Feed comprises the biggest cost in intensive fish farming and the quality of feed is therefore important. A vast body of research has been carried out in order to investigate nutritional quality of alternative ingredients. Effects of ingredients on physical quality are seldom included in these investigations. Physical quality of feed varies with ingredient composition and processing condition and may interfere with feed intake, nutrient digestibility and therefore growth performance of the fish. In this review, physical quality of extruded, high energy feed, and how ingredient composition and processing conditions affect the quality will be addressed. Various pellet properties will be discussed and methods used to evaluate physical quality will be reviewed.

A review of the effects of ingredient composition and processing conditions on the physical qualities of extruded high‐energy fish feed as measured by prevailing methods

Combined effects of dietary phytase and organic acid on growth and phosphorus utilization of juvenile yellow catfish Pelteobagrus fulvidraco

Phytases have been employed in animal feeds for several years, used primarily for reducing the environmental impact and phosphorus loads of farm effluents. Beneficial effect of dietary phytase has been associated with the limited ability of monogastric animals to utilize dietary plant phytates. To date, numerous studies have shown the positive effect of phytase supplementation on the availability of dietary phosphorus and trace minerals within plant-based feeds for monogastric farm animals, including farmed fish and shrimp. Individual feed ingredients may also be improved with phytases as an exogenous treatment, also termed pre-conditioning dephytinization prior to mixing. This review presents data on the potential benefit of phytase application for fish and shrimp species in improving digestibility of phosphorus and other minerals as well as organics nutrient fractions such as protein, amino acids and lipids.

Use of phytases in fish and shrimp feeds: a review

Manganese (Mn) is a biologically important and redox-active metal that may exert a poorly recognized control on carbon (C) cycling in terrestrial ecosystems. Manganese influences ecosystem C dynamics by mediating biochemical pathways that include photosynthesis, serving as a reactive intermediate in the breakdown of organic molecules, and binding and/or oxidizing organic molecules through organo-mineral associations. However, the potential for Mn to influence ecosystem C storage remains unresolved. Although substantial research has demonstrated the ability of Fe- and Al-oxides to stabilize organic matter, there is a scarcity of similar information regarding Mn-oxides. Furthermore, Mn-mediated reactions regulate important litter decomposition pathways, but these processes are poorly constrained across diverse ecosystems. Here, we discuss the ecological roles of Mn in terrestrial environments and synthesize existing knowledge on the multiple pathways by which biogeochemical Mn and C cycling intersect. We demonstrate that Mn has a high potential to degrade organic molecules through abiotic and microbially mediated oxidation and to stabilize organic molecules, at least temporarily, through organo-mineral associations. We outline research priorities needed to advance understanding of Mn-C interactions, highlighting knowledge gaps that may address key uncertainties in soil C predictions.

A Critical Review on the Multiple Roles of Manganese in Stabilizing and Destabilizing Soil Organic Matter

Chemical etching fabrication of uniform mesoporous Bi@Bi2O3 nanospheres with enhanced visible light-induced photocatalytic oxidation performance for NOx

As important components with excellent oxidation and adsorption activity in soils and sediments, manganese oxides affect the transportation and fate of nutrients and pollutants in natural environments. In this work, birnessite was formed by photocatalytic oxidation of Mn2+aq in the presence of nitrate under solar irradiation. The effects of concentrations and species of interlayer cations (Na+, Mg2+, and K+) on birnessite crystal structure and micromorphology were investigated. The roles of adsorbed Mn2+ and pH in the transformation of the photosynthetic birnessite were further studied. The results indicated that Mn2+aq was oxidized to birnessite by superoxide radicals (O2•-) generated from the photolysis of NO3- under UV irradiation. The particle size and thickness of birnessite decreased with increasing cation concentration. The birnessite showed a plate-like morphology in the presence of K+, while exhibited a rumpled sheet-like morphology when Na+ or Mg2+ was used. The different micromorphologies of birnessites could be ascribed to the position of cations in the interlayer. The adsorbed Mn2+ and high pH facilitated the reduction of birnessite to low-valence manganese oxides including hausmannite, feitknechtite, and manganite. This study suggests that interlayer cations and Mn2+ play essential roles in the photochemical formation and transformation of birnessite in aqueous environments.

Photochemical Formation and Transformation of Birnessite: Effects of Cations on Micromorphology and Crystal Structure.

The effects of supplemental graded levels of neutral phytase using pretreatment and spraying methods on the apparent digestibility coefficients (ADCs) of protein, minerals and amino acids were investigated in grass carp (Ctenopharyngodon idellus) (mean weight, 20.92 ± 1.04 g). Seven experimental diets were prepared as: no-phytase supplementation (control), pretreatment with phytase dose of 500 U (PP500), 1000 U (PP1000) and 1500 U (PP1500) per kg diet. With spraying method, the phytase was added to feed at the same three grades, namely 500 U (PS500), 1000 U (PS1000) and 1500 U (PS1500) per kg diet. After an 8-week feeding trial, addition of phytase improved the crude protein, crude lipid, dry matter, ash, phosphorus and calcium digestibilities in comparison with the control, especially in the diets where phytase addition level was above 1000 U kg−1 (P < 0.05). Phytase supplementation, both the pretreatment and spraying, significantly enhanced the ADCs of essential amino acid (EAA) and non-essential amino acid. The ADCs of the nutrients were significantly influenced by phytase supplementation methods, supplementation levels and interaction of methods and levels. Based on the results, supplemental dietary phytase, regardless of application methodology, improved the ADCs of nutrients in grass carp, and the pretreatment mode of phytase application was more effective than spraying at the same phytase level. We suggest that the optimal level of phytase pretreatment is 1000 U kg−1 diet, and the best addition level of phytase spraying is 1500 U kg−1 diet or more phytase is required for spraying.

Apparent digestibility of nutrients in grass carp (Ctenopharyngodon idellus) diet supplemented with graded levels of neutral phytase using pretreatment and spraying methods

During the application of in situ thermal desorption technology (ISTD), heat in some areas often can not be effectively utilized. Nevertheless, the heat in these areas might promote the biodegradation of polycyclic aromatic hydrocarbons (PAHs). However, few studies have concentrated on the effect of temperature on biodegradation of PAHs, especially under anoxic conditions. The effects of temperature on the abundance and community characteristics of indigenous bacteria in soil are also unclear. Consequently, thermally enhanced anoxic biodegradation of PAHs in subsurface soil was investigated in this study. After 150 days of anoxic incubation, both the bacterial abundance and the removal rates of PAHs in soil were positively affected by temperature. The total number of potential PAH-degrading bacteria (Proteobacteria and Firmicutes) was increased by 0.11–0.72 orders of magnitude compared to the untreated soil in different temperature treatment groups (20 °C, 30 °C, 40 °C, and 50 °C). Firmicutes was more adaptable to higher temperatures than Proteobacteria. The removal rates of total PAHs increased from 28.85% to 50.44% with increasing temperature. The degradation rates of three- and four-ring PAHs were significantly higher than those of five- and six-ring PAHs. These findings provide a more applicable and economical way to treat with PAHs contaminated subsurface soil where the temperature is lower than the target temperature needed for the desorption of PAHs from the soil when ISTD is used. 

Tengfei Zhang

Papers

Photochemical Formation and Transformation of Birnessite: Effects of Cations on Micromorphology and Crystal Structure.

Apparent digestibility of nutrients in grass carp (Ctenopharyngodon idellus) diet supplemented with graded levels of neutral phytase using pretreatment and spraying methods

Thermally enhanced anoxic biodegradation of polycyclic aromatic hydrocarbons (PAHs) in a highly contaminated aged soil

Formation and transformation of manganese(III) intermediates in the photochemical generation of manganese(IV) oxide minerals.

UV-induced highly efficient removal of As(III) through synergistic photo-oxidation in the presence of Fe(II)