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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. [ABSTRACT FROM AUTHOR]

ABSTRACT: Efforts to achieve sustainable phosphorus (P) inputs in broiler farming which meet the physiological demand of animals include nutritional intervention strategies that have the potential to modulate and utilize endogenous and microbiota-associated capacities. A temporal P conditioning strategy in broiler nutrition is promising as it induces endocrinal and transcriptional responses to maintain mineral homeostasis. In this context, the current study aims to evaluate the composition of the jejunal microbiota as a functional entity located at the main absorption site involved in nutrient metabolism. Starting from a medium or high P supply in the first weeks of life of broilers, a depletion strategy was applied at growth intervals from d 17 to 24 and d 25 to 37 to investigate the consequences on the composition of the jejunal microbiota. The results on fecal mineral P, calcium (Ca), and phytate contents showed that the diets applied to the depleted and non-depleted cohorts were effective. Microbial diversity in jejunum was represented by alpha diversity indices which appeared unaffected between dietary groups. However, chickens assigned to the dietary P depletion groups showed significantly higher abundances of Facklamia, Lachnospiraceae, and Ruminococcaceae compared to non-depleted control groups. Based on current knowledge of microbial function, these microorganisms make only a minor contribution to the birds' adaptive mechanism in the jejunum following P depletion. Microbial taxa such as Brevibacterium, Brachybacterium, and genera of the Staphylococcaceae family proliferated in a P-enriched environment and might be considered biomarkers for excessive P supply in commercial broiler chickens.

Phosphorus metabolism in laying hens is a highly dynamic process over the course of the 24 h egg-laying cycle. Adjusting the phosphorus feeding regimen according to the daily egg-laying cycle may help to improve phosphorus utilization efficiency. Hy-Line Brown layers (n = 120; 70 wk old) were offered 4 different phosphorus daily regimens: (1) RR, fed regular phosphorus at both 09:00 and 17:00; (2) RL, fed regular phosphorus at 09:00 and low phosphorus at 17:00; (3) LR, fed low phosphorus at 09:00 and regular phosphorus at 17:00; (4) LL, fed low phosphorus at both 09:00 and 17:00. The regular and low phosphorus diets contained 0.32% and 0.14% non-phytate phosphorus, respectively. The feeding trial lasted for 12 wk. As a result, layers on the RL regimen had decreased laying rate (P 0.05); (2) decreased phosphorus excretion (P

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.

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The intensity of oxygen consumption and the rate of phosphorus excretion are studied in planktonic crustaceans Daphnia longispina O.F. Müller (Cladocera), benthic crustaceans Hyalella azteca (Saussure) (Amphipoda), and fish Oryzias latipes (Temminck & Schlegel) (Beloniformes) united in one trophic net in an experimental ecosystem. The highest rates of metabolic intensity are established for small organisms Daphnia longispina (7.44 ± 2.49 mgO/(g h) and 0.447 ± 0.143 mgP/(g h)). The rate of phosphorus excretion differed by an order of magnitude between hydrobionts of different ecological groups and decreased in the order planktonic crustaceans –> benthic crustaceans –> fish. It is shown that the contribution of hydrobionts to the creation of primary production depends on the biomass of a particular species. [ABSTRACT FROM AUTHOR]

Recent technological advances make it possible to deliver feeding strategies that can be tailored to the needs of individual pigs in order to optimise the allocation of nutrient resources and contribute toward reducing excess nutrient excretion. However, these efforts are currently hampered by the challenges associated with: (1) estimation of unobserved traits from the available data on bodyweight and feed consumption; and (2) characterisation of the distributions and correlations of these unobserved traits to generate accurate estimates of individual level variation among pigs. Here, alternative quantitative approaches to these challenges, based on the principles of inverse modelling and separately inferring individual level distributions within a Bayesian context were developed and incorporated in a proposed precision feeding modelling framework. The objectives were to: (i) determine the average and distribution of individual traits characterising growth potential and body composition in an empirical population of growing-finishing barrows and gilts; (ii) simulate the growth and excretion of nitrogen and phosphorus of the average pig offered either a commercial two-phase feeding plan, or a precision feeding plan with daily adjustments; and (iii) simulate the growth and excretion of nitrogen and phosphorus across the pig population under two scenarios: a two-phase feeding plan formulated to meet the nutrient requirements of the average pig or a precision feeding plan with daily adjustments for each and every animal in the population. The distributions of mature bodyweight and ratio of lipid to protein weights at maturity had median (IQR) values of 203 (47.8) kg and 2.23 (0.814) kg/kg, respectively; these estimates were obtained without any prior assumptions concerning correlations between the traits. Overall, it was found that a proposed precision feeding strategy could result in considerable reductions in excretion of nitrogen and phosphorus (average pig: 8.07 and 9.17% reduction, respectively; heterogenous pig population: 22.5 and 22.9% reduction, respectively) during the growing-finishing period from 35 to 120 kg bodyweight. This precision feeding modelling framework is anticipated to be a starting point toward more accurate estimation of individual level nutrient requirements, with the general aim of improving the economic and environmental sustainability of future pig production systems.

Across the equine literature, estimates of true P digestibility range from −23% to 79%. This large range cannot be explained by differences in P intake or phytate‐P intake alone. However, differences in endogenous P secretion into the GI tract may explain the variation. In horses, excess absorbed P is not excreted in the urine but is re‐secreted into the GI tract, increasing faecal P and leading to estimates of low P digestibility. Thus, accurate estimates of P digestibility can only be obtained if absorbed P is retained in the horse. The objective of this study was to examine P digestibility in post‐lactational mares and control mares that were fed similar amounts of P. It was hypothesized that post‐lactational mares would have greater P retention and higher apparent P digestibility than control mares. Prior to the study, four lactating and four non‐lactating mares were fed a diet that provided 100% of the control mares' P requirement, but only 55% of the lactating mares' P requirement. During the study, both groups were fed P at the rate recommended for non‐lactating mares. Post‐lactational mares did not retain more P than control mares but tended to excrete more P than control mares (p =.082), presumably due to differences in endogenous P secretion into the GI tract. Metabolic changes occurring during mammary gland involution may have contributed to the increase in P excretion. However, faecal P excretion exceeded P intake in both groups (p =.08) and both groups lost weight during the study. Tissue mobilization during weight loss may have influenced P secretion into the GI tract. [ABSTRACT FROM AUTHOR]

The influence of nano-hydroxyapatite (NHA) as a source of calcium (Ca) and phosphorous (P) alternative to inorganic dicalcium phosphate (DCP) on the performance, carcass traits, and the Ca and P contents in serum, bone, and excreta was evaluated in broiler chickens. One-day-old un-sexed Arbor Acres Plus broiler chickens (n.= 160) were randomly assigned to four treatment groups of four replicates with 10 birds in each replicate. The birds received, for 35 days, one of four isocaloric isonitrogenous experimental diets differing in DCP and NHA inclusion levels as follows: diet 1 served as control and contained 2% DCP (100% DCP); diet 2 contained 1% DCP plus 0.1% NHA (50% DCP); diet 3 having 0.5% DCP plus 0.1% NHA (25% DCP); diet 4 having a 0.1% NHA only (0% DCP). The NHA was prepared by the wet chemical method and was shown to have Rod-like shape with 20-100 nm size, 98% purity, 30.8% Ca and 11% available P. Results indicated that the dietary supplementation of 0.5% DCP plus 0.1% of NHA (diet 3) or 0.1% of NHA (diet 4) decreased the excreted P (P = 0.05) without negative impacts on growth performance parameters compared to control group. There was no difference (P > 0.05) in the carcass characteristics and serum Ca-P profile of broilers among the four dietary treatments. There was no difference (P > 0.05) in the tibia bone ash as well as the Ca and P levels among experimental diets. Thus, dietary supplementation of 0.1% of NHA can be safely used instead of inorganic DCP in broiler diets. [ABSTRACT FROM AUTHOR]

Background: Dietary supplemental nicotinamide is used to treat hyperphosphatemia in humans. However, the mechanisms of its impact on body phosphorus homeostasis remain unclear.Objective: This study was to determine effects and molecular mechanisms of 3 dietary nicotinamide concentrations on body phosphorus homeostasis in laying hens.Methods: Hy-Line Brown layers (total = 21; 40 wk old; body weight: 1,876 ± 24 g) were individually housed (n = 7) and fed a corn-soybean meal-based diet supplemented with nicotinamide at 20 (N20), 140 (N140), and 1000 (N1000) mg/kg for 21 d. Serum phosphorus and fibroblast growth factor 23 (FGF23) concentrations, phosphorus and calcium excretion, and mRNA and/or protein of type II sodium-phosphate co-transporters (NPt2a, NPt2ab) and FGF23 and FGF23 receptors were measured in the intestines, calvaria, kidney, and liver.Results: Hens in the N1000 group had a 16% lower serum phosphorus concentration and 22% greater phosphorus excretion than those in the N20 or N140 group (P ≤ 0.05). Compared with hens in the N20 group, hens in the N140 and N1000 groups, which did not differ, had 15-21% lower serum FGF23 concentrations, 19-22% greater calcium excretion, 43-56% lower ileum NPT2b protein production, and 1.5- to 1.6-fold greater kidney NPT2a protein production, respectively (all differences at P ≤ 0.05).Conclusions: Supplementing high concentrations of nicotinamide in diets for laying hens led to accelerated phosphorus and calcium excretions and decreased serum phosphorus and FGF23 concentrations, which were associated with downregulated intestinal NPt2b protein production. Our findings exclude kidney NPt2a protein production as a primary mechanism for the nicotinamide-induced body phosphorus loss. [ABSTRACT FROM AUTHOR]

Efforts to achieve sustainable phosphorus (P) inputs in broiler farming which meet the physiological demand of animals include nutritional intervention strategies that have the potential to modulate and utilize endogenous and microbiota-associated capacities. A temporal P conditioning strategy in broiler nutrition is promising as it induces endocrinal and transcriptional responses to maintain mineral homeostasis. In this context, the current study aims to evaluate the composition of the jejunal microbiota as a functional entity located at the main absorption site involved in nutrient metabolism. Starting from a medium or high P supply in the first weeks of life of broilers, a depletion strategy was applied at growth intervals from d 17 to 24 and d 25 to 37 to investigate the consequences on the composition of the jejunal microbiota. The results on fecal mineral P, calcium (Ca), and phytate contents showed that the diets applied to the depleted and non-depleted cohorts were effective. Microbial diversity in jejunum was represented by alpha diversity indices which appeared unaffected between dietary groups. However, chickens assigned to the dietary P depletion groups showed significantly higher abundances of Facklamia, Lachnospiraceae , and Ruminococcaceae compared to non-depleted control groups. Based on current knowledge of microbial function, these microorganisms make only a minor contribution to the birds' adaptive mechanism in the jejunum following P depletion. Microbial taxa such as Brevibacterium, Brachybacterium , and genera of the Staphylococcaceae family proliferated in a P-enriched environment and might be considered biomarkers for excessive P supply in commercial broiler chickens. [ABSTRACT FROM AUTHOR]

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 < 0.001 for fecal phosphorus excretion and r = 0.78 and P < 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 < 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 < 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. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effects of reducing dietary phosphorus (P) on the frame size, udder traits, blood parameters and nutrient digestibility coefficient in 8- to 10-month-old Holstein heifers. Forty-five heifers were divided into 15 blocks according to the mo of age and were randomly assigned one of three dietary treatments: 0.26% (low P [LP]), 0.36% (medium P [MP]), or 0.42% (high P [HP]) (dry matter basis). Samples were collected at the wk 1, 4, 8. The results show that low dietary P had no effect on body measurement. The blood P concentration decreased with decreasing dietary P (p

There is a global imperative to reduce phosphorous (P) excretion from pig systems. In this study, a previously validated deterministic model was modified to be stochastic, in order to investigate the consequences of different management strategies on P excretion by a group of growing pigs. The model predicts P digestion, retention and excretion from feed composition and growth parameters that describe a specified pig phenotype. Stochasticity was achieved by introducing random variation in the latter. The strategies investigated were: (1) changing feed composition frequently in order to match more closely pig digestible P (digP) requirements to feed composition (phase feeding) and (2) grouping pigs into light and heavy groups and feeding each group according to the requirements of their group average BW (sorting). Phase feeding reduced P excretion as the number of feeding phases increased. The effect was most pronounced as feeding phases increased from 1 to 2, with a 7.5% decrease achieved; the increase in phases from 2 to 3 was associated with a further 2.0% reduction. Similarly, the effect was more pronounced when the feed targeted the population requirements for digP at the average BW of the first third, rather than the average requirements at the mid-point BW of each feeding sequence plan. Increasing the number of feeding phases increased the percentage of pigs that met their digP requirements during the early stages of growth and reduced the percentage of pigs that were supplied

Abstract: BACKGROUND: The effect of phytase supplementation with respect to a high sorghum grain diet on sheep voluntary feed intake, apparent nutrient digestibility, ruminal fermentation, phosphorus (P) excretion and blood serum P concentration was evaluated. RESULTS: Phytase supplementation significantly decreased fecal P excretion (P = 0.003), resulting in a 26% decrease in relation to the phytase free diet. Dry matter intake, nutrient digestibility, ruminal butyrate and serum P were not (P > 0.10) affected by the phytase level. Neutral detergent digestibility showed a tendency to increase linearly (P = 0.10) with increasing phytase levels. Ruminal pH was lower for phytase supplemented sheep, with a significant decrease (P = 0.007) at 9 h post feeding, whereas ruminal ammonia‐N at 3 h post feeding was lower (P = 0.004) for the phytase treatment groups, resulting in a decreasing linear response (P = 0.001) with an increasing phytase dose. Duodenal pH was significantly reduced at 6 h post feeding. Propionate tended (P = 0.051) to be increased linearly as the phytase supplementation level increased. CONCLUSION: Exogenous phytase supplementation of high sorghum grain diets significantly decreased fecal P excretion in Rambouillet rams. Phytase supplementation appears to affect neutral detergent fiber digestibility, duodenal and ruminal pH, ammonia and propionate. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The objective of the study was to evaluate the effect of inorganic phosphorus (Pi) infusion on P absorption in large intestine, milk production, and phosphorus excretion. Four ruminally and ileally cannulated crossbred cows were used in a 4 × 4 Latin square with 21-d periods. Cows were fed a total mixed ration containing 0.21% P, providing 50% of the cows' P requirement. Cobalt-EDTA was used as marker to measure large intestine digesta flow. On d 13 to 21 of each period, each cow was infused daily with 0, 20.1, 40.2, or 60.3 g of Pi into the abomasum and total collection was conducted on d 18 to 21. Ileal samples were collected every 9 h on d 18 to 21. Feed, digesta, and fecal samples were analyzed for total P and Pi using the molybdovanadate yellow method and blue method, respectively. All data were analyzed using PROC GLIMMIX in SAS 9.3 (SAS Institute Inc., Cary, NC) using contrasts to evaluate linear, quadratic, and cubic effects of Pi infusion dose. Dry matter intake, apparent dry matter digestibility, milk yield, and milk total P were unaffected by Pi infusion. Ileal flow and fecal excretion of total P and Pi increased linearly with increasing infused Pi. In the large intestine, net absorption of TP and Pi was increased linearly with increasing infused Pi. The magnitude of absorption from the large intestine was greater than reflected in current models, raising questions that could be evaluated with longer infusion periods or dietary alteration. [ABSTRACT FROM AUTHOR]

Objective: specify peculiarities of calcium and phosphates excretion in neonates of various gestational ages and types of feeding in neonatal period. Patients and methods. Calcium-creatinine (Ca/Cr) and phosphate-creatinine (P/Cr) ratio concentrations were determined in 96 healthy neonates of 38-40 weeks of gestational age and 146 premature infants of 28-37 weeks of gestational age of various types of feeding. Results. The Ca/Cr ratio concentration in healthy term infants in the early neonatal period amounted to 0.9-2.2 (median – 1.8), the P/Cr ratio concentration – 0.8-2.1 (median – 1.6). The Ca/Cr ratio concentration in premature infants (28-37 weeks of gestational age) amounted to 0.9-2.4 (median – 1.9), which is comparable to this parameter’s value in term infants. The P/Cr ratio concentration amounted to 0.7-3.1 (median – 2.4), which exceeds this parameter’s value in term infants. The lesser the gestational age and birth weight, the higher the Ca/Cr and P/Cr ratio concentrations. The authors revealed hypercalciuria and hyperphosphaturia in premature infants with a very low body weight fed with specialized formulas. Conclusions. Use of specialized formulas in small premature infants (gestational age < 33 weeks) with VLBW results in excessive calcium and phosphates excretion. It is reasonable to monitor their concentrations using a non-invasive and informative method of determining Ca/Cr and P/Cr ratios. Feeding of premature infants with BW > 1,500 g with breast milk only (in case of the mother’s adequate lactation) allows avoiding hypercalciuria and hyperphosphaturia and preventing risk of a renal pathology.

Seston availability and quality can affect the condition, nutrient stoichiometry and nutrient excretion of dreissenid mussels and other aquatic consumers. Nutrient excretion by dreissenid mussels may affect phytoplankton community composition by altering nitrogen:phosphorus (N:P) ratios of the water and may be an important accessory factor leading to increased Cladophora and toxic Microcystis blooms in mussel-invaded lakes., We manipulated phosphorus enrichment levels [no (L), moderate (M) and high (H)] and zebra mussel concentrations (1, 2 and 4 g dry mass m−2) to produce a total of nine treatment combinations, each one held in a 31 m3 enclosure in an oligotrophic lake. We measured zebra mussel condition, carbon:nitrogen:phosphorus (C:N:P) tissue stoichiometry, feeding rate and nutrient excretion and egestion as related to varying conditions of chlorophyll a (Chl), particulate phosphorus ( PP), particulate organic nitrogen ( PON) and seston C:N:P ratios at three time periods: 5-7, 18-20 and 32-34 days subsequent of adding mussels to the enclosures., Consistent with approximate homeostatic control of N and P, there were only modest differences in C:N:P ratios in mussel soft tissue despite greatly different seston C:N:P ratios among enrichment treatments. Mussel condition (mass per unit length) decreased with increased seston N:P, C:P and C:N ratios and percent composition of Cyanobacteria, and increased with percentage composition of cryptophytes and other flagellates., Assimilation rates of Chl and calculated potential assimilation rates of N and P linearly increased ( P < 0.05) with increasing seston Chl, PON and PP concentrations., P excretion measured as soluble reactive phosphorus ( SRP) significantly decreased in exponential fashion by two orders of magnitude as C:P ( R2 = 0.71) and N:P ratios ( R2 = 0.66) increased by a factor of 4. P excretion was significantly correlated with seston PP concentration, which varied over a 19-fold range; however, there was much scatter in the relationship ( R2 = 0.29). In contrast, NH4-N excretion significantly decreased ( R2 = 0.31) with N:P ratio by a factor of 2 over this same N:P range, and was not significantly correlated with PON concentration. Soluble P excretion was significantly correlated with potential P assimilation, whereas NH4 excretion was not significantly correlated with potential N assimilation. The ratio of N:P excreted showed a significant exponential increase with seston N:P ratio., P and N egestion rates were higher than corresponding P and N excretion rates from the same trials; however, the fate of this egested material - whether recycled by resuspension or remaining in the benthos - is not known., Mussel excretion and its impacts are highly context dependent, varying with algal composition, seston stoichiometry, and mussel abundance and feeding rate. The low P excretion but high N excretion observed when mussel feeding stops implies that under poor feeding conditions typical of summer seston, mussels excrete little P but continue excreting N, which would slow production rate of producers such as Cladophora and Microcystis in low-P systems. In contrast, NH4 excretion by mussels may prolong Microcystis blooms as nitrate is used up by the bloom in moderate-P systems. [ABSTRACT FROM AUTHOR]

Five hundred and four 1-day-old Cobb broiler chickens were randomly allotted to 18 treatments and fed a semi-purified basal diet (4 g/kg total phosphorus) supplemented with 2 levels of supplemental P (0.5 or 1 g/kg) during 21 days to evaluate performance and bone mineralization; to assess the relative bioavailability of P (RBP) in wheat meal (WM) and roasted (RS) or extruded soybean meal (ES), with or without phytase (0 or 750 ftu/kg diet), using dicalcium phosphate (DC) as standard; and to estimate phosphorus excretion. Weight gain (WG), feed intake (FI), feed to gain ratio (FG), and tibia ash weigh (AW) were assessed. For each source, the RBP was calculated by the slope ratio method, when tibia ash weight was regressed on P ingested. Ingested and fecal P was determined to calculate P intake, and P excretion and excretion rate. Phytase addition increased overall FI, WG, and FG ratio by 3.3, 2.6 and 0.8%, respectively, but differences were not significant. Overall AW was increased by 10.8% after the enzyme inclusion in the diets. The relative bioavailability of phosphorus values of tested WM, RS, and ES were increased by 6.32, 64.32, 76.99%, respectively, in response to supplementation of phytase in diets containing WM, RS, and ES, respectively. Phytase reduced P excretion by 12.7% and the excretion rate by 15.0%, regardless of the phosphorus source or level.

The objective of this study was to investigate the effects of reducing dietary phosphorus (P) on the frame size, udder traits, blood parameters and nutrient digestibility coefficient in 8- to 10-month-old Holstein heifers. Forty-five heifers were divided into 15 blocks according to the mo of age and were randomly assigned one of three dietary treatments: 0.26% (low P [LP]), 0.36% (medium P [MP]), or 0.42% (high P [HP]) (dry matter basis). Samples were collected at the wk 1, 4, 8. The results show that low dietary P had no effect on body measurement. The blood P concentration decreased with decreasing dietary P (p<0.05), while the blood calcium content of LP was higher than that of the MP and HP groups (p<0.05), though still in the normal range. The serum contents of alkalinephosphatase, potassium, and magnesium were similar among the treatments. No differences were found in all nutrients' apparent digestibility coefficients with varied dietary P. However, with P diet decreased from HP to LP, the total fecal P and urine P concentration declined significantly, as did fecal water soluble P (p<0.05). In conclusion, reducing the dietary P from 0.42% to 0.26% did not negatively affect the heifers' growth performance but did significantly lessen manure P excretion into the environment. [ABSTRACT FROM AUTHOR]

There is a global imperative to reduce phosphorous (P) excretion from pig systems. In this study, a previously validated deterministic model was modified to be stochastic, in order to investigate the consequences of different management strategies on P excretion by a group of growing pigs. The model predicts P digestion, retention and excretion from feed composition and growth parameters that describe a specified pig phenotype. Stochasticity was achieved by introducing random variation in the latter. The strategies investigated were: (1) changing feed composition frequently in order to match more closely pig digestible P (digP) requirements to feed composition (phase feeding) and (2) grouping pigs into light and heavy groups and feeding each group according to the requirements of their group average BW (sorting). Phase feeding reduced P excretion as the number of feeding phases increased. The effect was most pronounced as feeding phases increased from 1 to 2, with a 7.5% decrease achieved; the increase in phases from 2 to 3 was associated with a further 2.0% reduction. Similarly, the effect was more pronounced when the feed targeted the population requirements for digP at the average BW of the first third, rather than the average requirements at the mid-point BW of each feeding sequence plan. Increasing the number of feeding phases increased the percentage of pigs that met their digP requirements during the early stages of growth and reduced the percentage of pigs that were supplied <85% of their digP requirements at any stage of their growth; the latter may have welfare implications. Sorting of pigs reduced P excretion to a lesser extent; the reduction was greater as the percentage of pigs in the light group increased from 10% to 30% (from 1.5% to 3.0% reduction, respectively). This resulted from an increase in the P excreted by the light group, accompanied by a decrease in the P excreted by the remaining pigs. Sorting increased the percentage of light pigs that met their dig P requirements, but only slightly decreased the percentage of heavy pigs that met these requirements at any point of their growth. Exactly the converse was the case as far as the percentage of pigs that were supplied <85% of their digP requirements were concerned. The developed model is flexible and can be used to investigate the effectiveness of other management strategies in reducing P excretion from groups of pigs, including precision livestock feeding. [ABSTRACT FROM AUTHOR]

Introduction. The Western diet is associated with high consumption of processed foods preserved with phosphate. Higher dietary phosphate consumption stimulates production of fibroblast growth factor 23 (FGF23), which heightens risk for cardiovascular disease and mortality. We hypothesized that adults living in a more westernized society have higher levels of FGF23 due to increased phosphate consumption as measured by urinary phosphate excretion. Methods. We measured plasma C-terminal FGF23 levels and urinary phosphate and creatinine levels in timed urine collections among 100 African adults living in the rural area of Igbo-Ora, Nigeria (52 women, 48 men), and 100 African Americans (32 women, 68 men) living in Maywood, IL, an significantly higher in Maywood versus Igbo-Ora (810.6 ± 309.0 versus 347.5 ± 153.1 mg; P < 0.001) and FGF23 levels correlated significantly with total urinary phosphate excretion (r = 0.62; P < 0.001) and urinary phosphate-to-creatinine ratios (r = 0.50; P < 0.001). Conclusions. Living in a more westernized society may be associated with greater net phosphate absorption, as reflected by higher urinary phosphate excretion, and higher FGF23 levels. [ABSTRACT FROM AUTHOR]

Background Phosphorus (P) supplementation is costly and can result in excess P excretion. This study investigated the effects of reducing dietary P on milk production and P excretion in dairy cows over a full lactation. Method Forty-five multiparous Holstein dairy cows were divided into 15 blocks according to expected calving date and previous milk yield, and assigned randomly to one of the three dietary treatments: 0.37, 0.47, and 0.57% P (DM basis); these P levels represent the NRC recommendations, Chinese recommendations, and the amount of dietary P commonly fed by Chinese dairy farmers, respectively. Average daily feed intake was calculated from monthly data on feed offered and refused. Milk yields of individual cows were recorded weekly, and milk samples were taken for analysis of protein, fat, solids-not-fat, lactose, and somatic cell count. Blood samples were collected on days -6, -3, 0, 3, 6 relative to calving, and then monthly throughout lactation, and analyzed for P and Ca concentrations. Spot samples of feces and urine were collected for 3 consecutive d during weeks 12, 24, and 36, and P concentrations were analyzed. Reproduction and health data were recorded. Results Dietary P did not affect dry matter intake or milk yield (P > 0.10). Milk fat content was slightly higher in cows fed 0.37% P than in cows fed 0.47% P (P = 0.05). Serum concentrations of P and Ca did not reflect dietary P content (P > 0.10). Fecal and urinary P both declined linearly (P < 0.05) as dietary P decreased from 0.57 to 0.37%. Fecal P content was 25% less when dietary P was 0.37% compared to 0.57%. Health events and reproductive performance were not associated with dietary P content (P > 0.05). Conclusions Lowering dietary P from 0.57 to 0.37% did not negatively affect milk production, but did significantly reduce P excretion into environment. [ABSTRACT FROM AUTHOR]

Dairy cow bone phosphorus (P) mobilization and deposition and their influence on P requirements were studied over the lactation cycle. Thirty Holsteins received a common diet during the dry period and one of the following three dietary treatments that varied in P percentage during the subsequent lactation (44 weeks): (i) 0.36 throughout (constant P, 0.36-0.36-0.36), (ii) 0.36 for 30 weeks then 0.29 for 14 weeks (P changed once, 0.36-0.36-0.29), and (iii) 0.43 for 10 weeks, 0.36 for 20 weeks, and 0.29 for 14 weeks (P changed twice, 0.43-0.36-0.29). Six P balance studies were conducted during the experiment, including one during the dry period and five along lactation, based on P intake, faecal P, urinary P and milk P, when appropriate. Blood samples were taken during balance to analyse bone formation (osteocalcin) and resorption (pyridinoline) marker concentrations and rib biopsies performed to determine bone P content. Phosphorus balance was negative during weeks −4 to −1 relative to lactation for all groups and remained negative for cows fed 0.36% P during weeks 1-5, but showed a positive value for cows that received 0.43% P. The balance was close to zero for all groups at weeks 19-23 and showed a clear retention during weeks 38-42; by the end of lactation, cows re-stored most of the P mobilized earlier. The pattern in P balance was consistent with changes in blood bone metabolism marker concentrations, rib bone P content, and faecal and urinary P concentrations over the experiment, indicating that cows, irrespective of the dietary P treatments received, mobilized P from bone during the late dry period when fed a low-Ca diet and early lactation, and re-stored P in late lactation. This dynamic of P metabolism can have important implications for dietary P requirements and ration formulations. [ABSTRACT FROM AUTHOR]

Phosphorus metabolism in laying hens is a highly dynamic process over the course of the 24 h egg-laying cycle. Adjusting the phosphorus feeding regimen according to the daily egg-laying cycle may help to improve phosphorus utilization efficiency. Hy-Line Brown layers ( n  = 120; 70 wk old) were offered 4 different phosphorus daily regimens: (1) RR, fed regular phosphorus at both 09:00 and 17:00; (2) RL, fed regular phosphorus at 09:00 and low phosphorus at 17:00; (3) LR, fed low phosphorus at 09:00 and regular phosphorus at 17:00; (4) LL, fed low phosphorus at both 09:00 and 17:00. The regular and low phosphorus diets contained 0.32% and 0.14% non-phytate phosphorus, respectively. The feeding trial lasted for 12 wk. As a result, layers on the RL regimen had decreased laying rate ( P  < 0.05; 5 to 8, 9 to 12, and 1 to 12 wk) when compared to all other regimens. Layers on the LL regimen had decreased eggshell thickness and specific gravity ( P  < 0.05; wk 8) when compared to all other regimens, and had decreased egg shell strength ( P  < 0.05; wk 8) when compared to RL and LR regimens. When compared to the RR regimen (a common practice in the industry), layers on the LR regimen had: (1) identical laying performance and egg quality ( P  > 0.05); (2) decreased phosphorus excretion ( P  < 0.05) during the period of 09:00 to 17:00; (3) increased jejunal calbindin D28k protein expression ( P  < 0.05) 2 h after feeding in the morning; (4) decreased serum fibroblast growth factor 23 and calcitriol levels ( P  < 0.05), decreased jejunal type III sodium-phosphate cotransporter 2 gene and protein expression ( P  < 0.05), and decreased renal type III sodium-phosphate cotransporter 1 protein expression ( P  < 0.05), 2 h after feeding in the afternoon. In summary, when dietary phosphorus was supplemented in accordance with daily serum phosphorus rhythms (i.e., the LR regimen), laying performance and egg quality were well supported whilst significantly decreasing phosphorus consumption and excretion. Thus, serum phosphorus rhythms will need to be carefully maintained when developing dietary phosphorus-reduction strategies in laying hens., Competing Interests: The authors declare that they have no competing interests., (© 2022 The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.)

Juvenile rainbow trout (Oncorhynchus mykiss) were fed diets in which fishmeal was totally replaced by mixtures of Spirulina powder and soybean meal. Three experimental diets were formulated with 75% Spirulina and 25% soybean meal, 50% Spirulina and 50% soybean meal, and 25% Spirulina and 75% soybean meal. A commercial diet and a diet with 100% fishmeal served as controls. Diets were fed to triplicate groups of 10 juveniles with an initial weight of 6.8±0.4 g for 50 days. At the end of the experiment, growth performance, oxygen consumption, nitrogen and phosphorus excretion, protein digestibility, and serum protein content and lysozyme activity were evaluated. Data were analyzed by one-way ANOVA. Growth performance was not significantly affected by the experimental diets, but values tended to be lower as the level of dietary soybean meal increased. Among the experimental diets, the 75% Spirulina/25% soybean diet produced the best growth performance. Further, in fish fed this diet, the apparent coefficient of digestibility of protein was higher than 98% (as with all diets), oxygen consumption was lower and lysozyme activity was higher than in fish fed other replacement diets, and dissolved phosphorus and phosphorus in feces were similar or lower than in the controls. The present research shows the possibility of using mixtures of Spirulina powder and soybean meal as total substitutes of fishmeal in diets for juvenile rainbow trout. [ABSTRACT FROM AUTHOR]

Energy metabolism and phosphorus excretion were studied in Littorina littorea and L. saxatilis snails from the White Sea. Some elemental components of the body were determined quantitatively, and the rates of oxygen consumption and phosphorus excretion were estimated. All parameters were calculated relative to dry body weight (mg). Daily expenditures for energy metabolism in Littorina spp. averaged 3.6 ± 1.1%, and those for phosphorus metabolism were approximately four times lower (about 1%), with the total phosphorus content averaging 0.8% dry body weight. The atomic ratio of consumed oxygen to excreted phosphorus for both species averaged O: P = 1164 ± 140. [ABSTRACT FROM AUTHOR]

The first aim of this study was to examine the effects of strain and age on phytate phosphorus (PP) utilization and intestinal phytase activity (IPA) in two strains of laying hens, Hyline Brown (HB) and Hy-line White W-36 (HW) at 32, 52 and 72 weeks of age. A digestion trial was conducted using the indicator method and birds were sampled to measure IPA. The second aim was to examine the effect of feed grade exogenous phytase enzyme on total (TP), water soluble (WSP) and phytate phosphorus (PP) excretion in the HW strain fed varying levels of phosphorus. Hens were fed three concentrations of available P (AP): 0.2, 0.3 and 0.4%. Each level of P was supplemented with three levels of commercial feed grade exogenous phytase enzyme (0, 300, and 600 FTU/kg) and the amount of TP, WSP and PP in excreta per 100 g of feed consumed was calculated. The HB retained more PP as compared to HW. Intestinal phytase activity showed a significant (P<0.01) age effect with the highest activity occurring at 32 weeks. There were significant differences in the amount of TP and SP excreted between birds receiving the 3 levels of phosphorus with 300 units phytase (P<0.01). The results of this study showed that layers are capable of utilizing PP, and that utilization is regulated by IPA and varies with age. Exogenous phytase improved PP utilization but it increased the amount of TP and WSP in excreta. [ABSTRACT FROM AUTHOR]

The aim of this study was to establish age appropriate reference intervals for calcium (Ca), phosphorus (P) and total protein (UTP) in random urine samples. All analytes were measured using the Roche MODULAR P analyzer and normalized to creatinine (Cr). Our study cohort consisted of 674 boys and 728 girls between 7 and 17 years old (y.o.), which allowed us to determine the central 95% reference intervals with 90% confidence intervals by non-parametric analysis partitioned by both gender and 2-year age intervals for each analyte [i.e. boys in age group 7–9 years (7–9 boys); girls in age group 7–9 years (7–9 girls), etc.]. Results for the upper limits of the central 95% reference interval were: for Ca/Cr, 0.27 (16,17 y.o.) to 0.46 mg/mg (7–9 y.o.) for the girls and 0.26 (16,17 y.o.) to 0.43 mg/mg (7–9 y.o.) for the boys; for P/Cr, 0.85 (16,17 y.o.) to 1.44 mg/mg (7–9 y.o.) for the girls and 0.87 (16,17 y.o.) to 1.68 mg/mg (7–9 y.o.) for the boys; for UTP/Cr, 0.30 (7–9 y.o.) to 0.34 mg/mg (10–12 y.o.) for the girls and 0.19 (16,17, y.o.) to 0.26 mg/mg (13–15 y.o.) for the boys. Upper reference limits decreased with increasing age, and age was a statistically significant variable for all analytes. Eight separate age- and gender-specific reference intervals are proposed per analyte. [ABSTRACT FROM AUTHOR]

The physiological activity of grazers related to feeding, assimilation, and excretion may either increase or decrease the productivity of algae in a periphyton community, depending on the size of the consumer and its population density. Population data on the numbers and biomass of Anisus spp. have been used to calculate the amount of mineral phosphorus per unit area regenerated in the medium through animal metabolism. No difference in the rate of soluble reactive phosphorus (SRP) excretion has been found between pulmonates and the bivalve Sphaerium suecicum. [ABSTRACT FROM AUTHOR]

The importance of animals for mediating ecosystem processes has long been recognized by ecologists. Traditionally, consumer‐mediated dynamics have been considered through consumptive pathways such as predation and herbivory. Yet, consumers also play critical roles in mediating "bottom‐up" pathways associated with nutrient dynamics. Foundational research demonstrated the importance of these dynamics in terrestrial, freshwater, and pelagic marine ecosystems, and introduced novel perspectives on the role of animals such as wildebeest, lacustrine fishes, and zooplankton, respectively, for providing an important source of nutrients that limit primary production. This research inspired a substantial body of research on the importance of consumer‐mediated nutrient dynamics for ecosystem function. Despite this, only recently have ecologists begun to extend this line of thinking toward coastal marine ecosystems. The data presented herein is a comprehensive study of consumer nutrient dynamics from invertebrates and fishes that live in subtropical and tropical Caribbean coastal marine waters, including mangroves, seagrass beds, and coral reefs. This data set represents the largest, to my knowledge, published nutrient stoichiometry data set from a single system, including estimates of excretion rates (n = 900 individuals total; n = 667 individual fish, size range 0.14–2,597 g [2–107 cm]; n = 233 invertebrates, size range 0.04–487 g), and somatic nutrient content analyses (n = 658 individuals total, n = 494 vertebrates, n = 164 invertebrates). These data also include δ13C and δ15N stable isotopes of whole body, body mass (wet mass), taxonomic identification to class‐level, and functional group classification. These data have been used to test basic ecological theory, to scale individual‐level processes to coral reef, mangrove, and seagrass ecosystems, and to understand the role of human impacts for mitigating consumer‐mediated nutrient dynamics. While these findings have helped improve our understanding of nutrient dynamics in tropical coastal ecosystems, these data offer a wealth of additional promise for advancing ecological theory and applied science in tropical marine ecosystems and beyond. Users are free to use and analyze the data. Attribution should be given to this presentation of the data. [ABSTRACT FROM AUTHOR]

Two experiments were completed to determine the potential for using distillers dried grains with solubles (DDGS) in diets with or without phytase to provide available P, energy, and protein to highly productive lactating sows without increasing their fecal P. In Exp. 1, the dietary treatments were as follows: (1) corn and soybean meal with 5% beet pulp (BP) or (2) corn and soybean meal with 15% DDGS (DDGS). Besides containing similar amounts of fiber, diets were isonitrogenous (21% CP, 1.2% Lys) and isophosphorus (0.8% P). Sixty-one sows were allotted to dietary treatments at approximately 110 d of gestation (when they were placed in farrowing crates) based on genetics, parity, and date of farrowing. Sows were gradually transitioned to their lactation diet. On d 2 of lactation, litters were cross-fostered to achieve 11 pigs/litter. Sows and litters were weighed on d 2 and 18. Fecal grab samples were collected on d 7, 14, and 18 of lactation. Dietary treatment did not affect the number of pigs weaned (10.9 vs. 10.8) or litter weaning weight. On d 14, DDGS sows had less fecal P concentration than BP sows (28.3 vs. 32.8 mg/g; P = 0.04). Fecal Ca of sows fed DDGS decreased for d 7, 14, and 18 (55.6, 51.4, and 47.1 mg/g of DM, respectively; P = 0.05) but not for BP sows. In Exp. 2, the dietary treatments were as follows: (1) corn and soybean meal (CON), (2) CON + 500 phytase units of Natuphos/kg diet, as fed (CON + PHY), (3) corn and soybean meal with 15% DDGS and no phytase (DDGS), or (4) DDGS + 500 FTU of Natuphos/kg of diet, as fed (DDGS + PHY). Sows (n = 87) were managed as described for Exp 1. Litter BW gain (46.0, 46.3, 42.1, and 42.2 kg; P = 0.25) and sow BW loss (8.1, 7.2, 7.4, and 6.3 kg for CON, CON + PHY, DDGS, and DDGS + PHY, respectively; P = 0.97) were not affected by dietary treatment. Fecal P concentration did not differ among dietary treatments but was reduced at d 14 and 18 compared with d 7 (P = 0.001). However, fecal phytate P concentration was decreased by the addition of DDGS when DDGS and DDGS + PHY were compared with the CON sows except on d 7 (P < 0.05). Sows fed CON diet had greater fecal phytate P than sows fed DDGS, and sows fed DDGS + PHY had less fecal phytate P than sows fed DDGS with no phytase (P = 0.001). Although these experiments were only carried out for 1 lactation, these results indicate that highly productive sows can sustain lactation performance with reduced fecal phytate P when fed DDGS and phytase in lactation diets. [ABSTRACT FROM AUTHOR]

This review summarizes the environmentally friendly methods that are available to manage phosphorus (P) excretion. Phase feeding reduces P excretion up to 10–25% by adding precise amounts of P to broiler diets. Increasing of the Ca:P ratio in diets from 1: 1 to 2: 1 decreased the availability of P from phytic acid. Feeding diets supplemented with vitamin D can increase phytin P (PP) utilization from 31–50 to 68–87%. Total P (TP) excretion by poultry may be reduced by up to 50% through the use of supplemental phytase. Reductions in phytic acid P ranging from 50 to 65% with no decreases in TP of the seed were seen in ‘low-phytic acid’ or ‘high-available P’ (HAP) mutants when phytase supplementation was contained in diet. However, total activity of phytase was 35% higher in the small intestine of laying hens because of different pH. And both microbial phytase and lactic acid enhanced the apparent total tract digestibility (ATTD) of ash, Ca and Mg and apparent ileal digestibility (AID) of phytic acid. [ABSTRACT FROM PUBLISHER]

Abstract: A feeding experiment was conducted to investigate the effects of exogenous enzymes (phytase, non-starch polysaccharide enzymes: WX and VP, supplied by DSM) on growth performance and excretion of Japanese seabass (Lateolabrax japonicus) (initial mass 6.26±0.10 g). A basal diet was used as a control that contained a mixed protein source, and lysine, methionine and valine were supplemented to simulate the essential amino acid pattern of fish meal. Four other diets were supplemented with 200 mg phytase (500 IU), 400 mg VP, 800 mg WX, or a combination of 800 mg WX and 400 mg VP per kg diet, respectively. Each diet was assigned to triplicate groups of fish in floating sea cages, and each cage was stocked with 60 fish. The results showed specific growth rate (SGR) and feed efficiency ratio (FER) were not significantly improved by the phytase supplementation. However, supplementations with WX and VP significantly enhanced the SGR and FER (P <0.05). Phosphorus retention was significantly increased by the supplementation with phytase, whereas nitrogen retention was also enhanced by supplementations of non-starch polysaccharide enzymes (P <0.05). The excretion experiment showed that the soluble phosphorus and ammonia nitrogen in starved fish were constant, irrespective of dietary treatments. The total phosphorus effluent in fish fed the diet with phytase supplementation was significantly lower compared with the control group after feeding to satiation (P <0.05), but soluble phosphorus excretion was still independent of dietary treatments. The ammonia excretion in satiated fish significantly decreased with supplementations of non-starch polysaccharide enzymes. [Copyright &y& Elsevier]

Abstract: Excess phosphorus (P) in aquaculture feeds contributes to the eutrophication of natural waters. While commercially available low-P (LP) fish feeds have been developed, there is uncertainty about their potential to reduce effluent P while maintaining fish growth relative to regular P (RP) feeds. We therefore simulated commercial aquaculture conditions and fed for 55days rainbow trout (∼190kg/raceway, n =3 raceways/diet) RP (1.4% total P) and LP (1.0%) feeds then determined effluent P levels, fish growth, and feed costs. Excretions of fecal-P and soluble-P, but not particulate-P, in effluents were greater in RP than in LP ponds. Fish growth, bone-P and plasma-P were similar between diets, demonstrating that LP feeds can lower effluent P levels without compromising growth. Costs were $0.97/kg fish production for LP feeds, and $0.74/kg for RP. Because feed is the largest variable cost in commercial aquaculture, the use of LP feeds can significantly increase production costs. [Copyright &y& Elsevier]

Abstract: In this study, the effects of reducing the dietary phosphorus (P) supply during the first 4 months of lactation on P balance and bone metabolism were investigated in dairy cows during a full lactation, including the dry period. Twenty-two multiparous cows of the Swedish Red and White Breed were included in the experiment. Eleven cows received a dietary P concentration of 0.43% of DM during the whole lactation (NP), and 11 cows received a dietary P concentration of 0.32% of DM during the first 4 months of lactation, followed by 0.43% of DM during the rest of lactation (LP). Total collection of faeces was carried out during five different stages of lactation, for 5 consecutive days at each occasion. The dynamics of bone metabolism was investigated by monitoring one bone-formation marker, identifying osteocalcin (OC), and one bone-resorption marker identifying C-telopeptide fragments of collagen type I (CTx) in blood plasma. At the two first collection periods, 3–7 and 11–15 weeks after parturition, the apparent digestibility of P was higher in the LP cows (52%) than in the NP cows (42%). During the following collection periods, no difference in the apparent digestibility could be noted between the two groups of cows. Phosphorus retention did not differ between treatments at any collection period. The highest retention was observed during late lactation and during the dry period. The profiles of the bone metabolism markers indicated a net resorption of bone during early lactation, but there were no differences in marker concentrations between the groups during early lactation, indicating that the LP diet did not induce a further elevated net bone resorption. [Copyright &y& Elsevier]

Abstract: Phosphorus excretion in faeces was measured by total collection using dairy cows fed five amounts of P in a 5×5 Latin square design with three week periods. Milk production was 23±4 kg per day at the onset of the trial (DIM 185±11). Different quantities of monosodium phosphate (MSP) were added to a basal diet to obtain daily P intake levels of 44, 67, 92, 117 and 142 g (2.4, 3.7, 5.1, 6.4 and 7.8 g P kg− 1of DM, respectively). Faecal P excretion increased linearly (r 2 =0.97) as dietary P intake increased and the apparent digestibility of P was calculated to be 0.37, 0.28, 0.22, 0.21 and 0.22, respectively. The relatively low apparent digestibility is explained by excess P intake in relation to the requirements. The concentration of P in faeces ranged from 4 to 23 g kg− 1 of DM corresponding to the lowest and highest level of P intake, respectively. Variation of P in faecal output was substantial among days, though total DM and P intake was constant throughout the collection periods. Results indicate a requirement for sampling over at least 5 consecutive days, even when using total faecal collection. [Copyright &y& Elsevier]

This study was undertaken to determine the effect of dietary P content and fiber source on P utilization. Four dietary treatments were formed in a 2 x 2 factorial arrangement. The P content was 0.32 or 0.44%, and the fiber source was varied by substituting 10% soyhulls for 6% alfalfa hay on a dry matter (DM) basis. Diets also contained approximately 50% corn silage and alfalfa silage for all treatments. The diets were fed to 32 early to midlactation Holsteins for 10 wk. Fecal P excretion was estimated using indigestible acid detergent fiber marker determined with 12-d in situ incubation and grab sampling. Milk yield was high, averaging 43 kg/ d across treatments, and 42.1 and 44.0 kg/d for the 0.32 and 0.44% P diets, respectively. Milk fat content was also high, averaging 3.68 and 4.12% for the 0.32 and 0.44% P diets, respectively. Milk protein yield averaged 1.240 and 1.323 kg/d. Differences in milk production were associated with 1.5 kg/d less DM intake for the lower P diets on average. Based on lactation performance, 0.32% P appeared inadequate for this level of production, whereas the calculated (National Research Council) requirement was 0.37%. Fecal P concentration increased linearly with P intake, and based on this relationship, reducing dietary P from 0.44 to 0.37% would reduce fecal P excretion by 12%. Partial substitution of soyhulls for alfalfa hay did not affect feed intake or milk production, but reduced fecal P excretion, partially because of increased P apparent digestibility. The reduction in fecal P excretion resulting from reduced P intake or substitution of soyhulls for alfalfa hay was apparently through reductions in the regulated portion of fecal P. Cows producing 43 kg/d of milk appeared to need >0.32% P, whereas the requirement assessed from National Research Council data was 0.37%. Using highly digestible nonforage fiber sources in place of forage fiber sources in the diet may allow less P to be fed while still meeting the requirement. [ABSTRACT FROM AUTHOR]

Thirty-four Holstein dry cows and 16 lactating cows were used in balance trials to identify the effects of feeding and animal performance on nitrogen (N), phosphorus (P) and potassium (K) excretion by dairy cows, and to develop prediction models for these excreta. Orchard grass silage, corn silage, alfalfa silage or timothy hay were offered to dry cows. Orchard grass silage or alfalfa silage, and concentrates were offered to lactating cows. In the statistical analysis, the independent variables were bodyweight (kg), dry matter (DM) intake (kg/day), milk yield (for lactating cows only, kg/day), water intake (free water plus water in feed, kg/day), intake (g/day) of N, P and K and dietary contents (% of DM) of crude protein, P and K. The dependent variables were N, P and K excretion (g/day) in feces and urine. In both dry and lactating cows, intake of N, P and K had large effects on corresponding excretion. The results indicated that a decrease in the intake of N, P and K could decrease the corresponding excretion. Further research by path analysis showed that K intake positively affected urinary N excretion in dry cows indirectly, through water intake and urine volume. [ABSTRACT FROM AUTHOR]