Commercial application of polychaete sand filters for wastewater remediation and broodstock feeds

Summary Prototype sand-worm filtration beds were constructed at two prawn farms and one fish farm to assess and demonstrate their polychaete (marine worm) production and wastewater remediation capacities at semi-commercial scale. Wastewater treatment properties were monitored and worms produced were assessed and either sold for bait or used by the farms’ hatcheries as broodstock (prawn or fish breeder) feed. More than 34 megalitres of prawn- and fish-pond water was beneficially treated in the 116-319-d trial. The design of the polychaete-assisted sand filters (PASFs) constructed at each farm affected their water handling rates, which on average ranged from 315 to 1000 L m-2 d-1 at the three farms. A low profile design incorporating shallow bunded ponds made from polyethylene liner and timber stakes provided the easiest method of construction. This simple design applied at broad scale facilitated the highest quantities of treated water and the greatest worm production. Designs with higher sides increased the head pressure above the sand bed surface, thus increasing the amount of water that could be treated each day. Most water qualities were affected in a similar way to that demonstrated in the previous tank trials: dissolved oxygen, pH, total suspended solids and chlorophyll a levels were all consistently significantly lowered as pond water percolated through the sand bed, and dissolved forms of nitrogen and phosphorus were marginally increased on several occasions. However, unlike the previous smaller-scale tank trials, total nitrogen (TN) and total phosphorus (TP) levels were both significantly lowered by these larger-scale PASFs. The reasons for this are still unclear and require further research. Maximum TN and TP removals detected in the trial were 48.8% and 67.5%, respectively, and average removals (in unfed beds) at the three farms ranged from 20.0 to 27.7% for TN and from 22.8 to 40.8% for TP. Collectively, these results demonstrate the best suspended solids, chlorophyll and macronutrient removal capacities so far reported for any mariculture wastewater treatment methodology to date. Supplemental feeding of PASFs with fish meal was also investigated at one farm as a potential means of increasing their polychaete biomass production. Whilst fed beds produced higher biomass (152 ± 35 g m-2) compared with unfed beds (89 ± 17 g m-2) after 3.7 months of operation, the low number of replicates (2) prevented statistically significant differences from being demonstrated for either growth or survival. At harvest several months later, worm biomass production was estimated to be similar to, or in slight excess of, previously reported production levels (300-400 g m-2). Several qualities of filtered water appear to have been affected by supplemental feeding: it appeared to marginally lower dissolved oxygen and pH levels, and increased the TN and TP levels though not so much to eliminate significant beneficial water treatment effects. Periodic sampling during an artificial-tide demonstrated the tendency for treated-water quality changes during the first hour of filtration. Total nitrogen and ammonia peaked early in the tidal flow and then fell to more stable levels for the remainder of the filtration period. Other dissolved nutrients also showed signs of this sand-bed-flushing pattern, and dissolved oxygen tended to climb during the first hour and become more stable thereafter. These patterns suggest that the routine sampling of treated water undertaken at mid-inflow during the majority of the wider study would likely have overestimated the levels of TN and dissolved nutrients discharged from the beds, and hence underestimated the PASFs treatment efficacies in this regard. Analyses of polychaete biomass collected from each bed in the study revealed that the worms were free from contamination with the main prawn viruses that would create concerns for their feeding to commercial prawn broodstock in Australia. Their documented proximal and nutritional contents also provide a guide for hatchery operators when using live or frozen stock. Their dry matter content ranged from 18.3 to 22.3%, ash ranged from 10.2 to 14.0%, gross energy from 20.2 to 21.5 MJ kg-1, and fat from 5.0 to 9.2%. Their cholesterol levels ranged from 0.86 to 1.03% of dry matter, whilst total phospholipids range from 0.41 to 0.72%. Thirty-one different fatty acids were present at detectable (≥0.005% of dry matter) levels in the sampled worm biomass. Palmitic acid was by far the most prevalent fatty acid detected (1.21 ± 0.18%), followed by eicosapentaenoic (EPA) (0.48 ± 0.03%), stearic (0.46 ± 0.04%), vaccenic (0.38 ± 0.05%), adrenic (0.35 ± 0.02%), docosadienoic (0.28 ± 0.02%), arachidonic (AA) (0.22 ± 0.01%), palmitoleic (0.20 ± 0.04%) and 23 other fatty acids with average contents of less than 0.2% of dry matter. Supplemental feeding with fish meal at one farm appeared to increase the docosahexaenoic acid (DHA) content of the worms considerably, and modify the average AA : EPA : DHA from 1.0 : 2.7 : 0.3 to 1.0 : 2.0 : 1.1. Consistent with previous results, the three most heavily represented amino acids in the dry matter of sampled worms were glutamic acid (8.5 ± 0.2%), aspartic acid (5.5 ± 0.1%) and glycine (4.9 ± 0.5%). These biomass content results suggest that worms produced in PASF systems are well suited to feeding to prawn and fish broodstock, and provide further strong evidence of the potential to modify their contents for specific nutritional uses. The falling wild-fishery production of marine bloodworms in Queensland is typical of diminishing polychaete resources world-wide and demonstrates the need to develop sustainable production methods here and overseas. PASF systems offer the dual benefits of wastewater treatment for environmental management and increased productivity through a valuable secondary crop grown exclusively on waste nutrients.

High-pressure NMR investigations of the protonic conductor (NH4)4Fe(CN)6.1.5H2O

The effect of high hydrostatic pressure up to 1.5 GPa on ionic motion in (NH4)4Fe(CN)6.1.5H2O has been studied by wide-line 1H NMR experiments performed in the temperature range from room temperature to 77 K. The experiments at room temperature have shown a large increase in the second moment at 0.45 GPa as a result of a pressure-induced phase transition. The temperature dependence study up to 0.425 GPa has shown a gradual increase in the values of activation energy and attempt frequency with increase in pressure. The activation volume for motion at 300 K has been estimated to be 6% of molar volume. Vacancy-assisted ionic jumps are concluded to be the mode of charge transport. Second moments estimated at 77 K show evidence for tunnelling reorientation of at least one of the two NH4+ groups in the compound.

The effect of multisubstitution on the thermoelectric properties of chalcogenide-based Cu2.1Zn0.9Sn1-xInxSe4 (0 <= x <= 0.1)

Quinary chalcogenide compounds Cu2.1Zn0.9Sn1-xInxSe4 (0 <= x <= 0.1) were prepared by melting (1170K) followed by annealing (773 K) for 172 h. Powder X-ray diffraction (XRD) data accompanied by electron probe microanalysis (EPMA) and Raman spectra of all the samples confirmed the formation of a tetragonal kesterite structure with Cu2FeSnS4-type. The thermoelectric properties of all the samples were measured as a function of temperature in the range of 300-780K. The electrical resistivity of all the samples exhibits metallic-like behavior. The positive values of the Seebeck coefficient and the Hall coefficient reveal that holes are the majority charge carriers. The codoping of copper and indium leads to a significant increase of the electrical resistivity and the Seebeck coefficient as a function of temperature above 650 K. The thermal conductivity of all the samples decreases with increasing temperature. Lattice thermal conductivity is not significantly modified as the doping content may infer negligible mass fluctuation scattering for copper/zinc and indium/tin substitution. Even though, the power factors (S-2/rho) of indium-doped samples Cu2.1Zn0.9Sn1-xInxSe4 (x = 0.05, 0.075) are almost the same, the maximum zT = 0.45 at 773K was obtained for Cu2.1Zn0.9Sn0.925In0.075Se4 due to its smaller value of thermal conductivity. (C) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The relationship between some physicochemical parameters and plankton composition on fish production in ponds

The effect of physico-chemical parameters and plankton composition on fish production in ponds was investigated in six fish farms for eight weeks. The physicochemical parameters investigated were temperature=25-30 plus or minus C, transparency=0.45-0.57m, dissolved oxygen=3.0-10.9mg/l, pH=6.0-7.7, dissolved carbon dioxide=5.46-28.3mg/l, total alkalinity=44.37-80.0ppm, chemical oxygen demand=31.88-72.18mg/l and biological oxygen demand=0.66-48.34mg/l. Plankton composition varies and was made of four families of phytoplankton namely; Cyanophyceae, Chlorophyceae, Dinophyceae and Diatomida; and four families of zooplankton viz; Protozoa, Rotifera, Copepoda and Dinoflagellates. Farm 1 and 6 recorded the highest average weight of about 1.0kg and average total length of about 40.0cm for the two fish species. This study showed that fish yield was dependable on the quality and management of pond water characteristics

The relationship between some physicochemical parameters and plankton composition on fish production in ponds

The effect of physico-chemical parameters and plankton composition on fish production in ponds was investigated in six fish farms for eight weeks. The physicochemical parameters investigated were temperature=25-30 plus or minus C, transparency=0.45-0.57m, dissolved oxygen=3.0-10.9mg/l, pH=6.0-7.7, dissolved carbon dioxide=5.46-28.3mg/l, total alkalinity=44.37-80.0ppm, chemical oxygen demand=31.88-72.18mg/l and biological oxygen demand=0.66-48.34mg/l. Plankton composition varies and was made of four families of phytoplankton namely: Cyanophyceae, Chlorophyceae, Dinophyceae and Diatomida; and four families of zooplankton viz: Protozoa, Rotifera, Copepoda and Dinoflagellates. Farm 1 and 6 recorded the highest average weight of about 1.0kg and average total length of about 40.0cm for the two fish species. This study showed that fish yield was dependable on the quality and management of pond water characteristics

Superfluid nuclear matter in BCS theory and beyond

Medium polarization effects are studied for S-1(0) pairing in nuclear matter within BHF approach. The screening potential is calculated in the RPA limit, suitably renormalized to cure the low density mechanical instability of nuclear matter. The self-energy corrections are consistently included resulting in a strong depletion of the Fermi surface. The self-energy effects always lead to a quenching of the gap, whereas it is almost completely compensated by the anti-screening effect in nuclear matter.

Dependence of superconducting temperature on chemical bond parameters in YBa2Cu3O6+delta (delta=0-1)

The chemical bond parameters, that is ionicities and average energy gaps, for all types of chemical bonds in YBa2Cu3O6+delta have been investigated with variation of oxygen content delta (delta = 0.0, 0.35, 0.45, 0.58, 0.64, 0.73, 0.78, 0.81, 0.95, 1.00). The theory used is the complex crystal chemical bond theory, which is the development of P-V-L theory. The two plateaus near 90 K and 60 K in superconducting transition temperatures, and the disappearance of superconductivity with the change of oxygen content, were reasonably explained by chemical bond parameters. The results also showed that the Cu-O chains play a vital role in the transition from non-superconductors to superconductors, and the highest transition temperature occurred when the plane-chain reached a coupling state. (C) 1998 Elsevier Science Ltd. All rights reserved.

Electrochemical behavior of the molybdotungstate heteropoly complex with neodymium, K10H3[Nd(SiMo7W4O39)(2)]center dot xH(2)O in aqueous solution

The electrochemical behavior of the title compound (denoted Nd(SiMo7W4)(2)(13-)) in aqueous solution has been studied using cyclic voltammetry, sampled d.c. voltammetry, differential pulse voltammetry and bulk electrolysis with coulometry, The stable pH range of Nd(SiMo7W4)(2)(13-) is determined with UV-visible spectra. In the potential range between 0.70 and -0.45 V vs. SCE, the anion in pH 3.8 aqueous solution undergoes one-, one-, two- and two-electron steps of four redox processes attributed to electron addition and removal from the molybdate-oxo framework. The adsorption of the anion on the dropping mercury electrode and a self-inhibition influence of the adsorbed anions on the redox process of those anions dissolved in solution are found. The unusual dependence of the formal potentials on pH is explained with the competition of the protonation and ion-pair formation due to the high negative charge of Nd(SiMo7W4)(2)(13-) and its reduced forms. The electrocatalytic effects of the anion on the bromate are investigated.

中国北方草本植物及表土有机质碳同位素组成

Recently, more and more attention has been paid to stable isotope ratios in terrestrial depositional systems. Among them, δ~(13)C value is mainly determined by the surface vegetation, while vegetation is directly related to climate, therefore, carbon isotope ratio in soil organic matter and pedogenic carbonate has been employed as an important paleoecological indicator. In order to test the paleoecological information extracted from stable isotope ratios in terrestrial depositional systems, it is necessary to study the relationships between δ~(13)C value in standing terrestrial plants and today climate, as well as between δ~(13)C value in modern surface soil organic matter and standing vegetation. Thus, these relationships were studied in this paper by means of analysing δ~(13)C in standing plants and modem surface soil organic matter in North China. The main results and conclusions are presented as following: 1. According to their δ~(13)C values, 40 C-4 species represent about 16% of the 257 plant species sarnpled from the North China. C-4 photosynthesis mainly occurs in Poaceae, Cyperaceae and Chenopidaceae families, and percentage representation of C-4 photosynthesis is up to 56% in Poaceae family. 2. The δ~(13)C values of C-3 plant species in North China vary from -21.7‰ to -32.0‰ with an average of -27.1‰, and 93% focus on the range of -24.0‰ ～ -30.0‰; δ~(13)C values of C-4 plant species in North China are between -10.0‰ ～ -15.5‰ with an average of -12.9‰, and 90% concentrate on the range of -11.0‰ ～ -15.0‰. 3. The δ~(13)C composition of C-3 plant species collected from Beijing, a semi-moist district, mainly vary between -27.0‰ ～ -30.0‰, and the average is -28.7‰; the δ ~(13)C values of plants in the semi-arid district, east and west to the Liu Pan Moutain, focus on the range of-26.0‰ ～ -29.0‰ and -25.0‰ ～ -28.0‰, respectively, with the mean value of -27.6‰ and -26.6‰, respectively; the δ~(13)C composition in the arid district dominantly vary from -24.0‰ to -29.0‰, with the average of -26.2‰, and among them, the δ~(13)C values of C-3 plant species in deserts are often between - 22‰ ～ -24‰; the δ~(13)C values in the cold mountain district concentrate on the range of -24.0‰ to -29.0‰, with the average of -26.3‰. 4. The main range of δ~(13)C composition of C-4 plant species, derived from Beijing, a semi-moist district, are -13.0‰ ～ -15.5‰; the semi-arid district, -11.0‰ ～ -14.0‰; the arid district, -11.0‰ ～ -14.0‰. The mean values of them are -14.0‰, -12.4‰,-12.7‰, respectively. 5. From east to west in North China, δ~(13)C values of C-3 plant species increase with longitude. The correlation between δ~(13)C ratios of C-3 plant species and longitude is linear. Changing temperate and precipitation and changing atmosphere pressure are spossible explanations. 6. Almost all C-3 plant species have the trends that their δ~(13)C values gradually increase with decreasing precipitation, decreasing temperature and increasing altitude. Our results show the increases of the δ~(13)C value by 0.30 ～ 0.45‰, 0.19 ～ 0.27‰ and 1.1 ～ 1.2‰ per 100 mm, I℃ and 1000 m, respectively, for all C-3 plant species together. 7. The δ~(13)C values of all C-3 plant species together and a part of C-3 species show highly significant linear correlation with the mean annual temperature, the mean annual precipitation and the altitude, and the results suggest that they can be used as proxies of these environmental variables, while, those without highly significant correlation, may be not suitable as the proxies. 8. The extent, which of responses of δ~(13)C composition to environmental variables, is different for each C-3 plant specie. 9. The δ~(13)C variations along altitude and longitude may be non-linear for C-4 p1ant species in North China. The mean annual temperature may be not important influential factor, thus, it suggests that the δ~(13)C composition of C-4 plant species may be not suitable as the proxy of the mean annual temperature. The influences of summer temperature on δ~(13)C values are much bigger than that of annual temperature, among them, the influence of September temperature is biggest. The mean annual precipitation may be one of the dominant influential factors, and it shows a highly significant non-linear relationship with δ~(13)C values, and the result indicates that δ~(13) C composition of C-4 plant species can be employed as the proxy of the mean annual precipitation. 10. The variations of δ~(13)C ratios do not show systematic trends along longitude, latitude and altitude for modern surface soil organic in Northwest China. ll. The δ~(13)C ratios of modern surface soil organic do not exhibit systematic patterns with temperature and precipitation in Northwest China, it suggests that, unless soil organic is transferred from pure C-3 or C-4 vegetation, the δ~(13)C composition of soil organic may be not used as proxies of climatic variables. 12. The δ~(13)C values of modem surface soil organic are heavier than that of standing vegetation, and the difference ofrnean δ~(13)C between them is -2.18‰. 13. Without considering the δ~(13)C difference between vegetation and soil organic, as well as the δ~(13)C drift in various enviromnent, we may not obtain the valuable information of C-3, C-4 relative biomass in vegetation. 14. The C-4 biomass contribution in vegetation increase with decreasing latitude, increasing longitude and decreasing altitude in Northwest China. The C-4 biomass almost are zero in those regions north to 38 ° N, or west to 100°E, or above 2400 m. 15. The C-4 relative biomass in vegetation increase with growing temperature and precipitation. and, C-4 plants are rare at those regions where the mean annual temperature is less 4 ℃, or the mean annual precipitation is less 200 mm, and their biomass contribution in vegetation are almost zero. Both the mean annual temperature and the mean annual average precipitation may be the important influential factors of C-4 distribution, but the dominant factors.

Theoretical analysis on microwave heating of oil–water emulsions supported on ceramic, metallic or composite plates

A detailed theoretical analysis has been carried out to study efficient heating due to microwaves for one-dimensional (1D) oil–water emulsion samples placed on various ceramic, metallic (reflective) and ceramic–metallic composite supports. Two typical emulsion systems are considered such as oil-in-water (o/w) and water-in-oil (w/o). A preliminary study has been carried out via average power vs emulsion thickness diagram to estimate microwave power absorption within emulsion samples for various cases. The maxima in average power, also termed as ‘resonances’, are observed for specific emulsion thicknesses and the two consecutive resonances of significant magnitudes are termed as R1 and R2 modes. For both o/w and w/o emulsions, it is observed that microwave power absorption is enhanced in presence of metallic and composite supports during both R1 and R2 modes. The efficient heating strategies characterized by ‘large heating rates’ with ‘minimal thermal runaway’ i.e. uniform temperature distributions within the sample have been assessed for each type of emulsion. Based on the detailed spatial distributions of power and temperature for various cases, SiC-metallic composite support may be recommended as an optimal heating strategy for o/w samples with higher oil fractions (0.45) whereas metallic and Alumina-metallic composite supports may be favored for samples with smaller oil fractions (=0.3) during R1 mode. For w/o samples, SiC-metallic composite support may be suitable heating strategy for all ranges of water fractions during R1 mode. During R2 mode, metallic and Alumina-metallic composite supports are favored for both o/w and w/o emulsion samples. Current study recommends the efficient way to use microwaves in a single mode waveguide and the heating strategy can be suitably extended for heating of any other emulsions for which dielectric properties are easily measurable or available in the literature.

Factors influencing the activity of taurolidine against spores of Bacillus subtilis (NCTC 10073)

The cidal activities of aqueous taurolidine (2.0% w/v containing 5.0% wlv polyvinylpyrrolidone as a solubilising agent) and alcoholic taurolidine (2.0% w/v dissolved in Isopropyl alcohol 50% v/v) against spores of Bacillus subtilis NCTC 10073 were evaluated at 20 degrees C, 37 degrees C, 45 degrees C and 55 degrees C. Increased temperature increased both the rate and extent of sporicidal activity of both solutions. Total spore kill was not observed in either solution type over the range of temperatures and contact times examined. There were no observed differences between the sporicidal activities of aqueous and alcoholic taurolidine solutions at all temperatures examined. Ultrasonic energy (50 Hz operating frequency in a 150 W ultrasonic bath in conjunction with increasing temperature allowed to rise naturally from ambient temperature to 41 degrees C over 4 h) enhanced the sporicidal activities of both solution types. However, the difference in activity between the two solution types was not significant. Compared to normal spores, alteration of spore coat layers (hydrogen-form spores) did not alter spore susceptibility to aqueous taurolidine at elevated temperatures of 37 degrees C and 55 degrees C.

Compartmentalized Cerebral Metabolism of [1,6-(13)C]Glucose Determined by in vivo (13)C NMR Spectroscopy at 14.1 T.

Cerebral metabolism is compartmentalized between neurons and glia. Although glial glycolysis is thought to largely sustain the energetic requirements of neurotransmission while oxidative metabolism takes place mainly in neurons, this hypothesis is matter of debate. The compartmentalization of cerebral metabolic fluxes can be determined by (13)C nuclear magnetic resonance (NMR) spectroscopy upon infusion of (13)C-enriched compounds, especially glucose. Rats under light α-chloralose anesthesia were infused with [1,6-(13)C]glucose and (13)C enrichment in the brain metabolites was measured by (13)C NMR spectroscopy with high sensitivity and spectral resolution at 14.1 T. This allowed determining (13)C enrichment curves of amino acid carbons with high reproducibility and to reliably estimate cerebral metabolic fluxes (mean error of 8%). We further found that TCA cycle intermediates are not required for flux determination in mathematical models of brain metabolism. Neuronal tricarboxylic acid cycle rate (V(TCA)) and neurotransmission rate (V(NT)) were 0.45 ± 0.01 and 0.11 ± 0.01 μmol/g/min, respectively. Glial V(TCA) was found to be 38 ± 3% of total cerebral oxidative metabolism, accounting for more than half of neuronal oxidative metabolism. Furthermore, glial anaplerotic pyruvate carboxylation rate (V(PC)) was 0.069 ± 0.004 μmol/g/min, i.e., 25 ± 1% of the glial TCA cycle rate. These results support a role of glial cells as active partners of neurons during synaptic transmission beyond glycolytic metabolism.

Selenium supplementation of lactating dairy cows: effects on milk production and total selenium content and speciation in blood, milk and cheese

Forty-multiparous Holstein cows were used in a 16-wk continuous design study to determine the effects of either selenium (Se) source, selenized yeast (SY) (derived from a specific strain of Saccharomyces cerevisiae CNCM I-3060 Sel-Plex®) or sodium selenite (SS), or inclusion rate of SY on Se concentration and speciation in blood, milk and cheese. Cows received ad libitum a TMR with 1:1 forage:concentrate ratio on a dry matter (DM) basis. There were four diets (T1-T4) which differed only in either source or dose of Se additive. Estimated total dietary Se for T1 (no supplement), T2 (SS), T3 (SY) and T4 (SY) was 0.16, 0.30, 0.30 and 0.45 mg/kg DM, respectively. Blood and milk samples were taken at 28 day intervals and at each time point there were positive linear effects of SY on Se concentration in blood and milk. At day 112 blood and milk Se values for T1-T4 were 177, 208, 248, 279 ± 6.6 and 24, 38, 57, 72 ± 3.7 ng/g fresh material, respectively and indicate improved uptake and incorporation of Se from SY. While selenocysteine (SeCys) was the main selenised amino acid in blood its concentration was not markedly affected by treatment, but the proportion of total Se as selenomethionine (SeMet) increased with increasing inclusion rate of SY. In milk, there were no marked treatment effects on SeCys content, but Se source had a marked effect on the proportion of total Se as SeMet. At day 112 replacing SS (T2) with SY (T3) increased the SeMet concentration of milk from 36 to 111 ng Se/g and its concentration increased further to 157 ng Se/g as the inclusion rate of SY increased further (T4) to provide 0.45 mg Se/kg TMR. Neither Se source nor inclusion rate effected the keeping quality of milk. At day 112, milk from T1, T2, and T3 was made into a hard cheese and Se source had a marked effect on total Se and the proportion of total Se comprised as either SeMet or SeCys. Replacing SS (T2) with SY (T3) increased total Se, SeMet and SeCys content from 180 to 340 ng Se/g, 57 to 153 ng Se/g and 52 to 92 ng Se/g, respectively. Key words: dairy cow, milk and cheese, selenomethionine, selenocysteine, milk keeping quality

The effect of soil phosphorus on particulate phosphorus in land runoff

Accumulation of surplus phosphorus (P) in the soil and the resulting increased transport of P in land runoff contribute to freshwater eutrophication. The effects of increasing soil P (19–194 mg Olsen-P (OP) kg−1) on the concentrations of particulate P (PP), and sorption properties (Qmax, k and EPCo) of suspended solids (SS) in overland flow from 15 unreplicated field plots established on a dispersive arable soil were measured over three monitoring periods under natural rainfall. Concentrations of PP in plot runoff increased linearly at a rate of 2.6 μg litre−1 per mg OP kg−1 of soil, but this rate was approximately 50% of the rate of increase in dissolved P (< 0.45 μm). Concentrations of SS in runoff were similar across all plots and contained a greater P sorption capacity (mean + 57%) than the soil because of enrichment with fine silt and clay (0.45–20 μm). As soil P increased, the P enrichment ratio of the SS declined exponentially, and the values of P saturation (Psat; 15–42%) and equilibrium P concentration (EPCo; 0.7–5.5 mg litre−1) in the SS fell within narrower ranges compared with the soils (6–74% and 0.1–10 mg litre−1, respectively). When OP was < 100 mg kg−1, Psat and EPCo values in the SS were smaller than those in the soil and vice-versa, suggesting that eroding particles from soils with both average and high P fertility would release P on entering the local (Rosemaund) stream. Increasing soil OP from average to high P fertility increased the P content of the SS by approximately 10%, but had no significant (P > 0.05) effect on the Psat, or EPCo, of the SS. Management options to reduce soil P status as a means of reducing P losses in land runoff and minimizing eutrophication risk may therefore have more limited effect than is currently assumed in catchment management.

Selenium supplementation of lactating dairy cows: effects on milk production and total selenium content and speciation in blood, milk and cheese

Forty multiparous Holstein cows were used in a 16-week continuous design study to determine the effects of either selenium (Se) source, selenised yeast (SY) (derived from a specific strain of Saccharomyces cerevisiae CNCM 1-3060) or sodium selenite (SS), or Se inclusion rate in the form of SY in the diets of lactating dairy cows on the Se concentration and speciation in blood, milk and cheese. Cows received ad libitum a total mixed ration (TMR) with a 1 : 1 forage: concentrate ratio on a dry matter (DM) basis. There were four diets (T-1 to T-4), which differed only in either source or dose of Se additive. Estimated total dietary Se for T, (no supplement), T-2 (SS), T-3 (SY) and T-4 (SY) was 0.16, 0.30, 0.30 and 0.45 mg/kg DM, respectively. Blood and milk samples were taken at 28-day intervals and at each time point there were positive linear effects of Se in the form of SY on the Se concentration in blood and milk. At day 112 blood and milk Se values for T-1 to T-4 were 177, 208, 248 and 279 +/- 6.6 and 24, 38, 57 and 72 +/- 3.7 ng/g fresh material, respectively, and indicate improved uptake and incorporation of Se from SY. In whole blood, selenocysteine (SeCys) was the main selenised amino acid and the concentration of selenomethionine (SeMet) increased with the increasing inclusion rate of SY In milk, there were no marked treatment effects on the SeCys content, but Se source had a marked effect on the concentration of SeMet. At day 112 replacing SS (T-2) with SY (T-3) increased the SeMet concentration of milk from 36 to 111 ng Se/g and its concentration increased further to 157ng Se/g dried sample as the inclusion rate of SY increased further (T-4) to provide 0.45 mg Se/kg TMR. Neither Se source nor inclusion rate affected the keeping quality of milk. At day 112 milk from T-1, T-2 and T-3 was made into a hard cheese and Se source had a marked effect on total Se and the concentration of total Se comprised as either SeMet or SeCys. Replacing SS (T-2) with SY (T-3) increased total Se, SeMet and SeCys content in cheese from 180 to 340 ng Se/g, 57 to 153 ng Se/g and 52 to 92 ng Se/g dried sample, respectively. The use of SY to produce food products with enhanced Se content as a means of meeting the Se requirements is discussed