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At least 19 recordsLinked to original sources
PubMed1984

The effect of variation in phosphorus intake on net intestinal phosphorus absorption, salivary phosphorus secretion and pathway of excretion in sheep fed roughage diets.

Mature sheep fitted with rumen and duodenal cannulae and fed either pelleted hay or grass diets were given supplements of Na2HPO4 by continuous infusion into the rumen and the effects on salivary phosphorus secretion, intestinal phosphorus absorption and pathway of excretion were studied. Little phosphorus was excreted in the urine in control periods and little increase was seen in response to phosphorus supplementation, most of the extra phosphorus given being recovered in the faeces. Infusion of phosphorus into the rumen led to an increase in the flow of phosphorus to the intestine, an increase in absorption, a rise in plasma phosphate level and an increase in salivary phosphorus secretion while withdrawal of supplementary phosphorus was seen to have the opposite effects. In separate studies short sections of the upper small intestine temporarily isolated from the normal flow of digesta were perfused with solutions containing NaH2PO4 (5-50 mmol.l-1). Phosphorus absorption increased with increasing concentration though the relationship was curvilinear such that absorptive efficiency fell from around 0.7 at 5 mmol.l-1 to around 0.35 at a concentration of 50 mmol.l-1. The significance of these results in relation to the control of phosphorus balance in ruminants is discussed.

Absorption↗
PubMed1985

The effects of feeding either roughage or concentrate diets on salivary phosphorus secretion, net intestinal phosphorus absorption and urinary phosphorus excretion in the sheep.

Mature sheep fitted with rumen and duodenal cannulae were fed either a hay or a concentrate diet and the effects on salivary phosphorus secretion, net intestinal phosphorous absorption and pathway for phosphorous excretion were examined. Route of excretion was markedly affected by diet with urine phosphorus levels being much higher and faecal levels lower when the concentrate diet was fed. This difference was not due to differences in phosphorus intake nor could it be related to differences in either plasma phosphorus levels or net intestinal phosphorus absorption. Salivary phosphorus secretion and renal tubular reabsorptive efficiency for phosphorus were, however, both lower when the concentrate diet was fed. The significance of these effects of diet in relation to the control of phosphorus balance in ruminants is discussed.

Animal Feed↗
PubMed1987

The effects of feeding either hay or grass diets on salivary phosphorus secretion, net intestinal phosphorus absorption and on the partition of phosphorus excretion between urine and faeces in the sheep.

Mature sheep fitted with ruminal and duodenal cannulas were fed either a pelleted hay or a pelleted grass diet with or without supplementary phosphorus. Salivary phosphorus secretion, net intestinal phosphorus absorption and the route of phosphorus excretion were determined. The route of excretion was markedly affected by diet with urinary excretion being much higher and faecal excretion lower when the grass diet was fed. These effects were not due to differences in phosphorus intake or to differences in net intestinal phosphorus absorption. Salivary phosphorus secretion was, however, lower when the grass diet was fed. The significance of these changes in relation to the control of phosphorus balance in ruminants is discussed.

Animal Feed↗
PubMed1984

Influence of phase feeding available phosphorus on egg production characteristics, carcass phosphorus content, and serum inorganic phosphorus levels of three commercial layer strains.

An experiment was conducted to obtain information on the concept of progressively decreasing dietary phosphorus levels (phase feeding) on the performance of three different commercial layer strains. Dietary available phosphorus (AP) levels of .15, .30, or .45% were fed continuously from 22 to 70 weeks of age. Concurrently, a diet containing .35, .25, and .15% AP was phase-fed during age intervals of 22 to 34, 34 to 50, and 50 to 70 weeks, respectively. Dietary AP levels did not significantly affect egg production except the .15% AP level, which significantly reduced egg production when compared with the other three dietary AP treatments. Efficiency of feed utilization was significantly superior for hens phase-fed AP compared with hens fed the other AP treatments. There were no differences in egg weight or mortality due to dietary AP. Eggshells were significantly thicker when hens received .15% AP. The .15% AP and phase-fed regimen resulted in hens with significantly lower body weights at the end of the experiment. Hens fed .30% AP and phase-fed AP had significantly lower carcass ash and phosphorus levels. Serum phosphorus levels corresponded directly to dietary AP levels. There were no significant differences in egg production due to strain nor were there any strain by dietary treatment interactions that influenced production traits. Significant strain differences were noted in feed efficiency, egg weight, carcass ash, and carcass phosphorus.

Animal Feed↗
PubMed2002

Phosphorus-calcium carbonate saturation relationships in a lowland chalk river impacted by sewage inputs and phosphorus remediation: an assessment of phosphorus self-cleansing mechanisms in natural waters.

The relationship between calcium carbonate saturation and phosphorus concentrations for seven sites on the upper reaches of the River Kennet are examined. The findings are related to issues of groundwater supplies and the introduction of phosphorus treatment of effluent from the Marlborough sewage treatment works (STW) at part of the way along the study reach. Being supplied from a Cretaceous Chalk aquifer, the Kennet is mainly of a calcium-bicarbonate type and has a relatively constant composition of many major water quality determinands. Typically, the waters average a pH of approximately eight (range approx. 7.5-8.5) during the day with the lowest values occurring at the upstream site. Dissolved carbon dioxide varies from approximately 5 to 35 times atmospheric pressure during the late morning with the highest values occurring at the upstream site. However, in-stream biological activity gives rise to marked diurnal fluctuations in pH and dissolved carbon dioxide concentrations and during the summer months, by mid to late afternoon, pH is at its maximum and dissolved carbon dioxide is at its lowest: this is shown by continuous measurements at one of the river sites. Alkalinity and calcium concentrations remain relatively constant at approximately 4,700 microEq/l (range 3,500-6,000 microEq/l) and 120 mg/l (range 85-150 mg/l), respectively, and the waters are oversaturated with respect to calcium carbonate (calcite) typically by a factor of six (range 2-25). Along the reach, soluble reactive phosphate (SRP) increases from the first to the second site with the introduction of sewage supplies from the Marlborough STW, and then declines further downstream as sewage dilution and uptake by the river bed/aquatic plants increases. The differences in concentration decrease after phosphorus removal from Marlborough STW. Despite this change, there is no clear indication of any calcite solubility control except perhaps at times of extreme baseflow during the growing season when within-stream photosynthesis is maximal and within-stream residence times are longer. A comparison of river and groundwater data shows that the groundwaters have similar alkalinities and calcium concentrations. However, the groundwaters have (a) higher carbon dioxide saturations (a factor of 2-5 times the value for the river), (b) lower pHs (0.5-1.5 units), (c) lower SRP concentrations (a quarter or less of the river values) and (d) waters near calcite saturation (unlike the surface waters which are oversaturated). The findings indicate a river system dominated by the input carbon dioxide laden groundwaters in approximate equilibrium with calcite attenuated by within-channel biological and physical processes. Within the river: (a) the waters degas carbon dioxide increasing the pH, producing oversaturated conditions; and (b) oscillating pH-dissolved carbon dioxide levels occur between day and night due to changing balances between photosynthesis and respiration. It seems that lowering the phosphorus levels have not resulted in calcite precipitation within the water column and that no significant within-stream self-cleansing mechanisms are occurring that might be predicted from theory: other components in the water such as dissolved organic carbon may inhibit calcite nucleation. However, the low SRP levels in the groundwater coupled with calcite saturation, may well indicate that phosphorous concentrations within the groundwater are regulated by such processes: the number of calcite nucleating sites are orders of magnitude higher and the calcite inhibitors may be less prevalent.

Calcium Carbonate↗
PubMed1999

The course of phosphorus excretion in growing pigs fed continuously increasing phosphorus concentrations after a phosphorus depletion.

A balance study was performed in order to quantify the effect of continuously increased phosphorus (P) intake on faecal and urinary P excretion. The aim was to quantify the level of intake where regulatory P excretion becomes relevant for comparative digestibility measurements on P, and when the pig adapts its urinary P excretion to increased P intake. Phosphorus intake of growing pigs was continuously increased on a daily basis starting at a marginal level and P excretion via faeces and urine was continuously followed for 92 days. Two semi-synthetic diets were prepared with different proportions of Na2HPO4 resulting in 2.4 (diet 1) and 6.3 (diet 2) g P/kg DM. Concentration of Ca was adapted to achieve a Ca supply approximately 3.1 fold the digestible P supply. Six castrated male crossbred pigs (31 kg BW) were kept individually in metabolism crates after they had undergone a 14 d P depletion period during which they were fed diet 1 solely. Pigs received 1.04kg of diet 1 per day throughout the experiment, and each day the amount of feed and P supplied to pigs from diet 2 was increased by 12 g and 69 mg, respectively. ME supply was approximately 2.4 fold maintenance and average daily BW gain of pigs during the entire experiment was 690 +/- 30 g. While intake increased linearly, faecal excretion of P and Ca increased non-linearly and could be best described by third order polynomial functions. The proportion of ingested P not excreted via faeces followed a quadratic type of curve with a maximum of 81% at 25 days on experiment and P intake of 4.0 g/d. Thereafter, the proportion decreased continuously. The digestibility of P from diet 2, determined by the slope ratio technique, was constant and not affected by P intake up to a P intake of 5 g/d. Renal P excretion did not exceed inevitable losses until day 60 and increased exponentially thereafter when body P reserves were restored. It is concluded, that an adaptation to surplus P supply occurred earlier on the intestinal than on the renal level. While faecal P excretion appeared regulated depending on the actual requirement for P retention, the regulation via urine depended on the P status of the pig. Once the renal P excretion of growing pigs exceeds a level of 25 mg/d, intake of digestible P cannot be regarded sufficiently low to measure P digestibility as a capacity of the feedstuff.

Absorption↗
PubMed1987

Dietary intake of phosphorus modulates the circadian rhythm in serum concentration of phosphorus. Implications for the renal production of 1,25-dihydroxyvitamin D.

We recently reported that in healthy men, changes in the production rate (PR) of 1,25-dihydroxyvitamin D [1,25-(OH)2D] accounted for the 80% increase and the 30% decrease in its serum concentration that was induced by restriction and supplementation, respectively, of dietary phosphorus. These changes in PR and serum concentration of 1,25-(OH)2D could be mediated by changes in serum concentrations of phosphorus that occur after the morning fasting period. To examine this hypothesis, we measured serum concentrations of phosphorus in blood drawn at hourly intervals for 24 h in six healthy men in whom dietary phosphorus was initially maintained at 1,500 mg/70 kg body weight per day for 9 d, then restricted to 500 mg/d (coupled with orally administered aluminum hydroxide) for 10 d, and then supplemented to 3,000 mg/d for 10 d. When dietary phosphorus was normal, the serum concentration of phosphorus exhibited the normal circadian rhythm: a rapid decrease in early morning to a nadir at 1100, followed by an increase to plateau at 1600 h and a further increase to an acrophase (peak) at 0030 h. The variation in serum levels of phosphorus can be described as the sum of sinusoidal functions with periodicities of 24 and 12 h. Phosphorus restriction for 10 d induced a 40% reduction in the 24-h mean serum level of phosphorus, abolished the early afternoon rise in its serum level (i.e., the 12-h periodic component of the time series), and delayed the acrophase by 3 h to 0330 h. Phosphorus supplementation for 10 d induced a 14% increase in the 24-h mean serum level of phosphorus but no significant change in its morning fasting level, exaggerated the early afternoon rise in serum phosphorus, and advanced the acrophase by 9 h to 1530 h. The changes in the PR of 1,25-(OH)2D induced by restriction and supplementation of dietary phosphorus varied inversely and significantly with those induced in the 24-h mean serum level of phosphorus (R = -0.88, P less than 0.001). These data demonstrate that in healthy men, dietary phosphorus is an important determinant of the serum concentration of phosphorus throughout most of the day. The data suggest that diet-induced changes in serum levels of phosphorus mediate the changes in PR and serum concentration of 1,25(OH)2D.

Adult↗
PubMed1994

Effects of a change in phosphorus requirement on phosphorus kinetics in the sheep.

An experiment was carried out to examine the effects of a change in P requirement, achieved by intravenous calcium loading, on intestinal phosphorus absorption, salivary phosphorus secretion and faecal endogenous phosphorus loss in adult sheep fitted with a rumen and duodenal cannula. Isotope dilution was used to measure faecal endogenous phosphorus loss while 103ruthenium phenanthroline and 51chromium-ethylenediamine tetra-acetic acid were used to measure duodenal phosphorus flow. The infusion of calcium chloride led to an increase in calcium and phosphorus retention, the increase in phosphorus retention being due to a reduction in faecal phosphorus excretion as a result of enhanced intestinal phosphorus absorption and reduced faecal endogenous phosphorus excretion. There was, however, no change in duodenal phosphorus flow or in the amount of phosphorus estimated to have been added to the digesta via the saliva. These results suggest that the increase in phosphorus retention seen in response to an increase in phosphorus requirement is largely achieved through an increase in intestinal absorptive efficiency and not through any reduction in endogenous phosphorus secretion into the gut.

Animals↗
PubMed2001

Dietary phosphorus supply, egg-shell deposition and plasma inorganic phosphorus in laying hens.

1. In 2 experiments the effects of dietary phosphorus on relationships between plasma inorganic phosphorus concentration (Pi), shell and egg production and depletion states were measured in brown laying hens. 2. In a 12-week experiment dietary phosphorus concentrations from conventionally deficient (1.6 g non-phytate-phosphorus (PNP)/kg) to moderate excess (3.9 g PNP/kg) had little effect on egg and shell production, although there was evidence that plasma Pi concentration, when not influenced strongly by shell formation, reflected dietary phosphorus content. 3. Among birds at each dietary phosphorus concentration there was a negative linear relationship between shell weight of early eggs in the sequence and plasma Pi concentration. The relationship was apparently not affected by dietary phosphorus concentration. 4. Continued feeding of the deficient diet to 61 weeks of age did not have effects on body weight, egg and shell production, other than those associated with age, but plasma Pi and bone measurements indicated marginal phosphorus depletion. 5. In another experiment excessive dietary phosphorus (11.9 g PNP/kg) fed in a cross-over design caused small adverse effects on shell production, increased food intake and body weight and increased plasma Pi content, while there was no relationship between shell weight and plasma Pi concentration. 6. The results are consistent with an indirect effect of plasma phosphorus accumulation on shell formation, probably via an inhibitory effect on skeletal calcium release, in addition to any effect of excess dietary phosphorus on intestinal calcium availability. 7. Phosphorus requirement and status in the laying hen are complicated by the failure to recognise the contribution of digestible phytate-phosphorus to the available phosphorus supply.

Animal Feed↗
PubMed1979

Effects of different short-term dietary phosphorus levels on egg specific gravity and blood phosphorus of hens.

In the first 2 experiments, laying hens were fed a diet containing .30% phosphorus for a preliminary period of 3 days. At the beginning of the experimental period, hens were fed .30, .75, or 1.40% phosphorus with 3.50% calcium. Another group of hens was fed .75% phosphorus and 1.40% calcium. Specific gravity of the eggs and blood serum inorganic phosphorus were determined and compared with those from control hens continuously fed a diet containing .75% phosphorus and 3.50% calcium. Both high phosphorus and/or low calcium decreased the specific gravity of eggs and increased the serum phosphorus level. In experiment 2, hens were fed different levels of phosphorus at different times of the day. Birds receiving 1.40% phosphorus between 0700 and 0930 hr and .30% phosphorus between 0930 and 2000 hr (Treatment 2) laid eggs with higher specific gravity than hens fed .30% phosphorus between 0700 and 0930 hr and 1.40% phosphorus between 0930 and 2000 hr (Treatment 3). there was no further improvement in egg shell quality over that from hens fed .75% phosphorus for both time periods (0700 to 2000 hr). In both experiments it was apparent that the dietary phosphorus level affected egg shell quality.

Animals↗
PubMed1979

The phosphorus excretion pattern and balance during one egg cycle of the laying hen fed a phosphorus deficient diet with or without a single dose of phosphoric acid.

A balance trial was conducted to study the phosphorus excretion pattern of laying hens in relation to egg cycle. Excreta were collected quantitatively at 4, 8, 12, and 24 hr after oviposition. The amount of feed consumed corresponding to the excreta collected at a specific time interval was calculated using chromic oxide as a marker. The percent recovery of chromic oxide with laying hens was 73.97 +/- .56%. The maximum apparent digestibility of the dietary phosphorus, all of plant origin, was estimated to be 28.9 +/- 3.1% during 0 to 4 hr after oviposition when the endogenous excretion of phosphorus was theoretically minimized. Laying hens fed a diet containing .30% phosphorus excreted 24.3 mg less phosphorus than intake during the day, indicating that hens had to withdraw approximately 100 mg of phosphorus from their body to produce an egg. These hens excreted 63.1 +/- 27.0 mg of endogenous phosphorus during the 24 hr period, most of which was excreted during the period between 12 to 24 hr after oviposition of the previous egg. The excretion pattern of phosphorus was closely related to the egg laying cycle of the hen. Hens dosed with 100 mg of phosphorus, as a phosphoric acid solution, excreted more phosphorus than the undosed control birds. Approximately 45 mg of 100 mg of the phosphorus dose were excreted during the 24 hr period. At least 84.8 mg of the dosed phosphorus were absorbed within 12 hr and a part of it was excreted during the later period. Data indicated that the true absorption rate of the dosed phosphorus might have been much faster.

Animal Feed↗