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PubMed1991

Effects of maleic acid on renal phosphorus transport: role of dietary phosphorus.

The effects of maleic acid on renal phosphate (Pi) transport were examined by clearance and brush-border membrane vesicle (BBMV) transport studies. In normal rats, maleic acid 50 mg.kg body wt-1.h-1 increased the phosphaturia (P less than 0.001). Intraperitoneal administration of a similar dose of maleic acid decreased the BBMV uptake of Pi but not glucose. In rats fed a low-phosphate diet (0.03%), the maleic acid-induced phosphaturia was blunted, but the inhibitory effect on the BBMV transport of Pi persisted. In chronic parathyroidectomized rats fed a low-phosphate diet, where the filtered load of Pi was higher than in the previous groups, the phosphaturia was abolished, but the inhibition of the BBMV transport of Pi was sustained. Both the in vitro incubation of BBMVV and in vivo administration of maleic acid were associated with a competitive inhibition of Pi transport. These studies indicate that the maleic acid-induced phosphaturia is expressed at the apical membrane entry step of Pi, and the enhanced distal tubular reabsorption accounts for the lack of phosphaturia in dietary Pi deprivation.

Animals↗
PubMed1992

Influence of postfast dietary crude protein and phosphorus content on nitrogen, phosphorus, calcium, and magnesium repletion in sheep.

An experiment was conducted to determine the influence of postfast dietary CP and P concentration on the repletion of N, P, Ca, and Mg lost during a 3-d fast in sheep. Four Suffolk wether lambs averaging 35 kg were used in a 4 x 4 Latin square design. Lambs were fed a control diet (700 g/d; as-fed basis) for 14 d and were then deprived of feed and water for 3 d. Lambs were then fed one of four isoenergetic realimentation diets: 1) low CP/low P, 2) low CP/high P, 3) high CP/high P, and 4) high CP/very high P. Realimentation N and Mg intakes were 9.8 and 1.1 g/d for lambs fed the low-CP diet and 18.1 and 1.7 g/d for lambs fed the high-CP diets, respectively. Realimentation P intakes were 1.40, 2.36, 2.66, and 3.82 g/d for lambs fed Diets 1, 2, 3, and 4, respectively. Nitrogen, P, Ca, and Mg apparent digestibility and balance and serum urea N, free fatty acids, P, Ca, Mg, and alkaline phosphatase were determined during the prefast, fast, and realimentation periods. Lambs fed the high-CP diets had higher (P less than .05) N and P digestibility and balance than lambs fed the low-CP diet. Increasing the dietary P content did not affect (P greater than .15) P balance or digestibility. In general, the realimentation diet fed did not affect (P greater than .15) serum concentrations of free fatty acids, alkaline phosphatase, inorganic P, Ca, or Mg.

Absorption↗
PubMed1996

Adverse effects of wide calcium:phosphorus ratios on supplemental phytase efficacy for weanling pigs fed two dietary phosphorus levels.

Ninety-six weanling pigs (initial BW = 9.3 kg, initial age = 37 d) were used in a 4-wk experiment to evaluate the response to three Ca: total (t) P ratios (1.2:1, 1.6:1, or 2.0:1) fed in combination with two P levels (.07 or .16% available that correspond to .36 or .45% tP) and two phytase levels (PY; 700 or 1,050 units/kg of diet). A 3 x 2 x 2 factorial arrangement of treatments was employed using a corn-soybean meal diet. Performance, serum mineral concentrations and alkaline phosphatase (ALP) activity, Ca and P digestibility and excretion, and bone mechanical measurements were examined. Average daily gain (P < .001), average daily feed intake (P < .01), and gain:feed (P < .05) were decreased linearly as the Ca:tP ratio became wider. The digestibility of P and Ca were decreased (P < .001) linearly as the Ca:tP ratio became wider. The digestibility of P (P < .001) and fecal P excretion (P < .01) were increased at the higher level of P. Increasing PY from 700 to 1,050 units (U)/kg of diet increased (P < .05) P digestibility and decreased (P < .01) P excretion but did not improve bone measurements. Shear force, stress and energy, and percentage of ash of both metacarpal and 10th rib linearly decreased (P < .001 to .05) as the Ca:tP ratio became wider, and bone measurements were generally greater for pigs fed the higher P level. Serum Ca concentration increased (P < .01) and the P concentration decreased (P < .001) as the Ca:tP ratio increased, but Mg, Zn, and ALP activity were not influenced by the Ca:tP ratio. Serum Ca and P concentrations were affected by PY supplementation over the 4-wk trial, but serum Mg and Zn concentrations were not affected by dietary treatments. Adverse effects of a wide Ca:tP ratio were greater at the low P diet for all responses. In addition, the activity of supplemental PY in diets seemed to be decreased as the Ca:tP ratio became wider and this negative effect of Ca:tP ratio seemed greater at the low P level, and seemed to parallel the effects of Ca:tP ratio on performance, P digestibility, bone, and serum measurements. Narrowing the dietary Ca:total P ratio from 2.0:1 to 1.2:1 led to an approximate 16% increase in phytase efficacy for improving performance, digestibility, bone measurements, and serum Ca levels.

6-Phytase↗
PubMed2000

Effects of dietary calcium:phosphorus ratios on apparent absorption of calcium and phosphorus in the small intestine, cecum, and colon of pigs.

Thirty-two crossbred barrows were used to investigate the effects of dietary Ca:total P (tP) ratios in phytase-supplemented diets on the apparent absorption of P and Ca in the small intestine, cecum, and colon. Three Ca:tP ratio treatments (1.5:1, 1.3:1, or 1.0:1) were created by adjusting the amount of ground limestone added to the basal low-P grower (.39% tP including .07% added inorganic P) and finisher (.32% tP without added inorganic P) diets. All low-P ratio diets were supplemented with Natuphos phytase at 500 units/kg. A positive control diet without phytase supplementation contained adequate P and Ca to meet dietary requirements. At 123 kg, the pigs were slaughtered and the contents of ileum, cecum, and colon were collected. Lowering the dietary Ca:tP ratio in the diets containing phytase linearly increased (P < .01) the apparent absorption (% and g/d) of P in the small intestine, but Ca absorption was not affected. Pigs fed the low-P diet with a Ca:tP ratio of 1.0:1 had an apparent absorption (g/d) of P or Ca similar to that of pigs fed the control diet, which was adequate in Ca and P. Averaged across all diets, the apparent absorption of P was highest when measured at the cecum, and the apparent absorption of Ca was highest when measured at the colon. In conclusion, lowering the dietary Ca:tP ratio to 1.0:1 in a low-P diet containing phytase increased the apparent absorption of P in the small intestine. Furthermore, a significant amount of P was absorbed in the cecum.

6-Phytase↗
PubMed2004

High dietary phytase levels maximize phytate-phosphorus utilization but do not affect protein utilization in chicks fed phosphorus- or amino acid-deficient diets.

Four trials investigated the effect of high levels of three phytase enzymes on P and protein utilization in chicks. The three phytases were derived from Aspergillus (Fungal Phytase 1), Peniophora (Fungal Phytase 2), and E. coli. Within each assay, 8-d-old male chicks were given ad libitum access to their experimental diet for 10 to 14 d. For Trials 1, 2, and 3, the basal diet was a corn-soybean meal diet deficient in P that was analyzed to contain 23% CP and 0.38% total P (0.10% estimated available P, as-fed basis). Phytase supplementation levels were based on the assessment of phytase premix activity (i.e., P release from Na phytate at pH 5.5 and 37 degrees C). In Trial 1, supplementation of inorganic P from KH2PO4 (0 to 0.20%) resulted in a quadratic (P < 0.05) response in weight gain, gain:feed, and tibia ash concentration but a linear (P < 0.01) increase in tibia ash weight. Tibia ash was higher (P < 0.01) for chicks fed E. coli phytase than for those fed Fungal Phytase 1 at 500, 1,000, and 5,000 phytase units (FTU)/kg, but did not differ between these two phytases at 10,000 FTU/kg. In Trial 2, E. coli phytase supplementation at 1,000 FTU/kg maximized growth and bone responses, whereas addition of either of the two fungal phytases resulted in increasing responses up to 5,000 and 10,000 FTU/kg. Dietary addition of Fungal Phytase 2 resulted in the poorest (P < 0.01) responses among the three phytases. Escherichia coli phytase supplementation at 10,000 FTU/kg in Trial 3 resulted in tibia ash (millligrams) responses that were greater (P < 0.05) than those resulting from either 0.35% inorganic P supplementation or 10,000 FTU/kg of Fungal Phytase 1 or 2. Trial 4 showed that E. coli phytase supplementation at either 500 or 10,000 FTU/ kg did not improve protein efficiency ratio (gain per unit of protein intake) of chicks fed low-protein soybean meal or corn gluten meal diets that were first-limiting in either methionine or lysine, respectively. These results demonstrate that high dietary levels of efficacious phytase enzymes can release most of the P from phytate, but they do not improve protein utilization.

6-Phytase↗
PubMed2006

Estimation of true phosphorus digestibility and endogenous phosphorus loss in growing pigs fed conventional and low-phytate soybean meals.

This study reevaluated the method of regressing of total P output against dietary P intake to simultaneously estimate true P digestibility and endogenous P loss in growing pigs fed either conventional or low-phytate soybean meal (SBM). Four isocaloric diets were formulated to contain increasing concentrations of each type of SBM (8 diets total), and therefore contained increasing concentrations of dietary P. Dietary P and Ca concentrations were deficient because they were supplied solely by SBM, and Ca:total P ratios were less than 1:1. Sixteen barrows (initial BW 17.7 +/- 1.8 kg) were surgically fitted with a simple T-cannula at the distal ileum, randomly assigned to metabolism crates, and fed the experimental diets in a replicated 8 x 8 Latin square design. Feed was provided at 90 g/kg of BW(0.75) and fed in 2 equally sized meals at 0800 and 2000, with diets containing Cr sesquioxide (3 g/kg) as an indigestible marker. As the P concentration increased from 0.9 to 3.9 g/kg of DM, the apparent prececal P digestibility increased for conventional SBM (P < 0.05), but no relationship was observed for low-phytate SBM. The output of total P [mg/(kg of BW(0.75).d)], either prececal or total tract, exhibited a linear relationship (P < 0.01) with increasing P intake. However, a quadratic response (P = 0.02) was also detected for total tract P output from pigs fed low-phytate SBM. True P digestibility was not different between prececal and total tract collection sites (P > 0.10), but was greater (P < 0.01) for low-phytate SBM (62.6%) compared with conventional SBM (44.5%). Endogenous P estimates were not different between the SBM varieties and averaged 4.83 mg/(kg of BW(0.75).d). However, endogenous P estimates were highly variable between individual animals and, therefore, were not significantly different from zero. In this study, estimates of endogenous P loss from pigs were relatively low compared with previously reported values, and evidence of nonlinearity in P output was observed. These results suggest that the difference in true P digestibility between conventional SBM and low-phytate SBM is influenced by dietary phytate content when growing pigs are fed P-deficient diets.

Animal Feed↗
PubMed2001

Nitrogen and phosphorus partitioning in lactating Holstein cows fed different sources of dietary protein and phosphorus.

To evaluate dietary N and P partitioning, 36 Holstein cows grouped by parity were assigned at calving to diets supplemented with soybean meal (S) or a combination of S and blood meal (B). Diets S and B were formulated to contain 16.2% CP and 0.35% P using mono- and dicalcium phosphate (PM) or wheat bran (WB) as the supplemental source of P. Actual dietary P contents were 0.38, 0.36, 0.34, and 0.34% for SPM, BPM, SWB, and BWB. Two-day total collections of feces, urine, and milk were conducted between 30 and 45 d in milk (DIM), then all cows were fed a control diet until 120 DIM. Between 120 and 150 DIM, cows were again fed the diet assigned at calving, then 2-d total collections of feces, urine, and milk were conducted. Milk production was similar for cows fed diets containing WB (SWB or BWB) when compared with cows fed PM. However, DMI tended to be lower, and P intake and total P excretion were lower in response to WB (20.7 kg/d, 71.9 g/d, and 40.3 g/d) compared with cows fed PM (23.0, 86.7, and 46.8 g/d). Apparent digestibility of dietary P did not differ due to source of supplemental P, averaging 45% across diets. The lower P intake by cows fed WB resulted in lower absorbed P and lower retained P (32.2 and 7.5 g/d) compared with those fed PM (40.6 and 13.4 g/d). Apparent N digestibility, urinary N, and N retention were not affected by P source. Blood meal decreased apparent N digestibility and absorbed N, and also decreased P retention compared with S. In later lactation, cows retained proportionately more absorbed N and P in body tissue and secreted less in milk than they did in early lactation. Results indicated the organic source of P (phytate-P) in WB can be used to provide a substantial portion of the P needed in dairy cattle diets after peak lactation, but the amount of WB in the diet during early lactation should be limited to prevent suppression of DMI and P retention.

Absorption↗
PubMed2001

Milk production, estimated phosphorus excretion, and bone characteristics of dairy cows fed different amounts of phosphorus for two or three years.

Diets containing 0.31, 0.39, or 0.47% P on a DM basis were fed to 10, 14, and 13 multiparous Holstein cows, respectively, for a full lactation. Most of the cows (33) were fed similar amounts of P in the previous one or two lactations. The objective was to obtain information on bone integrity after prolonged feeding of different amounts of P. At the end of the experiment, a section (-20 cm) of the 12th rib was surgically removed. The bone was tested for strength and analyzed for ash and P content. The shear strength and the energy required to deform the bone to the point of fracture did not differ among treatments. Bone specific gravities were 1.50, 1.57, and 1.55 for the three treatments. Ash and P content of the bone, measured in wet weight, dry weight, and wet bone volume, were similar for the 0.39 and 0.47% P treatments, but tended to be lower with the 0.31% P treatment. Milk production of cows in all groups was high, averaging >11,900 kg for the 308-d lactation. Feeding P at 0.31% of dietary DM over two to three lactations appeared to decrease P concentration of bone, but the decrease was not severe enough to affect bone strength. Dietary P at 0.39% did not affect bone P content or strength. Dietary P content of 0.31% appears to be borderline deficient for cows producing >11,900 kg/308 d.

Animals↗
PubMed1988

Influence of dietary calcium on phosphorus absorption and excretion and on phosphorus-33 distribution in laying hens.

An experiment was conducted using isotope-dilution and comparative balance techniques to estimate urinary and fecal P excretion of laying hens fed different levels of dietary Ca. Two levels of dietary Ca (3.46 and 4.2%) were fed to eight hens for 30 days. After 30 days, 50 microCi of the radioisotope 33P was injected intramuscularly to label endogenous P. On the 2nd day after 33P dosing and at 1 h postoviposition, plasma, liver, kidney, femur bone, whole egg, ileum, ileal digesta, and excreta samples were collected from each hen. Results showed a favorable effect of increasing dietary Ca consumption (2.91 vs 3.57 g/hen per day): femur ash increased (P less than .08), excreta P decreased (P less than .03), and urinary P decreased (P less than .06). The P content of ileal digesta was not affected by dietary Ca intake, but excreta P was greater for hens consuming less Ca, indicating that, during the collection period, excretion of P in urine was increased by the low Ca diet. Endogenous P secretions constituted less than 1% of the P in ileal digesta and excreta samples and this proportion was not changed by dietary Ca consumed.

Animals↗