Phosphorus Excretion Research Articles

Alkaline urine is associated with increased risk of calcium phosphate nephrolithiasis in medically complex children receiving enteral nutrition.

Calcium phosphate stones are commonly found in medically complex children (MCC) receiving enteral feeds. The objective of this study is to investigate the etiology for calcium phosphate stones in this patient population. This is a retrospective cohort study of gastrostomy fed, MCC who presented to a high-volume Pediatric Stone Center from 2015 to 2019. MCC were defined as those with a diagnosis of cerebral palsy and/or severe developmental delay who were non-ambulatory. A control group was composed of newly presenting patients to the stone clinic without comorbid conditions. Twenty-four hour urine collections were performed prior to medical intervention and were compared between MCC and controls. Twenty-four MCC children were compared to 38 controls. The median age (interquartile range [IQR]) and weight of MCC were 11.9 (7.5, 16.3) years and 28.6 (21.0, 37.0) kg. Urine supersaturation of calcium phosphate (SSCaP) was similar in MCC and controls (1.7 and 2.0, p=0.40). Weight-based 24-h urine calcium and phosphorus excretion were also similar in MCC and controls. The median BSA-adjusted urine volume was significantly higher in MCC vs controls (2.2 vs. 1.2L/1.73m2, p<0.001), which contributed to lower 24-h average urinary phosphorus (271.9 vs. 689.7mg/L, p<0.001) and calcium concentrations (73.3 vs. 132.8mg/L, p<0.001). However, urine pH was significantly higher in MCC (7.4 vs. 6.3, p<0.001), as was net gastrointestinal absorption of alkali (1.1 vs. 0.3 mEq/kg/day, p<0.001). In regression analysis, SSCaP increased by a factor of 2.82 for every 1-unit increase in urine pH (p<0.001). A high urine pH is associated with an increased risk of calcium phosphate nephrolithiasis in MCC. This may be caused by a higher alkaline content of enteral feeding formulations compared to children on a standard American diet.

Safety and Phosphate-Binding Capacity of Oxylanthanum Carbonate in Healthy Volunteers.

Despite the widespread use of currently available serum phosphate management options, elevated serum phosphate is common in patients with end-stage kidney disease on dialysis. Characteristics of currently available phosphate binders that lead to poor patient experiences such as large drug volume size of required daily medication (e.g., many large tablets) and adverse gastrointestinal effects may decrease compliance to labeled dosing instructions, thus decreasing their efficacy. Oxylanthanum carbonate is a new molecule yielding the same phosphate-binding capacity as lanthanum carbonate, but in a much smaller drug volume and tablet size. It is formulated as small tablets that can be easily swallowed. In a double-blind dose-escalation phase 1 study, healthy volunteers (n = 32) were randomly divided into four treatment arms and randomly assigned to receive oxylanthanum carbonate tablets or a placebo over a period of 4 days to evaluate safety, urinary and fecal excretion of phosphorus, and pharmacokinetics. Each treatment arm evaluated a different dose of oxylanthanum carbonate: 500, 1000, 1500, or 2000 mg three times a day (TID). The study drug was well-tolerated. Oxylanthanum carbonate effectively decreased dietary phosphorus absorption, demonstrated by decreased urinary phosphorus excretion and increased fecal phosphorus excretion. Systemic absorption of oxylanthanum carbonate was minimal, with lanthanum serum concentration values below the level of quantification (0.500 ng/mL) in all subjects receiving 500 mg TID and did not exceed 0.7 ng/mL at other doses. Future studies should evaluate and confirm the ability of oxylanthanum carbonate to reduce pill burden and improve dose administration, patient tolerability, adherence, and treatment outcomes. Trial Registration: ClinicalTrials.gov identifier: NCT01560884.

Prediction models for phosphorus excretion of pigs.

The present study aimed to measure fecal and urinary phosphorus (P) excretion from pigs and to develop prediction models for P excretion of pigs. A total of 96 values for P excretions were obtained from pigs of 15 to 93 kg body weight (BW) fed 12 diets in four experiments and were used to develop the prediction models. All experimental diets contained exogenous phytase at 500 phytase units per kg. Body weight of pigs and dietary P concentrations were used as independent variables in the prediction models. The BW, feed intake, and P intake were positively correlated with total (fecal plus urinary) P excretions (r = 0.80, 0.91, and 0.94, respectively; p<0.001). The models for estimating P excretion were: fecal P excretion (g/d) = -0.654-0.000618×BW2+0.273×BW ×dietary P concentration (R2 = 0.83; p<0.001); urinary P excretion (g/d) = 0.045+ 0.00781×BW×dietary P concentration (R2 = 0.15; p<0.001); total P excretion (g/d) = -0.598-0.000613×BW2+0.280×BW×dietary P concentration (R2 = 0.86; p<0.001) where the BW of pigs and dietary P concentration are expressed as kg and % (as-fed basis), respectively. Based on the developed prediction models, the estimated annual fecal, urinary, and total P excretion for a market pig was 1.24, 0.09, and 1.33 kg/yr, respectively. The P excretions in market pigs can be estimated using BW of pigs and dietary P concentration. In the present model, a market pig excretes 1.24 kg of fecal P and 0.09 kg of urinary P per year.

Physiological changes in the regulation of calcium and phosphorus utilization that occur after the onset of egg production in commercial laying hens.

At the onset of egg production, physiological changes governing calcium and phosphorus utilization must occur to meet demands for medullary bone formation and eggshell mineralization. The objective of this study was to identify these changes and determine if they are influenced by dietary supplementation with 1α-hydroxycholecalciferol (AlphaD3™, Iluma Alliance). Commercial laying hens fed either a control or AlphaD3-supplemented diet beginning at 18 weeks of age were sampled at 18 (n = 8) and 31 weeks (n = 8/diet) to evaluate mRNA expression associated with calcium and phosphorus utilization in kidney, shell gland, ileum, and liver, circulating vitamin D3 metabolites, and bone quality parameters in humerus, tibia, and keel bone. Though diet did not heavily influence gene expression at 31 weeks, several significant differences were observed between 18- and 31-week-old hens. Heightened sensitivity to hormones regulating calcium and phosphorus homeostasis was observed at 31 weeks, indicated by increased parathyroid hormone receptor 1, calcium-sensing receptor, calcitonin receptor, and fibroblast growth factor 23 receptors in several tissues. Increased renal expression of 25-hydroxylase and vitamin D binding protein ( DBP ) at 31 weeks suggests kidney participates in local vitamin D3 25-hydroxylation and DBP synthesis after egg production begins. Biologically active 1,25(OH)2D3 was higher at 31 weeks, with correspondingly lower inactive 24,25(OH)2D3. Increased expression of plasma membrane calcium ATPase 1 and calbindin in kidney, shell gland, and ileum suggests these are key facilitators of calcium uptake. Elevated renal inorganic phosphorus transporter 1 and 2 and sodium-dependent phosphate transporter IIa at 31 weeks suggests increased phosphorus excretion following hyperphosphatemia due to bone breakdown for eggshell formation. Diet did influence bone quality parameters. Bone mineral density in both humerus and tibia was higher in AlphaD3-supplemented hens at 31 weeks. Tibial bone mineral content increased between 18 and 31 weeks, with AlphaD3-supplemented hens increasing more than control hens. Moreover, control hens exhibited diminished tibial breaking strength at 31 weeks compared to hens at 18 weeks, while AlphaD3-supplemented hens did not. Together, these results indicate supplementation with AlphaD3 enhanced bone mineralization during the medullary bone formation period and elucidate the adaptive pathways regulating calcium and phosphorus utilization after the onset of lay.

Urinary Response to Consuming Plant-Based Meat Alternatives in Persons with Normal Kidney Function: The SWAP-MEAT Pilot Trial.

Consuming excess animal meat may exacerbate kidney disorders, such as urinary stone disease and CKD. Plant-based meat alternatives imitate animal meat and replace animal with vegetable protein, but it is unclear whether eating plant-meat confers similar health benefits as eating whole vegetables. We hypothesized that eating plant-meat when compared with animal meat decreases dietary acid load but increases dietary phosphorus and nitrogen. The Study With Appetizing Plantfood—Meat Eating Alternatives Trial was a randomized 8-week, crossover trial (NCT03718988) of participants consuming ≥2 servings/d of either plant-meat or animal meat for each 8-week phase. We measured urine sulfate, ammonium, pH, phosphorus, urea nitrogen (UUN), citrate, and creatinine concentrations and serum creatinine and bicarbonate concentrations from stored participant samples from each phase. At a single site, we enrolled 36 generally healthy participants (mean±SD age 50.2±13.8 years, 67% women, and 69% White). Eating the plant-meat diet versus eating the animal meat diet was associated with lower mean concentration of urine sulfate (−6.7 mEq/L; 95% confidence interval [CI], −11.0 to −2.4), urine ammonium (−4.2 mmol/L; 95% CI, −8.2 to −0.1), urine phosphorus (−9.0 mg/dl; 95% CI, −17.5 to −0.5), and UUN (−124.8 mg/dl; 95% CI, −226.9 to −22.6). Eating plant-meat compared with eating animal meat was associated with higher mean urine pH (+0.3 units; 95% CI, 0.2 to 0.5) and mean urine citrate/creatinine ratio (+111.65; 95% CI, 52.69 to 170.60). After participants consumed a plant-meat diet compared with when they consumed an animal meat diet, mean serum creatinine concentration was lower (−0.07 mg/dl, 95% CI, −0.10 to −0.04), whereas mean serum bicarbonate concentration was not different. Eating plant-based meat products, compared with eating animal meat, was associated with lower urinary excretion of sulfate, ammonium, phosphorus, and UUN and higher urinary excretion of citrate. Our findings provide rationale for examining whether plant-based meat will benefit patients with kidney disease.

Precision feeding as a tool to reduce the environmental footprint of pig production systems: a life-cycle assessment.

Nitrogen and phosphorus excretion are major sources of environmental contamination in growing-finishing pig operations. Nutrient excretion can be reduced by feeding pigs daily-tailored diets to their estimated nutrient requirements using individual precision feeding (IPF) techniques. This study modeled and evaluated the environmental impact of moving from conventional group 3-phase feeding (CGF) to IPF systems in Quebec, Canada, using life-cycle assessment with SimaPro software. The cradle-to-farm model included inputs and outputs of each subphase: raw materials/feedstuffs production, feed mill processing, transport, animal rearing, and manure management. The model was identical for both treatments in all aspects except for the production of feeds and barn and manure emissions in the growing-finishing phases. All feed ingredients originated from Quebec, simulating agricultural practices using real management data from an average farm in Quebec. Based on observed pig growth data, the CGF and IPF systems were compared in the growing-finishing phase. IPF diets were modeled as the blend of 2 feeds (i.e., A and B), while CGF diets were stablished according to the industry. The evaluated impact categories were global warming potential (GWP), eutrophication potential (EP), and acidification potential (AP). The functional unit was 1 t of feed at the feed mill gate and 1 t of finished pig live weight at the farm gate. A Monte Carlo analysis determined the uncertainty of the growth performance results. Feeding programs were compared using analysis of variance. Corn was associated with elevated GWP and AP impacts, leading to higher impacts for diets with higher corn content. Feed B, which contained 83% corn, resulted in impacts of 645kg of CO2-eq., 8.53kg SO2-eq., and 4.89kg PO4-eq. Diets with higher EP impact had a higher percentage of soybean meal. Feed A contained 25% of this ingredient and had an impact of 608kg CO2-eq., 6.98kg SO2-eq., and 5.57kg PO4-eq. CGF diets had environmental impacts between those of feeds A and B. Compared to CGF, applying IPF programs during the growing-finishing phase decreased GWP by 7.6%, AP by 16.2% and EP by 13.0%. IPF significantly reduced the environmental impact in all categories through the more efficient use of nutritional resources by pigs. IPF could help to improve the sustainability of growing-finishing pig operations in Quebec and likely other regions using corn and soybean-based diets.

Glucocorticoid-induced acute diuresis in rats in relation to the reduced renal expression of sodium-dependent cotransporter genes

Although several studies have shown that glucocorticoids exert diuretic effects in animals and humans, the underlying mechanism responsible for the acute diuretic effect remains obscure. Here we examined the mechanism in terms of gene-expression. We observed that glucocorticoids, including dexamethasone (Dex) and prednisolone (PSL), acutely induced diuresis in rats in a dose-dependent manner. Free water clearance values were negative after Dex or PSL treatment, similar to those observed after treatment with osmotic diuretics (furosemide and acetazolamide). Dex significantly increased the urinary excretion of sodium, potassium, chloride, glucose, and inorganic phosphorus. Renal microarray analysis revealed that Dex significantly altered the renal expression of genes related to transmembrane transport activity. The mRNA levels of sodium/phosphate (NaPi-2a/Slc34a1, NaPi-2b/Slc34a2, and NaPi-2c/Slc34a3) and sodium/glucose cotransporters (Sglt2/Slc5a2) were significantly reduced in the Dex-treated kidney, being negatively correlated with the urinary excretion of their corresponding solutes. Dex did not affect renal expression of the natriuretic peptide receptor 1 (Npr1) gene, or the expression, localization, and phosphorylation of aquaporin-2 (AQP2), a water channel protein. These findings suggest that the acute diuretic effects of glucocorticoids might be mediated by reduced expression of sodium-dependent cotransporter genes.

Dietary Fiber Fermentability and Viscosity Impact Phosphorus Homeostasis and Urinary Phosphorus Excretion in a Rat Model of Chronic Kidney Disease

Dietary Fiber Fermentability and Viscosity Impact Phosphorus Homeostasis and Urinary Phosphorus Excretion in a Rat Model of Chronic Kidney Disease

Health-Related Quality of Life during 26-Week Intervention with the New Nordic Renal Diet.

The New Nordic Renal Diet (NNRD) is a whole-food approach, tailored to meet recommended guidelines in patients with moderate chronic kidney disease (stage 3b-4). The NNRD improved various metabolic and physiological endpoints during a 26-week randomized controlled study. Here, we examined the effect of dietary intervention on health-related quality of life (HRQoL). Sixty participants were recruited (NNRD group n = 30, control group n = 30) and 58 completed the study. During the intervention, the NNRD group received food boxes, and recipes once a week. The control group continued their habitual diet. HRQoL was examined at baseline and at the end of the intervention using the validated EuroQol-5D-5L, including a 5-point scale Likert questionnaire at the end of the intervention. Assessed by the EuroQol-5D-5L questionnaire, the NNRD group experienced a reduction in pain/discomfort during the intervention by 26% [-0.44 points (95% CI; -0.73, -0.16)], compared with no change in the control group [0.25 points (95% CI; -0.02, 0.53)] and a between-group difference of -0.70 points (95% CI; -1.03, -0.37, p < 0.001). A larger decrease of body fat mass was associated with a larger decrease in pain/discomfort (p = 0.014). In addition, the NNRD group reported an overall improvement in conducting usual daily activities by 23% [-0.30-point (95% CI; -0.50, -0.11)], while no change was seen in the control group [-0.02 points (95% CI; -0.21, 0.17)], with a between-group difference -0.28 points (95% CI; -0.51, -0.06, p = 0.014). A larger decrease in 24 h urine phosphorus excretion, used as a marker of compliance, was associated with a larger improvement in conducting usual daily activities (p = 0.036). The NNRD group had a clinically relevant improvement in various HRQoL outcomes.

#1496 High levels of sclerostin promote bone resorption and changes and mineral metabolism

Abstract Background and Aims The physiological function of sclerostin (SOST) remains unknown. It is known that SOST is produced in osteocytes and functions as an inhibitor of the Wnt/β-catenin pathway. Similarly, it is well-established that low levels of SOST lead to bone alterations affecting cortical bone, resulting in osteopetrosis and reduced calciuria. High levels of SOST are associated with osteoporosis. In this study, we aimed to investigate the impact of three elevated doses of SOST on cortical, trabecular, and subchondral bone, as well as its relationship with other parameters of mineral metabolism. Method Bone histomorphometry, mCT, immunohistochemistry, and analysis of mineral metabolism parameters revealed that high doses of SOST over a 14-day period led to a reduction in trabecular bone volume due to a significant increase in bone resorption through the direct activation of osteoclastogenesis. Results Bone resorption, as measured by TRAP activity, was higher in trabecular, cortical, and subchondral bone. Similarly, high doses of SOST increased the number of hypertrophic chondrocytes, consequently expanding the growth plate area. Cortically, positive TRAP staining was observed, suggesting osteocytic osteolysis and trabecularization of cortical bone. The increased bone resorption resulted in a substantial rise in urinary excretion of phosphorus and calcium, accompanied by elevated levels of FGF23 and a significant decrease in PTH. Conclusion The findings suggest that elevated levels of SOST promote bone resorption through the activation of osteoclasts and the generation of osteocytic osteolysis. The increase in calcium and phosphorus levels led to changes in mineral metabolism, indicating a close relationship between SOST and other mineral metabolism parameters.

#1610 FGF23-mediated hypertension via augmented calcium entry in vascular smooth muscle cells

Abstract Background and Objectives Ongoing studies are shedding light on the potential connection between FGF23 and hypertension. In experimental settings, the administration of recombinant FGF23 in mice has been demonstrated to induce hypertension by elevating serum sodium, along with an increase in NCC receptors in the kidney. Clinical evidences further supports pro-hypertensive effects of high circulating levels of FGF23. Our group has previously demonstrated a direct influence of FGF23 on increased arterial stiffness by inducing a phenotypic transition in vascular smooth muscle cells (VSMCs) from a contractile to a synthetic phenotype. This study aimed comprehensively to evaluate, both in vivo and in vitro, whether FGF23 directly leads to hypertension through the stimulation of intracellular calcium entry in vascular cells. Methods To ascertain whether FGF23 contributes to hypertension through a direct impact on blood vessels, recombinant FGF23 (15 µg/day) was administered for 28 days via Alzet pumps. Blood pressure was meticulously measured in these animals, and we investigated alterations in vascular remodeling and calcium channels, as well as proteins associated with vascular contraction such as Orai1, STIM1, PKD1, SERCA2a, and AGTR1. In vitro experiments included the evaluation of the effect of elevated levels of recombinant FGF23 (2 ng/ml) over 9 days on intracellular calcium entry stimulated by Ang2 (100 nM) or Thapsigargin (2.5 µM). We used the FURA method to conduct these experiments. To elucidate the in vitro pro-hypertensive mechanisms of FGF23, studies were conducted with the administration of inhibitors targeting FGF Receptors 1-3 (AZD4547, 150 nM), FGF Receptor-4 (BLU9931, 10 nM), and Erk1/2 phosphorylation (PD98059, 10 μM). Additionally, changes in Orai1, STIM1, PKD1, SERCA2a, and AGTR1 were also evaluated in these VSMCs. Results After 28 days of recombinant FGF23 treatment, no significant differences were observed in serum sodium levels, yet there was a marked increase in urinary phosphorus excretion. Systolic and diastolic blood pressure values showed a progressive significant elevation in animals exposed to high levels of FGF23. The expression of AGTR1 and PKD1 levels significantly increased after FGF23 administration for 28 days (Figure). However, Orai1 and STIM1 in the thoracic aorta exhibited no significant differences following FGF23 treatment. In VSMCs, the exposure to recombinant FGF23 for 9 days resulted in increased calcium entry upon Ang2 stimulation (Figure). This effect was markedly diminished after inhibiting FGFR1-3 receptors and Erk1/2 phosphorylation (Figure). Notably, the inhibition of FGF23 receptor 4 (FGFR4) had no impact on the calcium entry induced by FGF23 (Figure). While Orai1, STIM1, IP3R, and TRPV5 in VSMCs remained unaffected by recombinant FGF23 administration, PKD1, SERCA2, and AGTR1 levels were significantly elevated compared to control cells (Figure). The addition of Thapsigargin in a Ca2+-free culture medium to VSMCs incubated with recombinant FGF23 for 9 days led to increased Ca2+ efflux from endoplasmic reticulum. Conclusion Elevated levels of FGF23 directly enhanced calcium entry in VSMCs. This effect is mediated by FGFR1-3 receptors, Erk1/2 phosphorylation, and the upregulation of related protein to cell contraction such as SERCA2a, PKD1 or AGTR1. These modifications could be responsible of FGF23-associated hypertension in the experimental model.

Estimation of annual phosphorus excretion from pigs in Korea

Estimation of annual phosphorus excretion from pigs in Korea

Reference values of parathyroid hormone in very low birth weight infants.

The primary goal was to estimate reference values of parathyroid hormone (PTH) in very low birth weight infants without severe neonatal morbidity. A secondary objective was to assess the relationship between PTH serum levels and selected laboratory markers of bone metabolism. Ninety two infants with birth weight less than 1500g met the inclusion criteria of the study. Serum levels of PTH, 25-hydroxyvitamin-D [25(OH)D], C3-epi-25(OH)D, total calcium, phosphorus, and alkaline phosphatase, and urinary levels of calcium, phosphorus, and creatinine were examined on day 14 and subsequently every 2weeks until discharge. Of the total 167 serum samples examined for PTH levels in infants without 25(OH)D deficiency the estimated range was 0.9-11.9 pmol/l (8.5-112.3 pg/mL). During the first month, no statistically significant correlation was observed between PTH level and that of 25(OH)D, C3-epimers of 25(OH)D, S-Ca, S-P, or ALP, nor with urinary excretion of calcium and phosphorus. From the second month of life, there was a moderately significant correlation between PTH and 25(OH)D (Rho = -0.40, P =< .001), between PTH and calcium/creatinine ratio (Rho = -0.56, P = < .001), and between PTH and phosphorus/creatinine ratio (Rho = 0.51, P = < .001). The physiological range for PTH levels for preterm neonates without 25(OH)D deficiency was estimated as 0.9-11.9 pmol/l (8.5-112.3 pg/mL). It seems that elevation of serum PTH above this range can be considered as hyperparathyroidism in very low birth weight infants.

Post-intervention Adherence to the New Nordic Renal Diet among patients with chronic kidney disease, stages 3 and 4.

The New Nordic Renal Diet (NNRD) is a meal pattern reduced in phosphorus, protein, and sodium for patients with moderate chronic kidney disease. The NNRD showed improvements in metabolic, and physiological outcomes after 26-weeks intervention. In the original study, participants were randomized to NNRD (n = 30), or control (habitual diet) (n = 30). The aim of this study was to explore adherence to the NNRD 3 months after cessation of intervention (follow-up). Fifty-seven participants completed the follow-up visit, which consisted of fasting blood samples and 24 h urine samples. At follow-up, there was no longer a significant reduction in 24 h urine phosphorus excretion in the NNRD group. From intervention to follow-up, 24 h urine phosphorus increased by 63 mg in the NNRD group, vs. -24.1 mg in the control group, between-group difference 87.1 mg (-10.1, 184.3, p = 0.08). Our findings show that more active intervention is needed to support adherence and maintain beneficial effects of the NNRD.

Correlation of Calcium Metabolic Axis with Urinary Stone Characteristics

Background: Urinary stone disease (USD) refers to the presence of stones or salt crystals within the urinary tract, with calcium stones accounting for approximately 80% of cases. Increased urinary calcium and phosphorus excretion predispose individuals to urinary stones, with hypercalciuria being the most significant risk factor. Vitamin D plays a pivotal role in modifying urine calcium and phosphorus excretion, and it enhances calcium and phosphorus reabsorption in the kidneys. Urinary stone disease is a recognized risk factor for chronic kidney disease (CKD) and may also lead to life-threatening complications such as perinephric abscesses, urosepsis, and urinary tract malignancies. The role of serum vitamin D and its effects on serum calcium and phosphorus in urinary stone formation have been subjects of controversy. Objectives: This study aims to evaluate the associations between serum calcium, phosphorus, and vitamin D levels and urinary stones. Methods: This retrospective study involved two groups of 90 patients, one with urinary stones and the other without. Demographic and biochemical data, including serum calcium, phosphorus, and 25-(OH) vitamin D levels, were recorded for all patients. Patients were categorized into four groups based on their serum vitamin D levels: Excess, sufficient, insufficient, and deficient. The presence and characteristics of urinary stones were assessed using non-contrast CT scans. Results: The mean age of the patients was 54.62 ± 15.46 years. Laboratory investigations revealed mean serum calcium, phosphorus, and vitamin D levels of 9.56 ± 0.65 mg/dL, 3.53 ± 0.79 mg/dL, and 25.05 ± 12.96 ng/mL, respectively. This study demonstrated a significant correlation between serum calcium levels and the maximum diameter of urinary stones (correlation = 0.313, P-value = 0.005). No other significant associations were found between serum calcium, serum phosphorus, and serum vitamin D levels and the number of kidney stones, stone laterality, and type of kidney stone. There was also no significant difference between the two groups. Conclusions: In conclusion, the role of serum calcium, phosphorus, and 25-(OH) vitamin D levels in urinary stone formation remains controversial. This study suggests that there is no significant association between serum calcium, phosphorus, or 25-(OH) vitamin D and urinary stones, except for a positive association between serum calcium and the diameter of the stone.

Caracterização e digestão anaeróbia dos dejetos de suínos submetidos a restrição alimentar ou suplementados com ractopamina ou cromo

Abstract The aim of this study was to characterize the production and anaerobic digestion of manure from finishing pigs subjected to feed restriction or supplemented with ractopamine or chromium (Cr). The waste came from 50 barrows in the finishing phase, aged ± 154 days, with a starting weight of 99.0 ± 4.4 kg and a final weight of 117.2 ± 5.8 kg. The experimental diets were as follows: control (conventional diet), qualitative restriction (7.5% reduction in net energy compared to the control diet), quantitative restriction (15% reduction in feed supply), Cr (0.8 mg), and ractopamine (10 ppm). The data were subjected to an analysis of variance using a randomized block design, in which the weeks of analysis were considered blocks (cofactors). There were no differences in manure production between the diets regarding natural matter (NM), dry matter (DM), mineral matter (MM), or organic matter (OM). Animals fed the control diet had the highest residue coefficient, and there was no difference among the other diets. No differences were observed among the diets regarding total solids, pH, or total nitrogen in the tributaries or effluents. The highest biogas yield (574 mL g-1) of added volatile solids (VS) was obtained in the digesters supplied with manure from animals fed a qualitatively restricted diet. It can be concluded that a qualitatively restricted diet results in higher manure production but with lower nitrogen and phosphorus excretion and higher biogas yields.

Phosphorus-independent role of FGF23 in erythropoiesis and iron homeostasis.

A number of studies have reported an association between phosphorus, red blood cell (RBC) production, and iron metabolism. However, it is difficult to distinguish whether the effect of phosphorus is direct or through the actions of FGF23, and it is not clear whether phosphorus is positively or negatively associated with RBC production. In the present study, we investigated the effects of a) increased phosphorus load and b) phosphorus deficiency on erythropoiesis and iron metabolism in association with FGF23. Mice were fed either a 1.2% or 1.65% phosphorus diet and compared to mice fed a control diet containing 0.6% of phosphorus. Moreover, we used two mouse models of hypophosphatemia-induced either by dietary intervention in the form of a low phosphorus (LP) diet (0.02% of Pi) or genetically in a mouse model of X-linked hypophosphatemia (XLH)-that had opposite FGF23 levels. Phosphorus supplementation appropriately increased FGF23 levels leading to excretion of excess phosphorus and normalization of serum phosphorus levels. We also found that a phosphorus-rich diet results in inflammation-induced hypoferremia associated with reduced iron export leading to tissue iron overload. Moreover, high phosphorus intake results in ineffective erythropoiesis caused by decreased production (decreased RBCs, hemoglobin, hematocrit, and erythroid progenitors in the bone marrow) and increased destruction of RBCs, leading to anemia despite increased EPO secretion. These complications occur through the actions of elevated FGF23 in the presence of normophosphatemia. Our data also show that LP diet induces a decrease in the serum concentrations of phosphorus and FGF23, resulting in increased RBC counts, hemoglobin concentration, and hematocrit compared to mice fed normal diet. Moreover, serum iron and transferrin saturation were increased and positively correlated with serum ferritin, liver ferritin protein and mRNA expression in mice fed LP diet. However, hyp mice, the murine model of XLH, exhibit hypophosphatemia and high serum FGF23 levels, along with low number of circulating RBCs, hemoglobin, and hematocrit compared to wild-type mice. In the bone marrow, hyp mice showed reduced number of erythroid progenitors and formed significantly less BFU-E colonies compared to control mice. Serum iron levels and transferrin saturation were also decreased in hyp mice in comparison to control mice. Taken together, our data show that FGF23 acts independent of phosphorus levels to regulate erythropoiesis and iron homeostasis.

Gastrointestinal Parasite Infections and Environmental Sustainability of the Ovine Sector: Eimeria spp. Infections and Nitrogen and Phosphorus Excretions in Dairy Sheep in Italy.

In sheep farming, gastrointestinal parasites can be responsible for significant reductions in animal health and production. Nitrogen (N) and phosphorus (P) fecal excretions are the main determining factors for N2O emissions from manure management and may pose other environmental problems, such as the acidification and eutrophication of natural habitats. By using the Mini-FLOTAC technique on fecal samples from sheep of different ages and physiological status from 19 dairy sheep farms in Tuscany (central Italy), gastrointestinal parasite infections were evaluated. The animal N and P fecal contents were also assessed, with the aim of evaluating possible relationships between the identified parasites and the environmental sustainability of the examined farms. The obtained results showed that Eimeria spp. (86.36%) and gastrointestinal strongyle (54.55%) infections are prevalent in the examined farms. Moreover, significantly higher (p ≤ 0.05) P and Eimeria oocyst/gram-of-feces (OPG) values were found in fecal samples from animals < 1 year of age, and a significant (p ≤ 0.05) positive correlation resulted between N content and Eimeria OPG in fecal samples from animals in the first month of lactation. The findings from this study suggest for the first time that Eimeria spp. infections may have an impact on the environmental sustainability of sheep farming.

Teaching Nutrient Cycling and Climate Change Concepts Using Excretion Experiments with Common Fish

Many high school students learn about nutrient cycling during biology, environmental science, and agriculture classes. These lessons often focus on soil and plants, and nutrient cycling is usually taught independently from climate change. Scientists know that animals, including fish, can have strong effects on nutrient cycling (i.e., nitrogen and phosphorus) in ecosystems. Additionally, research has shown that nitrogen and phosphorus excretion rates of animals increase with water temperatures. We worked with high school students to design and conduct nutrient excretion experiments using common fish (zebrafish) to explore the impact of climate change on nutrient cycling. This allowed students to have hands-on laboratory experience. In 2021, we worked with students participating in a residential summer program in Georgia. Meanwhile, in 2022, students enrolled in the local high school visited the university campus on two occasions to participate in the experiments, and we once again worked with students in Georgia. Students from all three groups showed an increased understanding of the role of animals in nutrient cycling and ways climate change may impact these processes, despite variable results from the excretion experiments. Students also showed increased understanding of science processes and were more likely to feel like part of the science community. We believe that these experiments can be done in high school classrooms to expand students’ understanding of the scientific process, nutrient cycling, and climate change.

PSXI-17 Prediction Models for Phosphorus Excretion of Pigs

Abstract The objective of the present study was to develop prediction equations for daily phosphorus excretion based on body weight (BW) and dietary phosphorus concentration of pigs. Four experiments were conducted using pigs with an initial body weight of 15 kg, 30 kg, 50 kg, and 78 kg. In the experiment 1, the experimental diets were mainly based on corn, soybean meal, whey powder, fish meal, and blood plasma. In the experiments 2, 3, and 4, the diets based on corn, soybean meal, and fibrous ingredients were formulated. All experimental diets were supplemented with commercial phytase at 500 FTU/kg. In all experiments, a total collection method and the marker-to-marker procedure were used for fecal and urinary collection. Fecal and urinary phosphorus excretions were determined. Correlation coefficients among BW, daily phosphorus intake, and daily phosphorus excretion of pigs were determined. Prediction equations for phosphorus excretion were developed using BW and dietary phosphorus concentration as independent variables. The BW had positive correlations with fecal and total phosphorus excretion (r = 0.78 and P &amp;lt; 0.001 for fecal phosphorus excretion and r = 0.78 and P &amp;lt; 0.001 for total phosphorus excretion). The prediction equations for predicting fecal phosphorus excretion and total phosphorus excretion were: fecal phosphorus excretion (g·pig–1·d–1) = –0.647 – 0.00065 × BW2 + 0.270 × BW × dietary phosphorus concentration (R2 = 0.81; P &amp;lt; 0.001); total phosphorus excretion (g·pig–1·d–1) = –0.619 – 0.00064 × BW2 + 0.277 × BW × dietary phosphorus concentration (R2 = 0.85; P &amp;lt; 0.001) where BW in kg and phosphorus concentration in %. The BW of pigs corresponding to the age was predicted using the NRC model. The mean phosphorus excretion of pigs weighing from 7 kg to 120 kg at day 22 to 180 was calculated using a developed estimation equation, with BW and total phosphorus requirement used as independent variables. Daily fecal and total phosphorus excretions were 3.77 g·pig–1·d–1 and 4.01 g·pig–1·d–1, respectively.