Nutrient Retention Efficiency Research Articles

The optimal feeding regime for large yellow croaker Larimichthys crocea, with an emphasis on obviating raw fish diet in commercial farming

Commercial farming of large yellow croaker Larimichthys crocea still relies on raw fish diet. The present study assessed the possibility to replace raw fish diet with a formulated diet containing 490 g/kg crude protein by optimizing feed and feeding management. In experiment I, fish weighing 10.8 g were fed with the formulated diet at either five frequencies (FF13, 1/3 meal/d; FF12, 1/2 meal/d; FF11, 1 meal/d; FF21, 2 meal/d; FF31, 3 meal/d) or at 1 meal/d but different times (FF11, at 6:00; FF11A, at 18:00), respectively. In experiment II, fish were fed at 2 meal/d with the formulated diet (FF21) or a quality raw fish diet (RF21). The final body weight (FBW), weight gain, feed intake and body lipid content, fish in/out ratio (FIFO) and waste outputs (nitrogen, phosphorus and carbon) were higher, whereas the nutrient and energy retention efficiencies (NRE, nitrogen; PRE, phosphorus; CRE, carbon; ERE, energy) were lower, in FF21 and FF31 than in FF13, FF12 and FF11. No significant differences were detected in FBW and weight gain either between FF21 and FF31 or between FF13, FF12 and FF11. The feed conversion ratio (FCR) and feed cost were higher in FF31 than in FF13, FF12 and FF11. The activities of superoxide dismutase (SOD) and catalase (CAT) in plasm, activities of glutathione peroxidase (GSH-PX) and CAT in liver, and malondialdehyde (MDA) content in plasm and liver were higher in FF31 than in FF11. No significant differences were detected in FBW, weight gain, NRE, PRE, CRE, ERE, body composition, feed cost, FIFO-, waste outputs, activities of antioxidant enzymes and MDA content in plasm and liver between FF11 and FF11A despite FF11A had higher feed intake and FCR compared with FF11. The FBW, weight gain, feed intake, FCR, body lipid content, feed cost, FIFO, waste outputs, activities of SOD and GSH-PX in liver, plasm CAT activity, and MDA content in plasm and liver were higher, whereas the survival, NRE, PRE and ERE were lower, in RF21 than in FF21. Our study indicates that 2 meal/d is the optimal feeding frequency for large yellow croaker, and completely replacing raw fish diet with the formulated diet in commercial farming benefits to increase fish survival and yield and to reduce feed cost, FIFO, waste outputs and body lipid deposition.

Feeding and growth stimulation of Penaeus vannamei juveniles: Dose-response to the microbial biomass NovaqPro™ in practical diets

Microbial-based ingredients are gaining in popularity due to their nutritional value and functional properties. The microbial biomass Novacq™ (CA) and commercially produced NovaqPro™ produced in Australia (RA) and Thailand (RT) were assessed at various inclusion rates (2.5–15%) in a basal practical formulation as part of a dose-response study in P. vannamei. The aims were to understand their effect on feed intake and growth performance, their contribution to dietary minerals, their capacity to improve macronutrient retention efficiency, their possible impact on body composition, and ultimately their optimum inclusion rates. Nineteen iso‑nitrogenous and isocalorific diets were fed over 42 days to apparent satiation to 78 tanks each containing 15 juvenile P. vannamei (0.69 g). Shrimp performed well with high survival >91% and weight gain achieved on the basal diet (0.21 g d−1) improved on all treatments (except 2.5% CA) up to 30% higher for CA and 60% higher for RA and RT. The growth responses were curvilinear and a plateau in growth performance was determined at 8.9 ± 0.6% and 12.8 ± 1.2% NovaqPro™ inclusion rates for broken-line and quadratic models, respectively. The response plateaued earlier at circa 7.5% inclusion for the original Novacq™. FCR (1.33 average) and nutrient retention efficiency (RE average of 33%, 21% and 23% for crude protein, total lipid and gross energy respectively), were largely unaffected by inclusion rates up to 10%. The highest energy retention efficiency was achieved in feeds containing 7% NovaqPro™. Feed intake stimulation was the major mode of action of the microbial biomass in this study, with feed intake, from as early as day 5, mirroring the growth trends. The graded inclusions of NovaqPro™ in diets also resulted in increases in dietary mineral composition which correlated to culture performance. However, further comparative analyses between the response against CA and RA/RT demonstrated that the supply of biologically relevant macro and micro minerals from the microbial biomass was unlikely on its own to be the primary driver of the dose-response observed. Inclusions between 7% and 9% of NovaqPro™ in practical diets to achieve the highest performance and nutritional benefits are recommended.

Stoichiometry on the edge—humans induce strong imbalances of reactive C:N:P ratios in streams

Anthropogenic nutrient inputs led to severe degradation of surface water resources, affecting aquatic ecosystem health and functioning. Ecosystem functions such as nutrient cycling and ecosystem metabolism are not only affected by the over-abundance of a single macronutrient but also by the stoichiometry of the reactive molecular forms of dissolved organic carbon (rOC), nitrogen (rN), and phosphorus (rP). So far, studies mainly considered only single macronutrients or used stoichiometric ratios such as N:P or C:N independent from each other. We argue that a mutual assessment of reactive nutrient ratios rOC:rN:rP relative to organismic demands enables us to refine the definition of nutrient depletion versus excess and to understand their linkages to catchment-internal biogeochemical and hydrological processes. Here we show that the majority (94%) of the studied 574 German catchments show a depletion or co-depletion in rOC and rP, illustrating the ubiquity of excess N in anthropogenically influenced landscapes. We found an emerging spatial pattern of depletion classes linked to the interplay of agricultural sources and subsurface denitrification for rN and topographic controls of rOC. We classified catchments into stoichio-static and stochio-dynamic catchments based on their degree of intra-annual variability of rOC:rN:rP ratios. Stoichio-static catchments (36% of all catchments) tend to have higher rN median concentrations, lower temporal rN variability and generally low rOC medians. Our results demonstrate the severe extent of imbalances in rOC:rN:rP ratios in German rivers due to human activities. This likely affects the inland-water nutrient retention efficiency, their level of eutrophication, and their role in the global carbon cycle. Thus, it calls for a more holistic catchment and aquatic ecosystem management integrating rOC:rN:rP stoichiometry as a fundamental principle.

Vegetated urban streams have sufficient purification ability but high internal nutrient loadings: Microbial communities and nutrient release dynamics

The release of nutrients back into the water column due to macrophyte litter decay could offset the benefits of nutrient removal by hydrophytes within urban streams. However, the influence of this internal nutrient cycling on the overlying water quality and bacterial community structure is still an open question. Hence, litter decomposition trials using six hydrophytes, Typha latifolia (TL), Phragmites australis (PAU), Hydrilla verticillata (HV), Oenanthe javanica (OJ), Myriophyllum aquaticum (MA), and Potamogeton crispus (PC), were performed using the litterbag approach to mimic a 150-day plant litter decay in sediment-water systems. Field assessment using simple in/out mass balances and uptake by plant species was carried out to show the potential for phytoremediation and its mechanisms. Results from two years of monitoring (2020–2021) indicated mean total nitrogen (TN) retention efficiencies of 7.2–60.14 % and 9.5–55.6 % for total phosphorus (TP) in the studied vegetated urban streams. Nutrient retention efficiencies showed temporal variations, which depended on seasonal temperature. Mass balance analysis indicated that macrophyte assimilation, sediment adsorption, and microbial transformation accounted for 10.31–41.74 %, 0.84–3.00 %, and 6.92–48.24 % removal of the inlet TN loading, respectively. Hydrophyte detritus decay induced alterations in physicochemical parameters while significantly increasing the N and P levels in the overlying water and sediment. Decay rates varied among macrophytes in the order of HV (0.00436 g day−1) > MA (0.00284 g day−1) > PC (0.00251 g day−1) > OJ (0.00135 g day−1) > TL (0.00095 g day−1) > PAU (0.00057 g day−1). 16S rRNA gene sequencing analysis showed an increase in microbial species richness and diversity in the early phase of litter decay. The abundances of denitrification (nirS and nirK) and nitrification (AOA and AOB) genes also increased in the early stage and then decreased during the decay process. Results of this study conducted in seven urban streams in northern China demonstrate the direct effects of hydrophytes in encouraging nutrient transformation and stream self-purification. Results also demonstrate that macrophyte detritus decay could drive not only the nutrient conversions but also the microbial community structure and activities in sediment-water systems. Consequently, to manage internal sources and conversions of nutrients, hydrophytic detritus (e.g., floating/submerged macrophytes) must be suppressed and harvested.

Total Replacement of Fish Meal by the Combination of Fish Residue Meal and Soy Protein from Soymilk in the Diet of Red Sea Bream (Pagrus major).

Three experiments were performed to explore (i) the complete replacement of fish meal (FM) with a combination of fish residue meal (FRM, 65% round discarded fish + 35% byproduct), soy protein concentrate (SPC) from soymilk and corn gluten meal (CGM) in Trial 1 and (ii) the utilization of diets composed of increasing byproducts in FRM in the summer (Trial 2) and winter (Trial 3) seasons. In Trial 1, the ratio of (SPC + CGM):FM in the control diet (C) was 8:2. The FM component from diet C was replaced with FRM (diet, RM20), where the ratio of (SPC + CGM):FRM became 8:2, and this ratio was changed to 6:4, 4:6 and 2:8, and referred to as RM40, RM60 and RM80, respectively. In Trials 2 and 3, the ratios of round discarded fish and byproducts in FRM were adjusted to 65:35 (FRM1), 30:70 (FRM2) and 0:100 (FRM3), and the FRM component from diet RM40 in Trial 1 was replaced with FRM1, FRM2 and FRM3 to formulate diets RM1, RM2 and RM3, respectively. In Trials 1, 2 and 3, rearing periods were 10, 8 and 12 weeks, respectively. In Trials 1 and 3, there were no significant differences in growth parameters, nutrient retention efficiency or plasma constituents among the treatments, irrespective of the inclusion levels of FRM in the diets (p > 0.05). Although there were no significant differences in final mean weight (p > 0.05), daily feeding rate and feed conversion ratio in diet RM3 were significantly higher and lower, respectively, compared to the control group in Trial 2 (p < 0.05). These results suggest that FM can be entirely replaced with FRM, and that the total elimination of round discarded fish from FRM does not affect growth or health status in red sea bream either in summer or winter seasons.

Potential for high contribution of urban gardens to nutrient export in urban watersheds

Urban gardens and farms typically use compost as a source of nutrients, often at levels that exceed crop nutrient demands. Although land dedicated to agriculture is a small fraction of urban land use, high input rates coupled with low nutrient use efficiencies suggest that export of nitrogen (N) and phosphorus (P) from this land could be potentially important contributors to urban nutrient budgets. We used the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) Nutrient Delivery Ratio model to examine the potential impact of garden density, compost input rates, and nutrient retention efficiency on N and P export from stormwater runoff for a 737-ha urban residential area in Saint Paul, Minnesota. Although gardens and farms accounted for 0.1-0.5% of land area in our scenarios, compost inputs accounted for as much as 33% of N inputs and 85% of P inputs to the urban landscape. The contribution of gardens to urban nutrient export through stormwater runoff is highly dependent on modeled maximum retention efficiency values. If retention efficiency is high, gardens with low compost inputs are similar to other vegetated land uses in contributions to nutrient export, but gardens become significant contributors to watershed P export if compost inputs are high, or if retention efficiency drops to 75% or lower. These results underscore mass-balance constraints inherent in urban nutrient recycling and highlight the importance of understanding the long-term fate of excess nutrients applied to urban landscapes.

Influence of Biochar Application on Soil Nitrate Leaching and Phosphate Retention: A Synthetic Meta-analysis

How to control non-point source pollution caused by leaching of soil nitrate and phosphate from agricultural land is currently an extremely important global environmental problem facing human society. Biochar, a carbon-rich material produced from various organic feedstocks using thermochemical technologies, has attracted much attention because of its great potential in soil improvement. Many studies have been carried out to investigate the effects of biochar application on the retention, utilization, and use efficiency of soil nutrients. Unfortunately, the results from individual experimental studies regarding the effects of biochar on soil nitrate leaching and phosphate retention differed greatly. Consequently, the underlying mechanisms related to reduction in nitrate and phosphate leaching/retention by biochar application, as well as the appropriate preparation conditions (or biochar type), remain unclear. In this study, the effects of biochar application on soil nitrate leaching and phosphate retention were systematically examined using the method of Meta-analysis (MA); based on these results, the inhibition mechanisms for nitrate leaching and enhancement mechanisms for phosphate retention were also explored. In total, 149 paired datasets from 41 articles and 180 paired datasets from 36 articles were collected for nitrate and phosphate, respectively. The MA results demonstrated that, regardless biochar and soil properties, biochar application could significantly reduce soil nitrate leaching by 37.1% and increase soil phosphate retention by 20.8%. Furthermore, the C/N ratio of biochar, heating treatment temperature, and biochar application amount indicated a significant effect on the response of soil nitrate leaching to biochar application. The specific surface area of biochar, heating treatment temperature, and soil organic carbon content had a significant effect on the response of soil phosphate retention to biochar application. Based on the results from MA, the potential mechanisms of soil nitrite leaching reduction and phosphate retention enhancement were further explored from different perspectives. Lastly, the biochars prepared from straw or wood materials and pyrolyzed at a medium temperature (400-600℃) or high temperature (>600℃) were recommended for reducing soil nitrate leaching and improving soil phosphate retention, respectively. In sum, the results presented in this study can provide a scientifically theoretical basis for the practical application of biochar in the control of soil non-point source pollution of nitrate and phosphate.

Different dietary ratios of arginine, methionine and lysine for turkeys: effects on whole-body composition and nutrient utilization efficiency in the early growth stage

Abstract The growth rate, tissue development and health status of turkeys are affected by the dietary supply of essential amino acids (AAs) such as lysine (Lys), methionine (Met) and arginine (Arg). According to various guidelines, the diets fed to turkeys in the first 4 weeks of the rearing period should contain 1.60–1.76% Lys, 1.60–1.80% Arg and 0.55–0.70% Met. This study investigated the effects of different ratios of Arg and Met in starter diets with 1.60% of Lys content, i.e. a low level, on the whole-body composition of turkeys and nutrient retention efficiency. The experiment lasted for 28 days and it had a two-factorial randomized design with three levels of Arg (90%, 100% and 110%) and two levels of Met (30% or 45%), relative to the content of dietary Lys, with six groups of eight replicates per group and 18 turkeys per replicate. Different dietary Arg and Met levels, relative to Lys, did not affect AA concentrations in the body protein or the proximate whole-body composition (crude protein, crude fat, gross energy and ash) of turkeys. The higher Met level positively influenced energy, protein and Arg utilization and their retention efficiency as well as the growth performance of turkeys. An increase in the dietary level of Arg to 100% and 110% of Lys content had no influence on the growth performance of turkeys and it reduced the retention efficiency of Arg. Differences in the body weight gain, feed intake and Lys utilization of turkeys fed diets with different Arg levels resulted also from the strong interaction between Met and Arg levels. At the lower level of Met in the diet, a decrease in Arg relative to Lys from 100% to 90% resulted in decreased (P = 0.003) feed intake (from 50.34 g to 46.72 g) and growth rate (from 31.84 g to 29.79 g), which was not noted for the higher Met content (45% relative to Lys). At the lowest level of Arg in the diet (90% of Lys content), a decrease in Met relative to Lys from 45% to 30% caused a decrease in Lys retention efficiency (from 61.51% to 56.29%). The results of this study suggest that the higher content of Met in the diet (45% to Lys) and the Arg level corresponding to 90% of Lys content contribute to optimizing nutrient retention efficiency in turkeys during the first 28 days of their life.

Anthropogenic regulation governs nutrient cycling and biological succession in hydropower reservoirs

Hydropower plays an important role in the supply of renewable energy, but it also exerts a great influence on the river continuum. Understanding nutrient cycling and microbial community succession in hydropower reservoirs is key to weighing hydroelectric pros and cons. However, the underlying control mechanisms are still not well known, especially with respect to the impacts of hydrological conditions. Based on a comprehensive survey of hydropower reservoirs along the Wujiang River in SW China and an integration of published data, we found that reservoir physicochemical and biological stratifications and planktonic microbial community assembly were synergistically evolving, and reservoir hydraulic load (i.e., mean water depth per unit retention time) was a key factor controlling the strength of stratifications, CO2 and N2O fluxes, nutrient retention efficiency, and bacterioplankton diversity. Hydraulic loads are artificially designed for hydropower reservoirs, and nutrient cycling and biological succession in reservoirs are thus governed by anthropogenic regulation. This study provides a theoretical basis to mitigate the environmental impacts of hydropower dams by regulating reservoir hydraulic load.

Nutrient retention efficiencies in integrated multi‐trophic aquaculture

AbstractOne of the bottlenecks for commercial implementation of integrated multi‐trophic aquaculture (IMTA) is the difficulty in quantifying its environmental performance. We reviewed a large body of literature to determine the variability in nutrient dynamics within different IMTA systems (open sea‐cages, land‐based flow‐through and recirculating aquaculture systems), with the aim to provide a generic framework to quantify nutrient retention efficiencies in integrated aquaculture systems. Based on the eco‐physiological requirements of the cultured species, as well as the response of “extractive” species to waste from “fed” species, the maximum retention efficiency was defined for a conceptual four‐species marine IMTA system (fish–seaweed–bivalve–deposit feeder). This demonstrated that 79%–94% of nitrogen, phosphorus and carbon supplied with fish feed could theoretically be retained. In practice, however, various biological and environmental factors may limit retention efficiencies and thereby influence the bioremediation of IMTA systems. These biological (waste production, stoichiometry in nutrient requirements) and environmental (temporal and spatial connectivity) factors were therefore evaluated against the theoretical reference frame and showed that efficiencies of 45%–75% for closed systems and 40%–50% for open systems are more realistic. This study is thereby the first to provide quantitative estimates for nutrient retention across IMTA systems, demonstrating that a substantial fraction of nutrients released from fish culture units can be retained by extractive species and subsequently harvested. Furthermore, by adapting this framework to the design and the condition prevailing for a specific IMTA system, it becomes a generic tool to analyse the system's bioremediation potential and explore options for further improvement.

Dietary replacement of fishmeal with commercial protein blends designed for aquafeeds in hybrid striped bass (Morone chrysops ♂× Morone saxatilis ♀): Digestibility, growth, body composition, and nutrient retention

Four commercial protein blends—Elite 60™, Elite 65™, Elite 70™, and Pro-Cision™ (HJ Baker & Bros., Inc., Tuscola, Texas, USA)—were evaluated in hybrid striped bass (HSB) for nutrient digestibility and fishmeal (FM) replacement value. A control diet was formulated like a commercial HSB feed containing 17% FM that met or exceeded the nutritional requirements of HSB. Commercial blends replaced FM in the control diets on an ideal protein basis by supplementing the first-three limiting amino acids (methionine, lysine, threonine). Diets were formulated on a digestible protein basis (38% digestible protein), isolipidic (16%), and contained 10% lipid from marine fish sources. Fish fed the control diet generally exhibited better growth and nutrient utilization responses than the other diets. Responses to the Elite™ products were intermediate, while Pro-Cision™ lagged in both digestibility and growth responses. Digestibility of gross nutrients in each of the test products did not differ significantly from those of FM, but protein was significantly more digestible in Elite 70™ compared to that of FM and Pro-Cision™. Availabilities of leucine, phenylalanine, tyrosine, and valine in Pro-Cision™ were significantly less (92.2%, 91.3%, 91.0%, and 91.5%, respectively) than those in FM (96.1%, 96.8%, 94.6%, and 94.5%, respectively). Fish fed the Pro-Cision™ diet exhibited significantly lower cumulative feed intake, average weight, and muscle ratio compared to fish fed all other diets. Elite 60™, Elite 65™, and Elite 70™ fish did not differ in intraperitoneal fat or muscle ratio compared to fish fed the control diet. Fish fed all three Elite™ diets had significantly lower average weight (52.5–57.9 g) compared to fish fed the control diet (73.2 g). There were no differences in arginine and histidine whole-body nutrient retention among dietary treatments, while other nutrient retention efficiencies did differ across treatments. Nutrient retention of the averaged essential amino acids was not significantly different in fish fed Elite 70™ compared to fish fed the control diet. There were no significant differences in lysozyme activity and mean corpuscular hemoglobin concentration among treatments. It appears that Pro-Cision™ is not an attractive alternative to FM in HSB diets considering total feed intake, growth, and nutrient and energy retentions. However, Elite 65™ and Elite 70™ may be potential FM alternatives in HSB diets despite differences in growth performance after 13-weeks.

Macro- and Micronutrient Cycling and Crucial Linkages to Geochemical Processes in Mangrove Ecosystems

High mangrove productivity is sustained by rapid utilization, high retention efficiency and maximum storage of nutrients in leaves, roots, and soils. Rapid microbial transformations and high mineralization efficiencies in tandem with physiological mechanisms conserve scarce nutrients. Macronutrient cycling is interlinked with micronutrient cycling; all nutrient cycles are linked closely to geochemical transformation processes. Mangroves can be N-, P-, Fe-, and Cu-limited; additions of Zn and Mo stimulate early growth until levels above pristine porewater concentrations induce toxicity. Limited nutrient availability is caused by sorption and retention onto iron oxides, clays, and sulfide minerals. Little N is exported as immobilization is the largest transformation process. Mn and S affect N metabolism and photosynthesis via early diagenesis and P availability is coupled to Fe-S redox oscillations. Fe is involved in nitrification, denitrification and anammox, and Mo is involved in NO3− reduction and N2-fixation. Soil Mg, K, Mn, Zn and Ni pool sizes decrease as mangrove primary productivity increases, suggesting increasing uptake and more rapid turnover than in less productive forests. Mangroves may be major contributors to oceanic Mn and Mo cycles, delivering 7.4–12.1 Gmol Mn a−1 to the ocean, which is greater than global riverine input. The global Mo import rate by mangroves corresponds to 15–120% of Mo supply to the oceanic Mo budget.

Nutrient mass balance of a large riverine reservoir in the context of water residence time variability.

The excessive input of nitrogen (N) and phosphorus (P) from anthropogenic activities is the main reason behind the cultural eutrophication and algal blooms in freshwater ecosystems. Here, I present a comprehensive budget of N, P for a large reservoir (Lake Diefenbaker) within a highly cultivated watershed. I constructed a 4-year nutrient budget from 2011 to 2014, using grab samples and daily flow data, and a multi-decadal (1978 through 2014) budgeting to examine the effect of inter-annual variability of water residence time on retention of N and P, and if retention of N and P is affected differently. The 4-year budget showed that the reservoir was a net source of total nitrogen (TN) during 2011 and 2014, but a net sink during 2012 and 2013. This resulted in retention coefficients of - 35% and - 4% in 2011 and 2014, respectively. With respect to the total phosphorus (TP) budget, the reservoir acted as a net sink in all 4 years, with a mean retention coefficient of 87%. Consistent with findings of the 4-year budget, the results of the multi-decadal budgeting showed that the reservoir was a net sink for TP during the period of record with a mean retention of 81% (1583 t/year). Regarding TN, the mean retention was lower (49%, 4836 t/year) and more variable relative to TP over the long term. Unlike TP, the results showed that the retention of TN has been decreasing noticeably since 1978. Overall, the retention of TP in this lake is primarily controlled by in-lake sedimentation and most likely does not change substantially in response to inter-annual variation of hydraulic variables such as water residence time. For TN, the role of sedimentation could be minor in retention process in this reservoir (or similar reservoirs elsewhere), but in-lake biological processes could play a more important role. These findings are useful for understanding the role of larger reservoirs with water residence time of 1-3 years in nutrient retention and how changes in flow and water residence time due to climate variability and water management can influence the nutrient retention efficiency.

Biomass harvesting leads to soil acidification: a study of mixed crop–livestock farming systems in Madagascar

Soil acidification and declining fertility are widespread in sub‐Saharan Africa. Nutrient depletion is mainly related to nutrient mining driven by biomass removal without replenishment of nutrients through use of fertilisers. Concomitant acidification is due to the high ash alkalinity of harvested biomass. We determined the nutrient content and ash alkalinity of biomass of the main crops produced in smallholder mixed crop–livestock farming systems in the Malagasy Highlands of Madagascar and calculated the soil acidification/alkalinisation occurring through biomass transfer. Samples of rice and forage were collected from 70 rice plots and 91 cultivated forage plots, and 70 manure samples were collected from farms. Nutrient exports induced by crop harvesting resulted in annual losses of 57 kg nitrogen (N), 6 kg (phosphorus) P and 33 kg potassium (K) ha–1 for rice (grain + straw), and 31–51 kg N, 8–9 kg P and 29–57 kg K ha–1 for each forage cut (with three cuts per year on average). The ash alkalinity of samples, calculated as the difference between cation and anion contents, was 49–100 cmolc kg–1 for forage crops, 31 cmolc kg–1 for rice straw, and only 4 cmolc kg–1 for rice grains. Biomass removal caused a loss of nutrients and an increase in soil acidity. Owing to low nutrient retention efficiency during the handling and storage of manure, the traditional input of manure at 5 t fresh matter ha–1 is insufficient to balance nutrient and alkalinity losses in Malagasy mixed crop–livestock farming systems. Maintaining productive and sustainable mixed crop–livestock farming systems requires greater attention to ensuring a nutrient balance at both plot and farm levels.

Retention of nitrogen and phosphorus in Lake Chaohu, China: implications for eutrophication management.

Nutrient retention is an important process in lake nutrient cycling of lakes and can mitigate lake eutrophication. However, little is known about temporal lake nutrient retention efficiency and it varies due to changes in hydrological, ecological, and nutrient inputs to lake waters. Quantitative information about seasonal lake N and P retention is critical for developing strategies to reduce eutrophication in lake systems. This study investigated TN and TP retention efficiencies and retention masses using water and mass balance calculations, and statistically analyzed the seasonal variability of nutrient retention in Lake Chaohu, China, from 2014 to 2018. Lake Chaohu experienced large amounts of external loads inputs (23.2gNm-2year-1 and 1.3g P m-2year-1), and approximately 58% TN and 48% TP were retained annually. The lake acted more as a sink for N than for P. The mean annual TP retention efficiency decreased (P < 0.05) over the study period, indicating that TP retention capacity was gradually exceeded. Seasonal variability of TN and TP retention efficiency was high and ranged from - 18.7 to 144.1% and from - 58.8 to 170.7%, respectively, over the five study years. The internal P loads over the study period were equivalent to roughly 9% of the total external loads. The annual nutrient retention efficiency of TN and TP increased with hydraulic residence time, while water temperature was an essential factor for the contrasting seasonal variation patterns of TN and TP retention efficiencies.

Dietary butyrate alone or in combination with succinate and fumarate improved survival, feed intake, growth and nutrient retention efficiency of juvenile Penaeus monodon

Organic acids and their salts have been used in commercial aquafeeds as an alternative to antibiotics, growth promoters and their effect on performance and survival continue to be investigated in aquatic organisms including shrimp with a few reports on Penaeus monodon. We assessed production performance and nutrient retention efficiency of juvenile black tiger shrimp fed diets supplemented without (control – CON) or with organic acids (butyrate - BUT, succinate – SUC, and fumarate - FUM) individually (10 g kg−1) or in combination (ALL; 30 g kg−1). After 42 days, survival was significantly higher in the BUT and ALL treatments compared to the CON (98% and 90% vs. 70%; P < .01). Addition of BUT, SUC, and ALL reduced feed conversion ratio compared to the CON group (1.3–1.7 vs. 2.4; P < .01). Biomass gain in BUT and ALL feeds was statistically higher than the rest of the dietary treatments (28.3 g vs. 11.2–19.1 g; P < .01). Non-linear and linear regressions displayed a strong relationship between biomass gain and total feed intake across dietary treatments with R2 varying from 0.71 to 0.99. The supplementation of SUC, BUT, and ALL increased the overall nutrient retention efficiency (RE) in comparison to the CON, with BUT and ALL displaying the highest RE for all tested macronutrients (e.g., crude protein = 26.7% and 24.6% vs. 15.3%, total lipid = 19.2% and 17.7% vs. 10.6%, ash = 25.1% and 23.1% vs. 12.1%, and gross energy = 17.7% and 16.3% vs. 10.2%). In summary, supplementation of ALL organic acids (fumarate, butyrate, and succinate) improved survival, feed intake, growth, and nutrient retention efficiency of juvenile P. monodon. Individually, BUT appears to be the most potent organic acid followed by SUC, whereas the use FUM isn't justified in P. monodon diets.

Effect of ultrasound‐ethanol pretreatment on drying kinetics, quality parameters, functional group, and amino acid profile of apple slices using pulsed vacuum drying

AbstractThe influence of ultrasound‐ethanol (US‐E) pretreatment durations (10, 20, and 30 min) on apple slices dried with varied temperatures (60, 70, and 80°C) using pulsed vacuum dryer was investigated. The results showed that untreated sample (control) took 375, 325, and 225 min to achieve a constant weight of drying whereas drying time for 30 US‐E samples were 275, 225, and 175 min, indicating that 30 US‐E reduced the total drying time by 26.66, 30.77, and 22.22% at 60, 70, and 80°C, respectively. Moisture effective diffusivity and activation energy were in the range of 1.98–4.08 × 10−8 m2/s and 12.58–23.43 kJ/mol, respectively. Color (L*, a*, b*) and texture were affected significantly (p &lt; .05) at high temperature and longer US‐E. Shorter US‐E duration and lower temperature could preserve most functional groups. Also, total free amino acid values were significantly higher at lower temperature and longer US‐E pretreatment.Practical applicationsDrying time, nutrient retention, and energy efficiency are at the heart of the food industry. The remarkable reduction obtained in the drying time as well as retaining of some functional groups (nutrients composition) with the use of ultrasound‐ethanol as a pretreatment for pulsed vacuum dryer indicates that this technique will serve a great purpose in food processing industries. This in effect will reduce production cost thereby making the business operations of food processors competitive as it provides value proposition to their customers.

An advanced Escherichia coli phytase improves performance and retention of phosphorus and nitrogen in rainbow trout (Oncorhynchus mykiss) fed low phosphorus plant-based diets, at 11 °C and 15 °C

Two studies were conducted to evaluate the effect of phytase supplementation on the overall performance and nutrient retention efficiency of rainbow trout (Oncorhynchus mykiss) fed low-phosphorus (P) plant-based diets at water temperatures of 11 °C and 15 °C. In the first experiment at 11 °C, trout (average weight 56 g) were allocated to one of 4 dietary treatments, with 3 replicate 200L tanks per diet and 35 fish per tank. In the second experiment (15 °C), trout (average weight 42 g) were allocated to one of 3 dietary treatments, with 3 replicate 200L tanks per diet and 34 fish per tank. Diets were fed to satiation over a 75 or 83 day period for experiment 1 and 2, respectively. Treatments included a low-P diet (NC), with no added monocalcium phosphate (MCP), supplemented with 0, 500 or 2500 FTU/kg phytase (Quantum Blue). Experiment 1 also included a diet adequate in P (PC) with 1.8% MCP inclusion. In both experiments, feeding phytase linearly increased (P < 0.01) weight gain of fish fed NC diets. Feeding phytase at 2500 FTU/kg improved weight gain of fish exposed to water temperatures of 11 °C and 15 °C by 36% and 45%, respectively, compared to the respective NC. Feed conversion ratio (FCR) was also improved (linear, P < 0.001) by 14% with phytase supplementation at 15 °C. At water temperatures of 11 °C, supplementing phytase to the NC diet improved N retention (P < 0.05) beyond that of the non-supplemented NC and PC diets. Furthermore, 2500 FTU/kg phytase increased P digestibility by 56 and 27 percentage points, and P retention by around 29 and 17 percentage points, compared to the NC and PC, respectively. Consequently, supplementing 2500 FTU/kg phytase reduced (linear, P ≤ 0.001) N and P excretion by 13% and 55%, respectively, compared to the PC. At 15 °C, addition of phytase to the low-P diet increased (quadratic, P < 0.017) N and P retention in trout by approximately 4 and 24 percentage points, respectively. Supplementing phytase to the low-P diet reduced N (linear, P ≤ 0.001) and P (Quadratic, P < 0.01) excretion in trout, with addition of 2500 FTU/kg lowering excretion of these nutrients by 19% and 42%, respectively. These findings demonstrate the efficacy of an enhanced Escherichia coli phytase, even at low water temperatures, to support performance of trout fed low-P diets, while enhancing P and protein utilization and lessening environmental pollution.

Protein, amino acid and energy utilisation of juvenile Yellowtail Kingfish (Seriola lalandi): Quantifying abiotic influences

Two experiments were conducted to evaluate the effect of abiotic factors on the digestible nutrient and energy utilisation of juvenile Yellowtail Kingfish (YTK). Experiment 1 considered the effect of temperature at 15 °C or 24 °C. Experiment 2 considered the effect of dissolved oxygen (DO) at 60% or 100% saturation at 20 °C. Duplicate groups of YTK per feed treatment (initial body weight Experiment 1 = 187.2 ± 0.4 g fish−1; Experiment 2 = 220.9 ± 2.35 g fish−1) were fed a commercial diet at one of five ration levels. Feeding levels ranged from a restricted ration, equivalent to approximately 10% of satiation feeding, through to maximal satiation feeding. Feed trials were run over 35–38 days. Growth and nutrient deposition, feed intake and diet digestibility were assessed to establish nutrient retention efficiencies and maintenance requirements. Temperature was shown to have a varying effect on utilisation responses in YTK with the magnitude of the response dependent on the nutrient examined. Maintenance requirements of all nutrients generally increased with increasing temperature. Low DO at 60% saturation negatively affected the nutrient and energy utilisation efficiencies in YTK with this response tending to be more pronounced with increasing nutrient and energy intake. However DO level did not significantly affect feed intake. This study provides insight into the effects of abiotic factors on the nutritional physiology of YTK. Data generated from this study can be used to improve feed models for YTK facilitating better feed management and feed formulation through greater understanding of the influence of abiotic conditions on nutrient demand and utilisation.

Embedded reservoir and constructed wetland for drinking water source protection: Effects on nutrient removal and phytoplankton succession

An embedded reservoir that provides an efficient nutrient removal system protects drinking water. However, embedded reservoirs are rarely used in eutrophic shallow lakes because of their undetermined nutrient retention efficiency and unknown effects by the phytoplankton community. In this study, we aim to investigate the nutrient retention and algae succession in an embedded reservoir and adjacent wetland from April 2017 to September 2018 in the eastern part of Lake Taihu, China. More than 40% of total phosphorus (TP) and 45% of particulate phosphorous entering the reservoir were retained semi-annually, and the highest TP removal efficiency was achieved in the reservoir during autumn with an average value of 53.3% ± 9.9%. The overall nitrogen retention efficiency (21.7% ± 37.8%) was lower than that of TP (41.8% ± 27.8%). Similar trends were obtained in the wetland area. An important pathway for phosphorus removal is through particulate matter retention. Our study revealed that nutrient retention mechanisms in the reservoir were primarily via macrophyte absorption, particulate substance sedimentation, and prolonged water residence time. Consequently, the phytoplankton biomass (Chl-a) in the reservoir decreased (from 48.0 to 25.2 μg/L) and water transparency improved, due to the decreased P level and transformation of the phytoplankton group into simple structures with good ecological status. Therefore, the combination of embedded reservoir and constructed wetland ecosystem can be used successfully to protect surface water. The results will be advantageous to groups seeking to preserve drinking water sources.