:P ratio. Diets consisted of two levels of STTD P:NE; High (1.80, 1.62, 1.43, 1.25, 1.10, and 0.99 g STTD P/Mcal NE from 11 to 22, 22 to 40, 40 to 58, 58 to 81, 81 to 104, and 104 to 129 kg, respectively); or Low (75% of the High levels), and three analyzed Ca:P ratios (0.90:1, 1.30:1, and 1.75:1). There were 14 pens per treatment. Diets were corn-soybean meal-based and contained a constant phytase concentration within each dietary phase with levels decreasing throughout the trial (phases 1 through 3, 500 FTU/kg, assumed release of 0.13% STTD P; phase 4, 400 FTU/kg, assumed release of 0.11% STTD P; phase 5, 290 FTU/kg, assumed release of 0.09% STTD P; and phase 6, 210 FTU/kg, assumed release of 0.07% STTD P). Overall, there was a Ca:P × STTD P:NE interaction (P < 0.05) observed for average daily gain (ADG), feed efficiency (G:F), final body weight (BW), hot carcass weight (HCW), bone mineral density, bone mineral content, and bone-breaking strength. When feeding Low STTD P:NE levels, increasing the analyzed Ca:P ratio decreased (linear, P < 0.001) ADG final BW, HCW, and tended to worsen G:F, bone mineral density, and bone mineral content (linear, P < 0.10). However, when feeding High STTD P:NE levels, increasing the analyzed Ca:P ratio significantly improved bone mineral content and bone mineral density (linear, P < 0.05), and tended to improve ADG and final BW (linear, P < 0.10) and G:F (quadratic P < 0.10). Additionally, increasing the analyzed Ca:P ratio worsened ADG, G:F, and bone mineralization with Low STTD P:NE but had marginal impacts when adequate STTD P:NE was fed., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

A total of 360 pigs (DNA 600 × 241, DNA; initially 11.9 ± 0.56 kg) were used in a 28-d trial to evaluate the effects of different bones and analytical methods on the assessment of bone mineralization response to dietary P, vitamin D, and phytase in nursery pigs. Pens of pigs (six pigs per pen) were randomized to six dietary treatments in a randomized complete block design with 10 pens per treatment. Dietary treatments were designed to create differences in bone mineralization and included: (1) 0.19% standardized total tract digestibility (STTD) P (deficient), (2) 0.33% STTD P (NRC [2012] requirement) using monocalcium phosphate, (3) 0.33% STTD P including 0.14% release from phytase (Ronozyme HiPhos 2700, DSM Nutritional Products, Parsippany, NJ), (4) 0.44% STTD P using monocalcium phosphate, phytase, and no vitamin D, (5) diet 4 with vitamin D (1,653 IU/kg), and (6) diet 5 with an additional 50 µg/kg of 25(OH)D3 (HyD, DSM Nutritional Products, Parsippany, NJ) estimated to provide an additional 2,000 IU/kg of vitamin D3. After 28 d on feed, eight pigs per treatment were euthanized for bone (metacarpal, 2nd rib, 10th rib, and fibula), blood, and urine analysis. The response to treatment for bone density and ash was dependent upon the bone analyzed (treatment × bone interaction for bone density, P = 0.044; non-defatted bone ash, P = 0.060; defatted bone ash, P = 0.068). Thus, the response related to dietary treatment differed depending on which bone (metacarpal, fibula, 2nd rib, or 10th rib) was measured. Pigs fed 0.19% STTD P had decreased (P < 0.05) bone density and ash (non-defatted and defatted) for all bones compared to 0.44% STTD P, with 0.33% STTD P generally intermediate or similar to 0.44% STTD P. Pigs fed 0.44% STTD P with no vitamin D had greater (P < 0.05) non-defatted fibula ash compared to all treatments other than 0.44% STTD P with added 25(OH)D3. Pigs fed diets with 0.44% STTD P had greater (P < 0.05) defatted second rib ash compared to pigs fed 0.19% STTD P or 0.33% STTD P with no phytase. In summary, bone density and ash responses varied depending on bone analyzed. Differences in bone density and ash in response to P and vitamin D were most apparent with fibulas and second ribs. There were apparent differences in the bone ash percentage between defatted and non-defatted bone. However, differences between the treatments remain consistent regardless of the analytic procedure. For histopathology, 10th ribs were more sensitive than 2nd ribs or fibulas for the detection of lesions., (© The Author(s) 2023. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The study evaluated the effects of dietary phosphorus supplementation on the fishmeal replacement with Clostridium autoethanogenum protein (CAP) in the diet of L. vannamei. Four isonitrogenous and isolipid diets were formulated: the PC diet contains 25% fishmeal, the NC, P1 and P2 diets were replaced 40% fishmeal with CAP and supplemented with 0, 0.8 and 1.6% NaH 2 PO 4 respectively (equivalent to dietary phosphorus level of 0.96%, 1.12% and 1.27%). Sampling and V. parahaemolyticus challenge test were conducted after 50-day-feeding (initial shrimp weight 1.79 ± 0.02 g). The results showed that there were no significant differences in the growth performance of shrimp among the 4 groups. The expressions of dorsal in the gut were significantly lower in shrimp fed the P1 and P2 diets than shrimp fed the NC diet and the expression of peroxinectin in the gut was lower in shrimp fed the NC diet than others. The cumulative mortality of shrimp after V. parahaemolyticus challenge was significantly lower in shrimp fed the P2 diet than those fed the NC diet. After the challenge, genes expressions related to the prophenoloxidase activating system (proPO, lgbp, ppaf) were inhibited in the hepatopancreas of shrimp fed NC diet but activated in shrimp fed the P1 diet compared to those fed the PC diet. The AKP and T-AOC activities were higher in shrimp fed the P2 diet than those fed the other diets. The thickness of muscle layer of shrimp fed the P1 diet was thicker than that in the other groups, and significant stress damage happened in the midgut of the shrimp fed the NC diet. The abundance of Pseudoalteromonas, Haloferula and Ruegeria in shrimp fed the P1 diet was higher than those fed the other diets, while Vibrio in shrimp fed the P2 diet was higher than those fed the other diets. This indicated that a low fishmeal diet with dietary phosphorus level of 1.12% could improve the histology, enhance immune response, and increase the abundance of beneficial bacteria in the gut of shrimp. The low fishmeal diet with dietary phosphorus level of 1.27% could improve disease resistance and antioxidant capacity, but there was a possibility of damage to the gut histology as well as increasing abundance of Vibrio in the gut microbiota of shrimp., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Fish meal is increasingly being replaced by plant protein raw materials, meanwhile, it brings phytic acid, which combines with phosphorus to form phytate phosphorus and leads to a low utilization rate of phosphorus in shrimp. To solve this problem, this study investigated the effects of phytase supplementation on growth performance, phosphorus utilization, antioxidants, and digestion in red swamp crayfish (Procambarus clarkii). Crayfish (initial mean weight: 8.69 ± 0.15 g, N = 324) were randomly divided into six groups each with three replicates of 18 individuals each, and hand-fed for 8 weeks with one of six experimental diets (50 and 490 g kg -1 animal and plant protein raw material, respectively): negative control (NC; 11.0 g kg -1 phosphorus), positive control (PC; 15 g kg -1 NaH 2 PO 4 added to NC; 14.7 g kg -1 phosphorus), and phytase supplementation diets (P1-P4: 0.1, 0.2, 0.4, and 0.6 g kg -1 phytase added to NC, respectively). The feeding trial was performed in a micro-flow water culture system. P2 showed a significantly higher weight gain rate (WGR), specific growth rate, protein efficiency ratio, and protein retention efficiency (PRE) but showed the lowest feed conversion ratio (FCR) than other groups. Broken-line regression analyses using WGR, FCR, and PRE as evaluation indices showed that the optimal dietary phytase supplementation level was 0.233, 0.244, and 0.303 g kg -1 , respectively. P2 showed the highest crude protein content of whole crayfish and abdominal muscle, and phosphorus deposition rate, which was significantly higher than that in NC and PC. P3 showed the highest calcium and phosphorus contents in whole crayfish and phosphorus content in abdominal muscle, and calcium and inorganic phosphorus content in serum, which were significantly higher than those in NC. P3 showed significantly lowest serum alkaline phosphatase, alanine aminotransferase, aspartate transaminase activities, malondialdehyde content in hepatopancreas, and highest catalase activity, which were significantly lower and higher, respectively, than those in NC and PC. In summary, the addition of 0.2-0.4 g kg -1 phytase significantly improves the growth performance, feed utilization, digestive enzyme activity, and antioxidant of P. clarkii, which has a similar effect to the direct addition of NaH 2 PO 4 at 15 g kg -1 to the feed., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The effect of a novel consensus bacterial 6-phytase variant (PhyG) on total tract digestibility (ATTD) of minerals and bone ash was evaluated in pigs fed diets containing medium- and high-solubility limestone (MSL and HSL, 69.6 and 91.7% solubility, respectively, at 5 min, pH 3.0) in a randomized complete block design. For each limestone, eight diets were formulated: an inorganic phosphate-free negative control (NC) based on wheat, corn, soybean-meal, canola-meal and rice-barn [0.18% standardized total tract digestible (STTD) P and 0.59% Ca]; the NC supplemented with 250, 500, 1,000, or 2,000 FTU/kg of PhyG, and; the NC with added monocalcium phosphate (MCP) and limestone to produce three positive controls (0.33, 0.27, and 0.21% STTD P, and 0.75, 0.70, and 0.64% Ca, respectively; PC1, PC2, PC3). In total, 128 pigs (12.8 ± 1.33 kg, 8 pigs/treatment, housed individually) were adapted for 16 d followed by 4 d of fecal collection. Femurs were collected from euthanized pigs on day 21. Data were analyzed by one-way ANOVA with means separation by Tukey's test, and by factorial analysis (2 x 4: 2 levels of limestone solubility, 4 STTD P levels, and 2 × 5: 2 levels of limestone solubility, 5 PhyG dose levels). Phytase dose-response was analyzed by curve fitting. A consistent negative effect of HSL on ATTD P and Ca was observed in control diets (P < 0.001). Across phytase-supplemented diets, HSL reduced (P < 0.05) ATTD Ca and P (% and g/kg) compared with MSL. Across limestones, increasing phytase dose level increased (P < 0.05) ATTD P exponentially. Limestone solubility had no effect on bone ash, but PhyG linearly increased (P < 0.05) bone ash; 500 FTU/kg or higher maintained bone ash (g/femur) equivalent to PC1. In conclusion, ATTD P and Ca were reduced by a high compared with a medium soluble limestone, but the novel phytase improved ATTD P and Ca independent of limestone solubility., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: The impact of dietary phosphorus (P) excess, especially on renal and cardiovascular health, has been investigated in several species, but little is known in dogs., Objective: The aim of this study was to examine effects of different P sources on concentration and postprandial kinetics of selected parameters of P homeostasis in dogs., Methods: Eight beagles received one control diet (P 0.5% dry matter [DM]) and three high P diets (poultry meal, NaH2PO4, and KH2PO4; P 1.7% DM) for 18d. Urine samples were collected pre- and postprandially while faeces were collected quantitatively for 5d and analysed for minerals. On day 18, blood was sampled 1h pre- and 0.5, 1, 1.5, 2, 3, 5 and 7h postprandially., Results: Pi (KH2PO4, NaH2PO4) but not organic P caused an increased apparent P digestibility and significantly influenced kinetics of serum FGF23, parathyroid hormone, P, CrossLaps and bonespecific alkaline phosphatase, demonstrating a disrupted calcium (Ca) and P homeostasis with potential harm for renal, cardiovascular and skeletal health., Conclusions: Results of feeding Pi to dogs indicate distinct disturbances of Ca and P metabolism, in contrast to organic sources. The use of Pi in food can therefore not be considered as safe. Further research, especially on dose and long-term effects, is warranted., Competing Interests: The authors have declared that no competing interests exist.

Phosphorus (P) is an integral part of diet formulation for broiler chickens as P is required for various biochemical processes essential to life. A study was designed to examine the additivity of apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of P in mixed diets containing corn and soybean meal (SBM) with or without phytase supplementation. Birds were fed a commercial starter diet from day 0 to 21 after hatching and then allotted to 7 dietary treatments in a randomized complete block design with the BW as a blocking factor. Four semipurified diets were prepared to contain corn or SBM as the sole source of P with or without the addition of phytase at 1,000 phytase units/kg of diet. Two mixed diets were also prepared to contain corn and SBM with or without the addition of phytase at 1,000 phytase units/kg diet. A P-free diet (PFD) was formulated to determine the basal ileal endogenous loss of P. There were 16 replicate cages of the PFD and 8 replicate cages of the 6 experimental diets, with 8 birds per replicate cage for a total of 512 birds. Diets were fed for 3 d. The ileal digesta of birds were collected from the distal two-thirds of the ileum on day 24 after hatching. The SID of P in corn and SBM were 52.2 and 65.4%, respectively (SEM = 1.37). The addition of phytase improved (P < 0.05) both the AID and SID of P in the corn, SBM, and mixed diets. The determined AID or SID in the corn and SBM with or without phytase was used to predict the AID or SID in the mixed diets. There were no differences between the predicted and determined digestibility values in the mixed diets for either AID or SID of P and thus additive. Phytase supplementation of the mixed diet did not influence the additivity of AID or SID. In conclusion, the AID or SID of P in the corn and SBM was additive in the mixed diets containing corn and SBM with or without the addition of phytase., (Copyright © 2020. Published by Elsevier Inc.)

Exogenous phytase supplementation increases P and Ca availability to allow for the dietary reductions without negative consequences on productivity or skeletal health. Effects of a Buttiauxella sp. phytase (BSP) supplemented in available P (avP)-reduced and Ca-reduced diets on performance, BW, eggshell quality, serum biochemical bone markers, and bone densitometry were evaluated in egg-laying hens from 68 to 78 wk of age. One hundred hens were fed 1 of 5 diets (n = 20/treatment), including a positive control (PC) with 0.35% avP and 3.5% Ca, and the PC moderately reduced in avP and Ca levels by 0.187 and 0.159% of the diet (by 53 and 4.5%), respectively, (NC1) or severely reduced by 0.231 and 0.275% of the diet (by 66 and 7.9%), respectively, (NC2). Other diets were the NC1 or NC2 supplemented with BSP at 600 FTU/kg (NC1 + BSP or NC2 + BSP, respectively). Egg production and feed conversion ratio were maintained by NC1 but were 11.9% lower and 12.3% higher, respectively, with the NC2 than the PC, which was alleviated by supplemental BSP. Diet effects on FI and eggshell quality followed a similar pattern. Body weight was 2.9% lower for NC1, and 6.1% for NC2 than the PC; BSP alleviated the decreased BW. Serum pyridinoline (bone resorption marker) was 20 to 27% higher in NC2 hens than in the other groups, with no effects on other bone markers. Total and trabecular space bone mineral density in the proximal metaphysis were 8.4 and 15.2% lower for NC1, respectively, and 12.1 and 26.7% lower for NC2, respectively, than PC. Supplemental BSP completely alleviated the decreased bone densitometry measures in NC1, but only partially in NC2. The NC1 hens maintained performance but had decreased BW and bone quality; phytase supplementation restored productivity, BW, and bone quality. The Ca and avP deficiencies in the NC2 hens relative to other groups were partially alleviated by the 600 FTU/kg BSP., (Copyright © 2020. Published by Elsevier Inc.)

Feeding strategies for growing monogastric livestock (particularly pigs) must focus on maximising animal performance, while attempting to reduce environmental P load. Achieving these goals requires a comprehensive understanding of how different P feeding strategies affect animal responses and an ability to predict P retention. Although along with Ca, P is the most researched macromineral in pig nutrition, knowledge gaps still exist in relation to: (1) the effects of P feed content on feed intake (FI); (2) the impact of P intake on body composition; (3) the distribution of absorbed P to pools within the body. Here, we address these knowledge gaps by gathering empirical evidence on the effects of P-deficient feeds and by developing a predictive, mechanistic model of P utilisation and retention incorporating this evidence. Based on our statistical analyses of published literature data, we found: (1) no change in FI response in pigs given lower P feed contents; (2) the body ash-protein relationship to be dependent upon feed composition, with the isometric relationship only holding for pigs given balanced feeds and (3) the priority to be given towards P retention in soft tissue over P retention in bones. Subsequent results of the mechanistic model of P retention indicated that a potential reduction in P feeding recommendations could be possible without compromising average daily gain; however, such a reduction would impact P deposition in bones. Our study enhances our current knowledge of P utilisation and by extension excretion and could contribute towards developing more accurate P feeding guidelines.

Dietary phosphorus (P) is essential for bone mineralisation in vertebrates. P deficiency can cause growth retardation, osteomalacia and bone deformities, both in teleosts and in mammals. Conversely, excess P supply can trigger soft tissue calcification and bone hypermineralisation. This study uses a wide range of complementary techniques (X-rays, histology, TEM, synchrotron X-ray tomographic microscopy, nanoindentation) to describe in detail the effects of dietary P on the zebrafish skeleton, after two months of administering three different diets: 0.5% (low P, LP), 1.0% (regular P, RP), and 1.5% (high P, HP) total P content. LP zebrafish display growth retardation and hypomineralised bones, albeit without deformities. LP zebrafish increase production of non-mineralised bone matrix, and osteoblasts have enlarged endoplasmic reticulum cisternae, indicative for increased collagen synthesis. The HP diet promotes growth, high mineralisation, and stiffness but causes vertebral centra fusions. Structure and arrangement of bone matrix collagen fibres are not influenced by dietary P in all three groups. In conclusion, low dietary P content stimulates the formation of non-mineralised bone without inducing malformations. This indicates that bone formation and mineralisation are uncoupled. In contrast, high dietary P content promotes mineralisation and vertebral body fusions. This new zebrafish model is a useful tool to understand the mechanisms underlying osteomalacia and abnormal mineralisation, due to underlying variations in dietary P levels.

The quality and strength of the skeleton is regulated by mechanical loading and adequate mineral intake of calcium (Ca) and phosphorus (P). Whole body vibration (WBV) has been shown to elicit adaptive responses in the skeleton, such as increased bone mass and strength. This experiment was designed to determine the effects of WBV and dietary Ca and P on bone microarchitecture and turnover. A total of 26 growing pigs were utilized in a 60-d experiment. Pigs were randomly assigned within group to a 2 × 2 factorial design with dietary Ca and P concentration (low and adequate) as well as WBV. The adequate diet was formulated to meet all nutritional needs according to the NRC recommendations for growing pigs. Low Ca, P diets had 0.16% lower Ca and 0.13% lower P than the adequate diet. Pigs receiving WBV were vibrated 30 min/d, 3 d/wk at a magnitude of 1 to 2 mm and a frequency of 50 Hz. On days 0, 30, and 60, digital radiographs were taken to determine bone mineral content by radiographic bone aluminum equivalency (RBAE) and serum was collected to measure biochemical markers of bone formation (osteocalcin, OC) and bone resorption (carboxy-terminal collagen crosslinks, CTX-I). At day 60, pigs were euthanized and the left third metacarpal bone was excised for detailed analysis by microcomputed tomography (microCT) to measure trabecular microarchitecture and cortical bone geometry. Maximum RBAE values for the medial or lateral cortices were not affected (P > 0.05) by WBV. Pigs fed adequate Ca and P tended (P = 0.10) to have increased RBAE max values for the medial and lateral cortices. WBV pigs had significantly decreased serum CTX-1 concentrations (P = 0.044), whereas animals fed a low Ca and P diet had increased (P < 0.05) OC concentrations. In bone, WBV pigs showed a significantly lower trabecular number (P = 0.002) and increased trabecular separation (P = 0.003), whereas cortical bone parameters were not significantly altered by WBV or diet (P > 0.05). In summary, this study confirmed the normal physiological responses of the skeleton to a low Ca, P diet. Interestingly, although the WBV protocol utilized in this study did not elicit any significant osteogenic response, decreases in CTX-1 in response to WBV may have been an early local adaptive bone response. We interpret these data to suggest that the frequency and amplitude of WBV was likely sufficient to elicit a bone remodeling response, but the duration of the study may not have captured the full extent of an entire bone remodeling cycle., (© The Author(s) 2019. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Hydroxyapatite, a mineral form of calcium (Ca) and phosphorus (P) that gives bones their rigidity, is the major and essential component of bones and teeth in the human and animal body. A suitable ratio of Ca and P is vital for bone growth. The aim of this study was to explore the effects of dietary calcium to available phosphorus ratios (Ca/AP) on bone metabolism and osteoclast activity of the osteoprotegerin (OPG)/receptor activator of nuclear factor kappa B ligand (RANKL) signalling pathway in piglets. At days 15 and 29, the piglets were assessed for growth performance, blood indicators, cytokines and the OPG/RANK/RANKL signalling pathway. Our results showed that piglets fed a dietary Ca/AP ratio of 2:1 increases growth performance and regulates blood indicators and cytokines (parathyroid hormone (PTH), calcitonin (CT), vitamin D 3 (VD 3 ) , insulin-like growth factor-1 (IGF-1), transforming growth factor-β (TGF-β), interleukin-1 (IL-1), interleukin-6 (IL-6), carboxyterminal propeptide of type I procollagen (PICP), tartrate-resistant acid phosphatase (TRACP), alkaline phosphatase (ALP) and osteocalcin (OCN) content). We also demonstrated that this ratio affects hormone secretion and further bone metabolism through the OPG/RANK/RANKL signalling pathway of osteoclasts. These results indicate that a suitable dietary Ca/AP ratio is vital for bone growth and reduce the incidence of bone diseases such as osteoporosis, providing a practical basis for the raising of piglets., (© 2019 Blackwell Verlag GmbH.)

Careful dietary management that reduces high phosphate intake is recommended to slow the progression of chronic kidney disease (CKD) and prevent complications of CKD and may help reduce chronic disease risks such as incident CKD associated with high phosphate intake in the healthy general population. For patients treated with maintenance dialysis, control of serum phosphorus levels is considered a marker of good care and requires a coordinated plan that limits dietary phosphate intake, uses oral phosphate binders, and provides an adequate dialysis prescription. Even with traditional thrice-weekly hemodialysis or peritoneal dialysis, use of phosphate binders, and a concerted effort to limit dietary phosphate intake, adequately controlled serum phosphorus levels are not possible in all dialysis patients. Efforts to limit phosphate intake are thwarted by the underestimated and unquantified phosphate content of processed foods and some medications due to the hidden presence of phosphate additives or excipients added during processing or drug formulation. Effectively limiting phosphate intake could potentially be achieved through simple US Food and Drug Administration regulatory actions. Mandatory labeling of phosphate content on all packaged foods and drugs would enable identification of healthy low-phosphate foods and medications and permit critically important control of total phosphate intake. Simple changes in regulatory policy and labeling are warranted and would enable better management of dietary intake of phosphate at all stages of kidney disease, as well as potentially reduced health risks in the general population., (Copyright © 2018 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

Objectives: Phosphorus ingestion with glucose was reported to stimulate the postprandial peripheral uptake of both phosphorus and glucose, a process that favors energy production. The aim of this study was to determine whether phosphorus ingestion with a meal can affect energy metabolism., Methods: Overnight fasted men (eight lean and seven obese) consumed a high-carbohydrate meal (648 kcal) with either placebo or phosphorus (500 mg) tablets in a random order. Energy expenditure and substrate oxidation were monitored for 240 min using ventilated hood indirect calorimetry., Results: Phosphorus ingestion with a meal increased the postprandial energy expenditure of both lean and obese individuals (P < 0.001), although in different patterns. Alterations in postprandial substrate oxidation was highly noticeable from time 120 min onward, where phosphorus-treated lean participants exhibited a significant decrease in respiratory quotient., Conclusion: Phosphorus ingestion with a high-carbohydrate meal alters postprandial energy metabolism mainly by enhancing postprandial energy expenditure that may ultimatly favor weight loss., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Phosphorus (P) is essential for building and maintaining a healthy and strong skeleton. Moreover, dietary P supply may play a role for bone turnover, and the excretion of bone turnover metabolites may be useful as markers for sufficient dietary P supply. The objective was to study the long-term effects of low, medium, and high dietary P supply on bone metabolism in terms of serum concentration and urinary excretion of bone turnover components and metabolites in healthy growing-finishing pigs compared with bone mineral content (BMC) and bone mineral density (BMD) of humerus and femur. Pigs were fed diets containing low [LP; 4.1 g/kg dry matter (DM)], medium (MP; 6.2 g/kg DM), or high dietary P (HP; 8.9 g/kg DM) from 39.7 kg body weight (BW) until slaughter at 110 kg BW. Urine and blood were collected at 40, 70, and 110 kg BW while bones were collected at slaughter. Serum was analyzed for osteocalcin (OC), bone alkaline phosphatase (BAP), and C-terminal telopeptides of type I collagen (CTX-I), whereas urine was analyzed for pyridinoline (PYD), deoxypyridinoline (DPD), CTX-I, hydroxylysine (HYL), galactosyl-hydroxylysine (GAL-HYL), glycosyl-galactosyl-hydroxylysine (GLC-GAL-HYL), and hydroxyproline (HYP). Humerus and femur were analyzed for BMC and BMD. The LP diet caused reduced OC and increased BAP and CTX-I concentrations in serum. Furthermore, BAP was increased in response to the HP diet. Urine metabolites of bone resorption were all increased in pigs fed the LP diet, but only a few responses were obtained in response to the HP diet. Furthermore, age-related decreases were identified for BAP, HYL, GAL-HYL, and GLC-GAL-HYL. Bone mineral content and BMD were markedly lowered in pigs fed the LP diet but were not affected in pigs fed the HP diet. In conclusion, OC, BAP, and CTX-I in serum have proved useful for P adequacy in growing-finishing pigs. In addition, urine bone resorption metabolites have also proved useful for P adequacy and analysis of PYD, DPD, and CTX-I was considered to be the most relevant markers due to their specificity for bone and their negative correlation with BMD, BMC, ash, calcium (Ca), and P contents. Finally, DPD may be the preferred marker in long-term P feeding assessments.

Intestinal phosphorus absorption is an important component of whole-body phosphorus metabolism, and limiting dietary phosphorus absorption is particularly of interest as a therapeutic target in patients with chronic kidney disease to manage mineral bone disorders. Yet, mechanisms and regulation of intestinal phosphorus absorption have not been adequately studied and discrepancies in findings exist based on the absorption assessment technique used. In vitro techniques show rather consistent effects of dietary phosphorus intake level and age on intestinal sodium-dependent phosphate transport. But, the few studies that have used in vivo techniques conflict with these in vitro studies. Therefore, we aimed to investigate the effects of dietary phosphorus intake level on phosphorus absorption using the in situ ligated loop technique in three different aged rats. Male Sprague-Dawley rats (n = 72), were studied at 10-, 20-, and 30-weeks-of-age on a low (0.1%), normal (0.6%), or high (1.2%) phosphorus diet in a 3x3 factorial design (n = 8/group). Rats were fed their assigned diet for 2-weeks prior to absorption testing by jejunal ligated loop as a non-survival procedure, utilizing 33P radioisotope. Metabolic cages were used for determination of calcium and phosphorus balance over the final four days prior to sacrifice, and blood was collected at the time of sacrifice for biochemistries. Our results show that phosphorus absorption was higher in 10-week-old rats compared with 20- and 30-week-olds and this corresponded to higher gene expression of the major phosphate transporter, NaPi-2b, as well as higher whole-body phosphorus balance and net phosphorus absorption. Dietary phosphorus intake level did not affect jejunal phosphorus absorption or NaPi-2b gene expression. Our results contrast with studies utilizing in vitro techniques, but corroborate results of other rodent studies utilizing in situ or in vivo methods. Thus, there is need for additional studies that employ more physiological methods of phosphorus absorption assessment., Competing Interests: I have read the journal's policy and the authors of this manuscript have the following competing interests: Colby Vorland has nothing to disclose. Pamela Lachcik has nothing to disclose. Loretta Aromeh has nothing to disclose. Dr. Moe reports personal fees from Amgen, grants from Chugai, grants from Keryx outside the submitted work. Dr. Chen has nothing to disclose. Dr. Hill Gallant reports grants from National Institutes of Health, grants from USDA NIFA Hatch Project, during the conduct of the study; grants from Chugai, personal fees from Sanofi-Aventis, outside the submitted work. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

The present study aimed to investigate the effect of low phosphorus diet with or without different levels of phytase enzyme supplementation on growth performance, body composition, nutrient retention efficiency, gene expression, and health status of A. hydrophila challenged fish. A total of 240 monosex males of Nile tilapia (Oreochromis niloticus) with an average body weight of 23.19 ± 0.15 g/fish were used. Fish were randomly chosen and divided into 4 equal groups (60 fish per group), with 3 subgroups containing 20 fish as a replicate. Group 1, was fed on a diet containing 100% P, group 2, was fed on a diet containing 50% P, group 3 and 4, were fed on low P with 500 or 1000 units of phytase/Kg respectively. It was observed that the 50% phosphorus diet significantly reduced body weight, feed intake, feed conversion ratio (FCR), and protein efficiency ratio (PER) compared to Nile tilapia fish fed on the diet containing 100% phosphorus. In contrast, fish fed on the diet containing 50% phosphorus supplemented by 500 or 1000 phytase units/kg significantly (P ≤ 0.05) increased final body weight (FBW), total body gain (TBG), average daily gain (ADG), and weight gain compared to Nile tilapia fed on the same diet or fed on the diet containing normal phosphorus without phytase supplementation. Different phosphorus and phytase supplementation levels had no significant effect on serum total protein, albumin, and globulin concentrations, meanwhile, phytase supplementation increased serum calcium and phosphorus levels. Nile tilapia fed on phytase supplementation had an increase in body protein, lipid content, and nutrient utilization efficiency compared to Nile tilapia fed on the diet containing 100% phosphorus. Nile tilapia fed on low dietary phosphorus showed an increase in mortality after infection and a decrease in phagocytosis and neutrophil compared to fish fed on normal phosphorus. Phytase supplementation, made immune response parameters return to its normal values and the pathological lesions of liver, spleen, stomach, and intestine were reduced. Moreover, normal phosphorus significantly up-regulated lipoprotein lipase (LPL) mRNA expression and down-regulated fatty acid synthase (FAS) mRNA in Nile tilapia's liver while low phosphorus with or without phytase supplementation reduced LPL expression and relatively up-regulated FAS., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Two studies were conducted to evaluate the growth performance and percentage bone ash of nursery pigs fed various combinations of Ca and P provided by inorganic sources or phytase. In Exp. 1, pens of pigs (n = 720, initially 6.1 ± 0.98 kg) were blocked by initial BW. Within blocks, pens were randomly assigned to one of six treatments (12 pens per treatment) in a three-phase diet regimen. Treatments were arranged in a 2 × 3 factorial with main effects of Ca (0.58% vs. 1.03%) and standardized total tract digestible (STTD) P (0.33% and 0.45% without phytase, and 0.45% with 0.12% of the P released by phytase). During treatment period, Ca × P interactions were observed for all growth criteria (P < 0.05). When diets had low Ca, pigs fed 0.45% STTD P with phytase had greater (P < 0.01) ADG and ADFI than those fed 0.33% or 0.45% STTD P without phytase. When high Ca was fed, ADG and ADFI were similar among pigs fed 0.45% STTD P with or without phytase and were greater than those fed 0.33% STTD P. Gain:feed was reduced (P < 0.01) when high Ca and low STTD P were fed relative to other treatments. On d 21, radiuses were collected from 1 pig per pen for bone ash analysis. Pigs fed 0.33% STTD P had decreased (P < 0.05) percentage bone ash than those fed 0.45% STTD P with or without phytase when high Ca was fed, but this P effect was not observed for low Ca diets (Ca × P interaction, P = 0.007). In Exp. 2, 36 pens (10 pigs per pen, initially 6.0 ± 1.08 kg) were used in a completely randomized design. Treatments were arranged in a 2 × 3 factorial with the main effects of STTD P (at or above NRC [NRC. 2012. Nutrient Requirements of Swine. 11th rev. ed. Washington (DC): National Academic Press.] requirement estimates) and total Ca (0.65, 0.90, and 1.20%). Experimental diets were fed during phases 1 and 2, followed by a common phase 3 diet. Diets at NRC (2012) P level contained 0.45% and 0.40% STTD P, compared with 0.56% and 0.52% for diets greater than the NRC (2012) estimates, in phase 1 and 2, respectively. During treatment period, increasing Ca decreased (linear, P = 0.006) ADG, but increasing STTD P marginally increased (P = 0.084) ADG, with no Ca × P interaction. When diets contained NRC (2012) P levels, pigs fed 1.20% Ca had decreased (P < 0.05) G:F than those fed 0.65% or 0.90% Ca; however, when high STTD P were fed, G:F was not affected by Ca (Ca × P interaction, P = 0.018). In conclusion, excess Ca decreased pig growth and percentage bone ash when diets were at or below NRC (2012) requirement for STTD P, but these negative effects were alleviated by adding monocalcium P or phytase to the diet.

The present study was conducted to investigate the postileal P digestion response of growing pigs to dietary P concentrations and sources. Twenty-four pigs (57.3 ± 1.9 kg initial BW) fitted with T-cannulas at the distal ileum were assigned to a duplicated 12 × 4 incomplete Latin square design with 12 diets and 4 periods. The 12 experimental diets consisted of 9 cornstarch-based diets using soybean meal (SBM), corn distiller's dried grains with solubles (DDGS), and canola meal (CM) as assay ingredients at 3 levels and 3 corn-SBM-based practical diets with 3 levels of dicalcium phosphate (DCP). Chromic oxide was included as an indigestible marker to calculate apparent ileal digestibility (AID), apparent total tract digestibility (ATTD), and apparent postileal digestibility (APID) of P. Each period consisted of 5 d of adaption period, 2 d of fecal samples collection, and 2 d of ileal digesta collection. The results showed that ileal P output, fecal P output, ileal digested P, total tract digested P, and the AID and ATTD of P were affected by the interaction of P concentrations and sources ( < 0.01). When pigs were fed the semipurified diets containing SBM and corn-SBM-based practical diets, the AID and ATTD of P increased with increasing dietary P level (linear, < 0.01). However, there were no linear or quadratic responses in the AID and ATTD of P for pigs fed diets containing increasing levels of CM and corn DDGS. Postileal digested P, the proportion of ileal digested P to total tract digested P, the proportion of postileal digested P to total tract digested P, APID of P, and hindgut disappearance of P were affected by dietary sources of P ( < 0.01). When pigs were fed the semipurified diets containing SBM and CM, there were no differences between the AID and ATTD of P. In contrast, the ATTD of P were greater than the AID of P for pigs fed diets containing corn DDGS and corn-SBM-based practical diets with DCP supplementation. In summary, postileal P digestion response of growing pigs was affected by dietary P sources.

A study was conducted to examine the effects of different dietary levels of available phosphorus (aP) on P excretion, bone mineralization, performance and the mRNA expression of sodium-dependent P transporters in growing pigs. Sixty-day old growing pigs (n = 54) with an average initial BW of 19.50 ± 1.11 kg were randomly allocated to a control diet (C) containing 0.23% available phosphorus (aP), T1 containing 0.17% aP and T2 containing 0.11% aP. There were 6 pens per treatment with 3 pigs per pen. Body weight and feed intake were measured weekly. At the end of each week, one pig from each pen was housed in a metabolic crate for 24 h to collect fecal and urine samples and then sacrificed to obtain third metacarpal (MC3) bones and jejunal and kidney samples. Bones were scanned by Dual Energy X-ray Absorptiometry (DEXA). Fecal and urine samples were sub-sampled and analyzed for P content. The expression of P transporter mRNA in jejunum and kidney samples was measured using quantitative real-time polymerase chain reaction (qRT-PCR). Data were analyzed using GLM procedure of the Statistical Analysis System (SAS Institute version 9.2). Pigs fed the T2 diet had reduced (P < 0.05) average daily gain (ADG) and gain to feed (G:F) compared to those fed the C diet during week 2. Overall, ADG and G:F were also reduced (P < 0.05) in pigs fed the T2 diet compared to those fed the C and T1 diets. Bone mineral density (BMD) and bone mineral content (BMC) were reduced (P < 0.05) in pigs fed the T2 diet compared to those fed the C diet throughout the experiment. At week 1, jejunal mRNA expression of Na (+)-dependent phosphate transporter 2 (SLC34A2) was increased (P < 0.01) in pigs fed the T2 diet compared to C diet. Renal mRNA expression of Na(+)-dependent phosphate transporter 1 (SLC34A1) and SLC34A3 were increased (P < 0.05) in pigs fed the T2 diet compared to those fed the C diet at week 2 and was accompanied by lower (P < 0.05) urinary P in pigs fed the T2 diet during week 2 and week 3. In conclusion, growing pigs are highly sensitive to low dietary P as shown by reduced ADG, bone mineralization and urinary P level, but moderate reduction in dietary P up to 0.17% aP in the diet has the potential to reduce environmental pollution by reducing P concentration in swine manure and without compromising performance.

Mutations in the renal sodium-dependent phosphate co-transporters NPT2a and NPT2c have been reported in patients with renal stone disease and nephrocalcinosis, but the relative contribution of genotype, dietary calcium and phosphate to the formation of renal mineral deposits is unclear. We previously reported that renal calcium phosphate deposits persist and/or reappear in older Npt2a-/- mice supplemented with phosphate despite resolution of hypercalciuria while no deposits are seen in wild-type (WT) mice on the same diet. Addition of calcium to their diets further increased calcium phosphate deposits in Npt2a-/-, but not WT mice. The response of PTH to dietary phosphate of Npt2a-/- was blunted when compared to WT mice and the response of the urinary calcium x phosphorus product to the addition of calcium and phosphate to the diet of Npt2a-/- was increased. These finding suggests that Npt2a-/- mice respond differently to dietary phosphate when compared to WT mice. Further evaluation in the Npt2a-/- cohort on different diets suggests that urinary calcium excretion, plasma phosphate and FGF23 levels appear to be positively correlated to renal mineral deposit formation while urine phosphate levels and the urine anion gap, an indirect measure of ammonia excretion, appear to be inversely correlated. Our observations in Npt2a-/- mice, if confirmed in humans, may be relevant for the optimization of existing and the development of novel therapies to prevent nephrolithiasis and nephrocalcinosis in human carriers of NPT2a and NPT2c mutations.

This study evaluated intake, microbial efficiency, and ruminal, small and large intestinal, and total digestibility of DM, OM, CP, and NDF, as well as availability of Ca, P, Mg, Na, K, Cu, Mn, and Zn in Zebu cattle fed with or without supplemental sources of Ca and P or a micromineral premix. Five rumen- and ileum-cannulated Nellore bulls (BW = 200 ± 10.5 kg; 9 mo) were used in the experiment, distributed in a 5 × 5 Latin square design. The experiment was developed in a 2 × 2 + 1 factorial design to measure the effects of mineral supplementation on intake, digestibility, and site of nutrient absorption. The factors consisted of 2 Ca and P levels (macromineral factor; CaP+ or CaP-) and 2 microminerals levels (micromineral factor; CuMnZn+ or CuMnZn-). In addition, a treatment with alimentary restriction (REST) was evaluated at 1.7% of BW. Nutrient fluxes were measured in the omasum and ileum, in addition to intake and fecal excretion. Microbial efficiency was estimated using purine derivative excretion. Dry matter, OM, NDF, CP intake, and total digestibility were not affected ( ≥ 0.058) by the absence of Ca, P, Cu, Mn, and Zn supplementation. Intake of Ca, P, and Mg were reduced ( < 0.01) by CaP-. The absence of CuMnZn reduced ( < 0.01) Cu, Mn, and Zn intake. Ruminal recycling of P, Na, and K is significant for increasing the influx of these minerals to the digestive tract; however, influences of treatments were not observed. The small and large intestines contributed to mineral absorption in different proportions ( < 0.05), according to minerals and treatments. Because of the similarity ( > 0.05) of OM, NDF, and CP digestion sites and coefficients, we assume that omitting supplemental sources of Ca, P, Cu, Mn, and Zn may be an option in raising cattle on feedlots. If supplementation is viable, knowledge about the specific absorption site of each mineral could positively impact choices about the supplemental source.

Weaned Nellore bulls ( = 36; 274 ± 34 kg) were used in a randomized block design with a 2 × 2 factorial arrangement of treatments to evaluate intake, fecal excretion, and performance with different concentrations of minerals. Experimental diets were formulated with 2 concentrations of Ca and P (macromineral factor; diet supplying 100% of Ca and P according to BR-CORTE () [CaP+] or diet without limestone and dicalcium phosphate [CaP-]) and 2 concentrations of microminerals (micromineral factor; diet with supplementation of microminerals [Zn, Mn, and Cu; CuMnZn+] or diet without supplementation of microminerals [Zn, Mn, and Cu; CuMnZn-]). The factor CaP- was formulated without the addition of limestone and dicalcium phosphate, and the factor CuMnZn- was formulated without inorganic supplementation of microminerals (premix). The diets were isonitrogenous (13.3% CP). Intake was individually monitored every day. Indigestible NDF was used as an internal marker for digestibility estimates. The bulls were slaughtered (84 or 147 d on feed), and then carcass characteristics were measured and liver and rib samples were collected. Feed, feces, rib bones, and liver samples were analyzed for DM, ash, CP, ether extract (EE), Ca, P, Zn, Mn, and Cu. There were no significant interactions ( ≥ 0.06) between macro- and micromineral supplementation for any variables in the study. Calcium, P, and micromineral concentrations did not affect ( ≥ 0.20) intake of DM, OM, NDF, EE, CP, TDN, and nonfiber carbohydrates (NFC). Calcium and P intake were affected ( < 0.01) by macromineral factor. Animals fed without Ca and P supplementation consumed less of these minerals. Dry matter and nutrient fecal excretion (OM, NDF, EE, CP, and NFC) were similar ( ≥ 0.23) among all factors. Performance and carcass characteristics were similar ( ≥ 0.09) among diets. The content of ash in rib bones was not affected by diets ( ≥ 0.06). Plasma P and phosphatase alkaline concentrations were similar ( ≥ 0.52) among diets. Supplementation of microminerals decreased ( < 0.01) plasma Ca concentration; nevertheless, all analyzed blood metabolites were within the reference values. Supplementation of Ca and P increased ( < 0.01) fecal excretion of these minerals. These results indicate that mineral supplementation (Ca, P, Zn, Mn, and Cu) of conventional feedlot diets for Nellore bulls may be not necessary. Dietary reductions in these minerals would represent a decrease in the cost of feedlot diets. Dietary reduction in Ca and P content cause a decrease in fecal excretion of these minerals, which, in turn, represents an opportunity to reduce the environmental impact of feedlot operations.

Two experiments were conducted to determine the apparent total tract digestibility (ATTD) and standardized total tract digestibility (STTD) of P in flaxseed meal (FM) and the effect of dietary microbial phytase on the digestibility of P in FM fed to growing and finishing pigs. In Exp. 1, eighteen growing barrows (26.6 ± 1.8 kg BW) were allotted to 1 of 3 experimental diets consisting of a diet containing 32% FM that was fed with or without phytase at 500 phytase units (FTU/kg and a P-free diet in a completely randomized design to give 6 replicates per diet. The experimental period lasted 12 d including first 7 d for adaptation and 5 d for total collection of feces. Pigs were fed their assigned diets at 4% of BW at the beginning of the experiment. The daily feed allowance was offered in 2 equal portions at 0800 and 1600 h. All experimental diets were provided in mash form. Results indicated that pigs fed the diets containing FM with dietary phytase had less ( < 0.05) fecal P concentration and daily P output than those fed the diets without phytase supplementation. Also, phytase supplementation increased ( < 0.05) the ATTD of P of the diets containing FM from 37.3% to 51.8% and STTD of P of the diets containing FM from 43.2% to 57.7%. The basal endogenous P losses (EPL) was calculated at 140 ± 11 mg/kg of DMI in growing pigs fed the P-free diet. In Exp. 2, eighteen finishing pigs (78.7 ± 2.4 kg BW) were randomly allotted to 1 of 3 dietary treatments. The experimental diets and procedures were similar to those described in Exp. 1. Similar to Exp. 1, pigs fed FM diets with phytase supplementation had less ( < 0.05) P concentration in feces than those fed diets without phytase supplementation. Also, daily P output was reduced ( = 0.08) when pigs were fed the FM diets with phytase compared to those fed the FM diets without phytase. The ATTD of P in FM diets was increased ( < 0.01) from 31.4% to 45.8%, whereas the STTD of P in FM diets was increased ( < 0.01) from 37.8% to 52.3% as a result of phytase supplementation. The basal EPL was calculated at 164 ± 19 mg/kg of DMI in finishing pigs fed the P-free diet. In conclusion, the ATTD and STTD of P in FM fed to growing pigs were 37.3% and 43.2%, respectively, whereas respective values for finishing pigs were 31.4%, and 37.8%, respectively. Also, dietary phytase supplementation improved both ATTD and STTD of P in FM for both stages of pigs by an average of 33%.

High dietary phosphorus (P) intake has acute negative effects on calcium (Ca) and bone metabolism, but long-term clinical data are contradictory. We hypothesized that high P intake is associated with impaired bone health as suggested by earlier short-term studies on bone metabolism. In this cross-sectional study, we investigated associations between dietary P intake, bone traits in the radius and tibia, and bone turnover in a population-based sample of 37- to 47-year-old Caucasian premenopausal women (n=333) and men (n=179) living in Southern Finland (60°N). We used various regression models in an "elaboration approach" to elucidate the role of P intake in bone traits and turnover. The addition of relevant covariates to the models mainly removed the significance of P intake as a determinant of bone traits. In the final regression model (P intake, weight, height, age, Ca intake, serum 25-hydroxyvitamin D, physical activity, smoking, contraceptive use in women), P intake was slightly positively associated only with bone mineral content and cross-sectional cortical bone area in the tibia of men. Among women, inclusion of Ca removed all existing significance in the crude models for any bone trait. In women P intake was negatively associated with the bone formation marker serum intact pro-collagen type I amino-terminal propeptide, whereas no association was present between P intake and bone turnover in men. In conclusion, these findings disagree with the hypothesis; P intake was not deleteriously associated with bone traits; however, P intake may negatively contribute to bone formation among women., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Increasing productivity and new housing standards necessitate a reevaluation of nutrient requirements for sows, including minerals. The objective of this study was to determine if the recommended levels of dietary Ca and P are adequate for sows housed in groups and that, therefore, have the potential for increased mobility. A total of 180 multiparous sows and gilts were assigned to 1 of 6 treatments. Treatments, arranged as a 3 × 2 factorial, included the main effects of dietary Ca:P-0.70:0.55% Ca:P (as-fed basis; control), 0.60:0.47% Ca:P (as-fed basis; Low CaP), and 0.81:0.63% Ca:P (as-fed basis; High CaP)-and housing-stalls or groups. The trial was initiated when sows were moved from the breeding stalls to the gestation room at wk 4 or 5 after breeding. Sows were initially fed 2.3 kg/d. This allotment was increased to 3.0 kg/d 2 wk prior to farrowing. Group-housed sows, fed in individual stalls, were allowed access to a loafing area after feeding. Serum samples were collected at the start of the trial and on d 100 of gestation, and both serum and milk samples were collected at mid lactation and prior to weaning. Neither diet nor housing had an effect on the total number of piglets born, ADG from birth to weaning, or weaning weight ( > 0.10). The number of live-born piglets and birth weight were unaffected by diet ( > 0.10) but were improved by group housing relative to stalls ( < 0.05). In late gestation, group-housed sows fed the Low CaP diet had reduced serum Ca (diet × housing interaction, = 0.02), and the greatest reduction (between d 28 and 100 of gestation) in serum P level was observed in group-housed sows fed the Low CaP diet (diet × housing interaction, = 0.04). Osteocalcin and pyridinoline, markers of bone formation and resorption, respectively, were unaffected by diet or housing ( > 0.10). Results from these studies imply that the level of dietary Ca and P recommended by the NRC is adequate for sows of modern genetics, whether housed in stalls or groups.

Improving the efficiency of P use by pigs is especially important for lactating sows, whose metabolic requirements for P and Ca are high. The effect of a sp. phytase on lactating sow performance and nutrient digestibility was investigated using the combined data set for 6 studies. Treatments included a nutritionally adequate positive control diet (PC), a negative control diet (NC; with an average reduction of 0.16% available phosphorous and 0.15% Ca vs. PC), and NC supplemented with a sp. phytase at 250, 500, 1,000 or 2,000 phytase unit (FTU)/kg, respectively. Phosphorus and Ca deficiency in the NC resulted in significantly higher BW loss compared with the PC. All phytase treatments maintained BW loss at the same level as the PC. Increasing doses of phytase significantly ( < 0.05) reduced sow BW loss and increased energy intake, with improvements most apparent in sows older than parity 5. The positive effects on BW and energy intake were not observed in first-parity sows. This may be a consequence of fewer first parity sows in the data set. The apparent total tract digestibility of DM, OM, and CP were not affected by phytase supplementation. Digestible P and Ca were significantly improved (linear, < 0.0001; quadratic, < 0.0001) by increasing the dose of phytase supplementation. Significantly lower apparent total tract digestibility of energy, Ca, and P was found in the NC treatment vs. the PC treatment, whereas no significant differences were found between phytase treatment and the PC treatment. In conclusion, phytase supplementation at a level of 250 FTU/kg can replace 0.16% available phosphorous and 0.15% Ca; however, increasing the phytase dose can further reduce BW loss in sows fed P- and Ca- deficient diets.

Although dietary phosphate restriction is important for treating hyperphosphatemia in patients with chronic kidney disease, it remains unclear whether a low-protein diet (LPD), which contains low phosphate, has beneficial effects on malnutrition, inflammation, and vascular calcification. The effects of LPD on inflammation, malnutrition, and vascular calcification were therefore assessed in rats. Rats were fed a normal diet or diets containing 0.3% adenine and low/normal protein and low/high phosphate. After 6 wk, serum and urinary biochemical parameters, systemic inflammation, and vascular calcification were examined. The protective effect of fetuin-A and albumin were assessed in cultured vascular smooth muscle cells. Rats fed the diet containing 0.3% adenine developed severe azotemia. LPD in rats fed high phosphate induced malnutrition (decreases in body weight, food intake, serum albumin and fetuin-A levels, and urinary creatinine excretion) and systemic inflammation (increases in serum tumor necrosis factor-α and urinary oxidative stress marker). LPD decreased the serum fetuin-A level and fetuin-A synthesis in the liver and increased serum calcium-phosphate precipitates. A high-phosphate diet increased aortic calcium content, which was enhanced by LPD. Reduced fetal calf serum in the medium of cultured vascular smooth muscle cells enhanced phosphate-induced formation of calcium-phosphate precipitates in the media and calcification of vascular smooth muscle cells, both of which were prevented by fetuin-A administration. Our results suggest that phosphate restriction by restricting dietary protein promotes vascular calcification by lowering the systemic fetuin-A level and increasing serum calcium-phosphate precipitates and induces inflammation and malnutrition in uremic rats fed a high-phosphate diet., (Copyright © 2015 the American Physiological Society.)

Vitamin D endocrine system is required for normal calcium and bone homeostasis. Trans-epithelial calcium absorption is initiated with calcium entry into the intestinal epithelial cells from luminal fluid through calcium permeable channels, and those expressions are strongly supported by vitamin D action. On the other hands, dietary treatment, mineral supplementation or restriction, successfully improves intestinal calcium absorption in global vitamin D receptor knock-out (VDR KO) mice, though vitamin D dependent active transport pathway is lacking. Dietary rescue of intestinal calcium absorption provided a positive calcium balance in this mouse model, and suggested that the major role of vitamin D function on calcium homeostasis was considered to be intestinal active absorption. To elucidate the entire process of intestinal calcium absorption, vitamin D independent calcium transport system was characterized into either trans-cellular or para-cellular process.

Crossbred pigs (n=720; average age=28±3 days and weight=9.5±0.3 kg) were used in a 20-day trial in order to determine the influence of phosphorus (P) source and various doses of pharmacological zinc (Zn) on growth performance, plasma minerals and mineral digestibility. Pigs (five intact males and five females per pen) were randomly allotted to treatments in a 3×3 factorial arrangement with three sources of dietary P (4.5 g/kg digestible P, 4.5 g/kg digestible P plus 2500 phytase units (FTU)/kg, or 5.5 g/kg digestible P) and three dietary levels of supplemental Zn (0, 1750 or 3500 mg/kg) from ZnO (82% Zn) with eight pens per treatment. Diets were formulated to exceed all nutrient requirements, including calcium (Ca), P and Zn from day 0 to 20. Zn supplementation increased (quadratic P<0.05) average daily feed intake. There was a significant Zn level×P source interaction on average daily gain and feed conversion ratio (FCR). Pigs fed 4.5 g/kg digestible P without or with 2500 FTU/kg phytase gained more per day (quadratic P<0.05) and had better FCR (quadratic P<0.05) when they were fed 1750 mg/kg supplemental Zn. However, pigs fed 5.5 g/kg digestible P gained more per day (linear P<0.05) and were more efficient (linear P<0.05) when they were fed 3500 mg/kg supplemental Zn. Plasma Zn and Zn digestibility increased (linear P<0.05) as pharmacological Zn supplementation increased from 0 to 3500 mg/kg, irrespective of P source. However, Ca, P, sodium (Na), potassium (K) and copper (Cu) digestibility were reduced (P<0.05) as pharmacological Zn supplementation increased, and this was mitigated or exacerbated by the supplementation of 5.5 g/kg digestible P or phytase. In conclusion, increasing the dietary inclusion of pharmacological Zn may impact growth performance in young pigs through the interaction with minerals such as Ca, P, Na and K. Pharmacological Zn may reduce Na or K digestibility and indirectly reduce water secretion into the lumen, resulting in an increase in faecal dry matter as pharmacological Zn supplementation in the diet increased.

The objectives of this experiment were to determine the apparent total tract digestibility (ATTD) and the standardized total tract digestibility (STTD) of P and the effect of microbial phytase on ATTD and STTD of P in full-fat rice bran (FFRB), defatted rice bran (DFRB), brown rice, broken rice, and rice mill feed when fed to pigs. Ninety-six barrows (initial BW of 19.4 ± 1.4 kg) were allotted to 12 diets with 8 replicate pigs per diet in a randomized complete block design. A basal diet based on corn and soybean meal was formulated. Five additional diets containing corn, soybean meal, and each rice coproduct were also formulated, and the ratio between corn and soybean meal in these diets was similar to that in the basal diet. Six additional diets that were similar to the initial 6 diets with the exception that 1,000 units of microbial phytase were added to the diets were also formulated. The ATTD and STTD of P were calculated for each diet using the direct procedure, and the ATTD and STTD of P in each rice coproduct were calculated using the difference procedure. Results of the experiment indicated that the concentration of P in feces was reduced (P < 0.05) from pigs fed diets with microbial phytase compared with pigs fed diets without phytase. No differences were observed between the basal diet and the broken rice diet, but the ATTD and the STTD of P in those diets was greater (P < 0.05) than in all other diets both without and with phytase. Among the rice coproducts, the greatest (P < 0.05) ATTD and STTD of P were observed for broken rice regardless of inclusion of phytase. If no microbial phytase was used, the values for STTD of P in brown rice, FFRB, DFRB, and rice mill feed were not different, but if microbial phytase was included in the diet, ATTD and STTD of P in brown rice was greater (P < 0.05) than in FFRB, DFRB, and rice mill feed. The STTD of P in brown rice, FFRB, and rice mill feed was greater (P < 0.05) if microbial phytase was used than if no microbial phytase was used. Addition of microbial phytase to the diets also increased (P < 0.05) the ATTD of Ca regardless of the rice coproducts used. In conclusion, the STTD of P is greater in broken rice than in all other rice coproducts. The STTD of P in brown rice, FFRB, DFRB, and rice mill feed is relatively low due to the high concentration of phytate in these ingredients, but addition of microbial phytase will increase the STTD of P in most rice coproducts.

There is increasing interest in dietary ingredients that are appropriate to support digestive and immune functions, but also maintain a stable microbial ecosystem in the gastrointestinal tract (GIT), particularly in weaned pigs. P is an essential nutrient for both microbes and their host, as it is involved, for example, in bone formation, energy metabolism, cellular signalling and stabilisation of cell membranes. Non-ruminant animals have limited access to phytate, the main storage form of P in plant seeds. The release of P bound to phytate requires phytase activity of plant or microbial origin, resulting in the formation of variable phosphorylated inositol phosphates (InsPs). The present review focuses on interactions between variations in dietary P supply, the immune system of the host, and the intestinal microbial ecosystem. Although results on the interaction between P and the immune system are inconsistent, several studies in different species have shown a positive impact of dietary P and phytase addition on the adaptive immune response. Recent studies with pigs suggest that P supply may influence intestinal microbial composition and activity. Individual InsPs or phosphate may also affect properties of pathogenic micro-organisms, such as metabolism or virulence. In conclusion, P may be considered as part of an integrated approach to support immune functions and maintain a stable microbial ecosystem in the GIT, thereby providing a barrier against potential pathogens. Within this regard, differences in phytate-P content and intrinsic phytase activity of plant feedstuffs, as well as the formation of individual InsPs, have to be taken into account.

The objective of this study was to estimate the independent associations between intake of phosphorus (P) and bone health parameters such as bone mineral content (BMC) and bone mineral density (BMD). It provides odds ratio (OR) of osteoporosis with quartiles of P intake adjusted for covariates (i.e., age, gender, BMI, and consumption of calcium (Ca), protein, total dairy foods, and vitamin D as well as intakes of supplemental Ca, vitamin D, and multivitamins/minerals). Data came from males and females aged 13-99 years who participated in the 2005-2010 National Health and Nutrition Examination Survey (NHANES). Analyses showed that higher P intake was associated with higher Ca intake, and that dietary Ca:P ratios (0.51-0.62, with a mean of 0.60 for adults) were adequate in all age/gender groups. High intake of P was positively associated with BMC in female teenagers (Q4 vs. Q1: BMC, 30.9 ± 1.1 vs. 29.0 ± 0.5 g, P = 0.001). It was also positively associated with BMC and BMD as well as reduced risk of osteoporosis in adults >20 years of age (Q4 vs. Q1: OR of osteoporosis, 0.55; 95% confidence interval [CI], 0.39- 0.79; P = 0.001; BMC, 37.5 ± 0.4 vs. 36.70 ± 0.3 g, P < 0.01; BMD, 0.986 ± 0.004 vs. 0.966 ± 0.005 g/cm(2), P < 0.05). The data suggest that high intake of P has no adverse effect on bone metabolism in populations with adequate Ca intake, and that it is also associated with positive bone parameters in some age/gender groups.

A better understanding of the fate of dietary P use by growing pigs will allow an optimization of P use and enhance sustainable practices. The optimization of P utilization is complicated by the multiple criteria, such as growth performance, bone mineralization, and manure P used for assessment of needs. Mathematical modeling is a useful tool to describe relevant biological mechanisms and predict relationships that describe the whole system behavior. Modeling allows development of robust multicriteria approaches to optimize P utilization, feeding cost, and manure application cost. This paper describes and evaluates a model developed to simulate the fate of dietary P, that is, to simulate its digestive and metabolic utilization through digestion, soft tissue, and ash modules. The digestion module takes into account the varied sources of dietary minerals including responses to microbial and plant phytase and Ca and P interactions and predicts absorption and fecal excretion. The soft tissue module simulates the growth of the protein and is based on InraPorc model principles. The ash module simulates the partitioning of absorbed Ca and P into the bone, protein, and lipid compartments as well as urinary excretion. Model behavior showed that the model was able to accurately represent the impact of Lys deficiency on P retention, of Ca and P imbalances, and of Ca and P depletion and repletion sequences. The model's prediction capabilities in simulating whole-body protein, Ca, P, and ash based on published data showed high accuracy, with a slope and intercept that did not differ from 1 and 0, respectively, and an error due to disturbance (ED; variance not accounted for by regression of observed on predicted values). The model's prediction capabilities in simulating balance trial data showed good accuracy for apparent total tract digestibility (ATTD) of P (observed = -0.77 + 1.06 predicted) and P retention coefficient (observed = -4.5 + 1.15 predicted) with an ED of 89% for both criteria. The model's prediction capabilities in simulating Ca ATTD and Ca retention coefficient are lower (ED of 88 and 28%, respectively). This model simulates body ash independently of body protein and accounts for the impact of past and current dietary Ca and P supply. That ability is essential for the real-time adaptation of mineral supplies to suit individual production objectives, which would contribute to the overall success of pig production.

Background: Hypophosphatemia in early lactating dairy cows has been implicated as primary cause for postparturient hemoglobinuria in cattle. Decreased availability of phosphorus has been proposed to reduce adenosine triphosphate synthesis of erythrocytes and thereby reduce osmotic resistance of these cells., Hypothesis/objectives: To study the effect of phosphorus depletion on the phosphate concentration ([Pi]) in plasma and erythrocytes and the osmotic resistance of erythrocytes and to determine the association between plasma [Pi] and erythrocyte [Pi]., Animals: Ten healthy midlactating dairy cows in their 3rd to 5th lactation., Methods: Prospective study. Dietary phosphorus depletion for 5 weeks followed by phosphorus supplementation. Plasma and erythrocyte [Pi] and erythrocyte osmotic resistance were measured. Four cows underwent continuous dextrose infusion at the end of phosphate depletion to exacerbate hypophosphatemia., Results: Dietary P depletion resulted in a marked decline of the plasma [Pi] from 4.1 ± 1.0 mg/dL to a nadir of 1.7 ± 0,5 mg/dL, but did not alter erythrocyte [Pi] or osmotic resistance. Similarly, dextrose infusion induced a decline of the plasma [Pi] from 2.4 ± 0.5 mg/dL to 1.5 ± 0.5 mg/dL, but had no effect on erythrocyte [Pi] or osmotic resistance., Conclusions and Clinical Importance: In cattle, marked hypophosphatemia induced by dietary P depletion was neither associated with a decline in erythrocyte [Pi] nor with decreased osmotic resistance of erythrocytes. Phosphorus depletion alone is therefore unlikely to cause intravascular hemolysis and the plasma [Pi] is an unreliable index for the intracellular [Pi] of erythrocytes., (Copyright © 2014 by the American College of Veterinary Internal Medicine.)

A 14-d experiment was conducted to study the effects of 2 dietary variables on efficacy of a 6-phytase from Citrobacter braakii on broiler growth performance and tibia mineralization. Diets were formulated with or without nutrient matrix values for phytase as negative or positive control (NC or PC, respectively) and with 2 Ca:total P (tP; 2:1 or 2.5:1). The diets were supplemented with 0, 1,000, or 2,000 phytase units (FYT)/kg, thus producing a 2 × 2 × 3 factorial arrangement. Birds and feed were weighed on d 7 and 21, and tibia bones were collected from all the birds on d 21. The main effects of nutrient matrix, Ca:tP, and phytase supplementation were significant (P < 0.05) for all the growth performance responses (except for G:F for which there was no effect of matrix). The Ca:tP × phytase and matrix × phytase interactions were significant (P < 0.05) for weight gain. In the PC diets, phytase increased weight gain (P < 0.05) relative to the control only in diets with 2,000 FYT/kg, whereas in NC diets weight gain increased (P < 0.01) only from 0 to 1,000 FYT/kg levels. Broilers consuming diets with 2.5:1 Ca:tP had lower (P < 0.05) tibia ash, whereas phytase increased (P < 0.01) tibia ash, Ca, P, and Zn but decreased (P < 0.01) tibia K. Phytase supplementation of diets with 2:1 Ca:tP increased (P < 0.05) tibia P in birds receiving 1,000 FYT/kg relative to the control with no further increase at 2,000 FYT/kg, whereas each level of phytase supplementation increased (P < 0.05) tibia P in the diets with 2.5:1 Ca:tP. It was concluded that the best response to lower phytase supplementation (1,000 FYT/kg) was in NC diets with narrow Ca:tP, whereas the best response to higher level of phytase supplementation (2,000 FYT/kg) was achieved in diets in PC diets with wide Ca:tP., (©2014 Poultry Science Association Inc.)

A 14-d broiler experiment was conducted to assess the effects of 2 dietary variables on efficacy of a bacterial 6-phytase from Citobacter braakii on nutrient and phytate P (PP) utilization. Diets were formulated with or without nutrient matrix values (matrix) for phytase as negative control (NC) or positive control (PC), respectively, and with 2 Ca:total P (tP) levels (2:1 or 2.5:1). The diets were supplemented with 0, 1,000, or 2,000 phytase units (FYT)/kg of diet, thus producing a 2 × 2 × 3 factorial arrangement. Excreta were collected on d 19 to 21 and ileal digesta on d 21. There was no 3-way interaction on digestibility of any nutrient. There was matrix × phytase (P < 0.01) interaction for Ca and DM digestibility and Ca:tP × phytase interaction (P < 0.05) for acid hydrolyzed fat and Ca and P digestibility. Prececal flow of Mn, Zn, and Na was greater (P < 0.05) in NC diets, whereas phytase increased (P < 0.05) prececal flow of Mg, Fe, Mn, and Zn but decreased (P < 0.05) prececal Na flow. Total tract PP disappearance and total tract Ca retention increased (P < 0.05) with phytase supplementation in diets with 2:1 Ca:tP, whereas there was no effect of phytase supplementation on PP disappearance or Ca retention in diets with 2.5:1 Ca:tP. Total P and Ca retention were reduced (P < 0.05) in PC and NC diets when Ca:tP increased to 2.5:1, but the depression was more pronounced in the NC diet. In addition, PP disappearance decreased (P < 0.05) with increasing Ca:tP in the PC diets, but there was no effect of widening Ca:tP on PP disappearance in NC diets. It was concluded from the current study that the effect of phytase supplementation on P utilization is reduced when diets contain adequate P as exemplified in the PC diets and that the negative impact of wide Ca:tP is more pronounced in diets with phytase matrix allowance as exemplified in the NC diets., (©2014 Poultry Science Association Inc.)

This study addresses the question of whether feeding rations rich in P for a period of up to 42 d induces a positive P balance in adult ponies. Biochemical bone markers and parathyroid hormone (PTH; intact as well as whole PTH) were measured to obtain clues as to the effect of P loading on bone metabolism. The experiment had a Latin square design. Each feeding period lasted 42 d, and there were 2 balance trials (ECP1 and ECP2) within each feeding period. Each balance trial lasted 10 d (ECP1: d 11 to 21; ECP2: d 33 to 42). Six ponies aged 2.5 to 7 yr were fed a control diet that provided P and Ca according to the requirement (Control diet: 54 mg Ca·kg BW(-1) · d(-1); 36 mg P · kg BW(-1) · d(-1)), a diet high in Ca and P (HCaHP diet: 146 mg Ca · kg BW(-1) · d(-1); 121 mg P · kg BW(-1) · d(-1)), and a diet with a high P level only and Ca fed to the requirement (HP diet: 54 mg Ca · kg BW(-1) · d(-1); 122 mg P · kg BW(-1) · d(-1)). When fed the Control diet, the ponies showed a zero P and Ca balance over the 42-d period. The HCaHP diet resulted in both P and Ca retention (about 2 g Ca and P/d; P < 0.05). Phosphorus retention (about 2 g P/d) alone was observed when ponies were fed the HP diet, but P retention was only different (P < 0.05) from the Control diet in ECP1. The excretion of P in urine was reduced by greater Ca intake (P < 0.05), and Mg absorption was reduced by high P intake (P < 0.05). Plasma P concentration was raised by high P intake. Plasma Ca levels were not affected by dietary treatment. The greater (P < 0.05) P retentions observed for the HCaHP diet during ECP1 and ECP2 and HP diet during ECP1 could not be explained by processes that could have been indicated by the bone markers or PTH values. It was concluded that dietary-P-induced retention of P in ponies does not seem to be associated with altered bone metabolism in this study.

Improving dietary P utilization without modifying pig performance is crucial for production sustainability. A feeding program comprising three 28-d phases (20 to 40, 40 to 70, and 70 to 100 kg) was used to feed 72 pigs with an initial BW of 20 kg. The ability of the pigs to modify the digestive and metabolic utilization of P when fed either a control (CON) diet or a low-P (LOW) diet providing 40% less digestible P with a constant Ca:digestible P was studied using different sequences of dietary P and Ca restriction (i.e., depletion [LOW]) and recovery (i.e., repletion [CON]), namely CON-CON-CON, CON-CON-LOW, CON-LOW-LOW, LOW-CON-CON, LOW-LOW-CON, and LOW-LOW-LOW. Bone mineral content (BMC) was measured in the lumbar region (L2-L4) by dual-energy X-ray absorptiometry at the beginning and end of each feeding phase. Total feces and urine were collected during phases 2 and 3. At the end of phase 1, BMC was lower in the LOW pigs than in the C pigs (29%; P < 0.001). During phase 2, the BMC gain was greater in the LOW-CON pigs than in the CON-CON pigs (16%; P < 0.001). During phase 3, the LOW-LOW-CON pigs absorbed 26% more Ca (P < 0.001) and retained 56% more BMC (P < 0.001) than the CON-CON-CON pigs did. Digestive and metabolic adaptations allowed the LOW-LOW-CON and LOW-CON-CON pigs to reach BMC similar to that of the CON-CON-CON pigs. These metabolic adaptations are promising, but practical applications of these results requires a better understanding of the underlying mechanisms to fine-tune the degree of depletion, pig age, and the duration of P and Ca depletion and repletion periods.

Temperature and nutrient availability are both hypothesized to affect organisms at the cellular and genomic levels. In this multigenerational study, Daphnia magna (D. magna) and Daphnia pulex (D. pulex) were maintained at high (20 °C) and low (10 °C) temperatures and nourished with phosphorus (P)-sufficient (50 μmol/L) and P-deficient (2 μmol/L) algae for up to 35 generations to assess the multigenerational impacts on genome size and nucleus size. Analysis by flow cytometry revealed significant increases in nucleus size for both species as well as genome size for D. magna in response to a low temperature. The degree of endoreplication, measured as cycle value, was species specific and responded to temperature and dietary composition. Under dietary P deficiency, D. magna, but not D. pulex, showed an apparent reduction in haploid genome size (C-value). These genomic responses are unlikely to reflect differences in nucleotide numbers, but rather structural changes affecting fluorochrome binding. While the ultimate and proximate causes of these responses are unknown, they suggest an intriguing potential for genomic responses that merits further research.

The trial was performed to investigate the effects of different concentrations of non-phytate phosphorus (nPP) in the starter and grower (with phytase inclusion) periods on carcass characteristics, organ weight and weekly variations of growth performance in the grower period. Seven hundred and twenty-day-old male broiler chickens were randomly assigned to 12 treatments in a completely randomized design. Chickens received two dietary treatments (4.5 g/kg and 6 g/kg nPP) in the starter (0-21 days) and six experimental diets (4 g/kg, 3.1 g/kg, 2.3 g/kg and 2.3 g/kg + 1000 FTU/Kg of feed phytase, 1.5 g/kg, 1.5 g/kg nPP + 1000 FTU/Kg of feed phytase) in the grower period (22-42 days). Results showed that phytase inclusion in the second and third weeks of grower period could increase feed intake significantly. Also, decrease in the concentrations of nPP to 1.5 g/kg caused to decline body weight gain markedly. Moreover, there is a significant difference between 4.5 g/kg and 6 + 4 g/kg nPP (starter+grower) and 1.5 g/kg nPP. Phytase inclusion increased carcass yield and declined liver weight significantly. Dietary treatment of 4.5 + 1.5 g/kg nPP enhanced heart and liver weight markedly. It is concluded that starter diets with increased concentration of nPP (6 g/kg nPP) had no beneficial effects on growth performance in the starter and grower period in the total (0-42 days). Also, it is possible to decrease nPP concentration of grower diets to 1.5 and 2.3 g/kg with and without phytase inclusion respectively., (Journal of Animal Physiology and Animal Nutrition © 2013 Blackwell Verlag GmbH.)

Oral phosphorus supplementation stimulates fibroblast growth factor 23 (FGF23) secretion; however, the underlying mechanism remains unclear. The aim of this study was to investigate the involvement of parathyroid hormone (PTH) in increased plasma FGF23 levels after oral phosphorus supplementation in rats. Rats received single dose of phosphate with concomitant subcutaneous injection of saline or human PTH (1-34) after treatment with cinacalcet or its vehicle. Cinacalcet is a drug that acts as an allosteric activator of the calcium-sensing receptor and reduces PTH secretion. Plasma phosphorus and PTH levels significantly increased 1 h after oral phosphorus administration and returned to basal levels within 3 h, while plasma FGF23 levels did not change up to 2 h post-treatment, but rather significantly increased at 3 h after administration and maintained higher levels for at least 6 h compared with the 0 time point. Plasma PTH and FGF23 levels were significantly lower in the cinacalcet-treated rats than in the vehicle-treated rats. Plasma phosphorus levels were significantly higher in the cinacalcet-treated rats than in the vehicle-treated rats at 2, 3, 4, and 6 h after oral phosphorus administration. Furthermore, rats treated with cinacalcet+human PTH (1-34) showed transiently but significantly higher plasma FGF23 levels at 3 h after oral phosphorus administration compared with cinacalcet-treated rats. These results suggest that oral phosphorus supplementation secondarily increases circulating FGF23 levels at least partially by stimulation of PTH secretion.

The objective of this study was to determine the true digestible P requirements of 20- to 40-kg pigs by the broken-line regression analysis of growth performance using 6 levels of true total-tract digestible P. In Exp. 1, 24 barrows (initial BW=25.2±1.0 kg) were used to determine the true total-tract digestibility (TTTD) of P in monocalcium phosphate using the regression method. The dietary treatments included a corn-soybean meal-based diet (2.96 g total P/kg) and 3 additional dietary treatments with incremental addition of 0.50 g P/kg through monocalcium phosphate. Limestone (37.2% Ca) was added to maintain a constant Ca to P ratio of 1.25 to 1 across all diets. A 5-d adjustment period preceded a 5-d total collection of feces. Ferric oxide was used as a marker to time the initiation and termination of fecal collection. In Exp. 2, 108 barrows and gilts (initial BW=20.1±1.2 kg) were used in a 3-wk growth performance trial. Monocalcium phosphate was added to a corn-soybean meal-based diet to set up 6 levels of TTTD-based digestible P, ranging from 1.31 to 4.64 g/kg of diet with increments of 0.67 g/kg digestible P. Limestone was added to maintain a constant Ca level across all diets. The results of Exp.1 showed that dietary P intake, fecal P output, digested P, and apparent total-tract digestibility of P increased linearly (P<0.05) with the increasing supplementation of monocalcium phosphate. Regressing daily digested P against daily P intake resulted in TTTD of 84.3% for P in monocalcium phosphate. In Exp. 2, ADG, ADFI, and G:F increased both linearly (P<0.01) and quadratically (P<0.05) with increasing P level in wk 1 and 3 and for the overall 3-wk duration. In wk 2, both linear and quadratic effects of P level were observed for ADG and ADFI (P<0.05) whereas the G:F only showed linear improvement (P<0.01). The true digestible P requirement, defined as the breakpoint using the overall 3-wk G:F as the response variable, was estimated to be 3.03, 2.98, and 3.08 g/kg of diet for pigs of mixed sex, barrows, and gilts, respectively. Using ADG, the corresponding estimates of P requirement were 3.09, 3.08, and 3.10 g/kg of diet. In conclusion, the mean true digestible P requirement of pigs from 20 to 40 kg BW was determined to be 3.06 g/kg of diet using the average of the estimates for barrows and gilts based on ADG.

This cross-sectional study investigates whether serum 25-hydroxyvitamin D3 [25(OH)D3] and intact parathyroid hormone (iPTH) are affected by vitamin D, calcium, or phosphate intake in 140 independently living elderly subjects from Germany (99 women and 41 men; age, 66-96 years). We hypothesized that habitual dietary intakes of vitamin D, calcium, and phosphate are not associated with 25(OH)D3 or iPTH and that body mass index confounds these associations. Serum 25(OH)D3 and iPTH were measured by an electrochemiluminescence immunoassay. Dietary intake was determined using a 3-day estimated dietary record. The median dietary intake levels of vitamin D, calcium, and phosphate were 3 μg/d, 999 mg/d, and 1250 mg/d, respectively. Multiple regression analyses confirmed that dietary vitamin D and calcium did not affect 25(OH)D3 or iPTH; however, supplemental intakes of vitamin D and calcium were associated with 25(OH)D3 after adjustment for age, sex, body composition, sun exposure, physical activity, and smoking. In addition, phosphate intake and the calcium-to-phosphate ratio were associated with iPTH after multiple adjustments. In a subgroup analysis, calcium and vitamin D supplements, as well as phosphate intake, were associated with 25(OH)D3 and/or iPTH in normal-weight subjects only. Our results indicate that habitual dietary vitamin D and calcium intakes have no independent effects on 25(OH)D3 or iPTH in elderly subjects without vitamin D deficiency, whereas phosphate intake and the calcium-to-phosphate ratio affect iPTH. However, vitamin D and calcium supplements may increase 25(OH)D3 and decrease iPTH, even during the summer, but the impact of supplements may depend on body mass index., (Copyright © 2013. Published by Elsevier Inc.)

Background: High fibroblast growth factor-23 (FGF-23) levels are associated with adverse outcomes. We studied the responsiveness of FGF-23 and mineral metabolism to altered dietary phosphate intake in chronic kidney disease (CKD) and healthy control patients., Methods: Thirty patients were enrolled: 18 normophosphatemic CKD subjects and 12 healthy controls. The study duration was 21 days with three 7-day dietary interventions; a high phosphate (HP, 2000 mg/day), low phosphate (750 mg/day) and low phosphate plus phosphate binder (aluminum hydroxide, 500 mg thrice daily with meals), with comparable macronutrient content, administered in random sequence. Baseline and weekly fasting morning measurements of FGF-23, serum phosphate (sPO(4)), 1,25-hydroxyvitamin D (1,25 D) and 24-h urinary calcium (uCa) and phosphate (uPO(4)) were collected., Results: FGF-23 levels were higher in subjects versus controls (72 pg/mL versus 30 pg/mL) at baseline, while sPO(4) remained in the normal range throughout the study. The absolute changes of uPO(4) and uCa for CKD and controls vary according to diet. The absolute changes of FGF-23 and sPO(4) suggest that the effect of the diets might also depend on the CKD status (P-values interaction effect = 0.08 and 0.07, respectively); nonetheless, these changes are evident as a function of dietary interventions, irrespective of CKD status (P-values diet effect = 0.006 and <0.001, respectively)., Conclusions: FGF-23 levels appear to be responsive to changes in diet in both CKD patients and controls. Further studies are required to determine whether lowering dietary phosphate and thus FGF-23 levels are of long-term benefit in CKD patients, irrespective of sPO(4) levels.

We studied the effects of dietary mineral source and oil intake on kidney calcification in 4-wk-old female Fischer rats after consuming the AIN-76 purified diet (AIN-76). A modified AIN-76 mineral mixture was used, although the original calcium (Ca)/phosphorus (P) molar ratio remained unchanged. Rats were fed the modified diets for a period of 40 d before their kidneys were removed on the last day. Ca balance tests were performed on days 31 to 36 and biochemical analysis of urine was also studied. Kidney Ca, P, and magnesium (Mg) in the standard diet group (20% protein and 5% oil) were not affected by the mineral source. Kidney Ca, P, and Mg in the low-protein (10% protein) diet group, were found to be influenced by the dietary oil content and mineral source. In particular, the different mineral sources differentially increased kidney mineral accumulation. Pathological examination of the kidney showed that the degree of kidney calcification was proportional to the dietary oil content in the 10% dietary protein group, reflecting the calcium content of the kidney. The information gathered on mineral sources in this study will help future researchers studying the influence of dietary Ca/P molar ratios, and histological changes in the kidney.