ABSTRACT:
Commercial channel catfish (Ictalurus punctatus) is an economically valuable agricultural commodity in the United States, which suffers heavily from bacterial pathogens including Edwardsiella ictaluri. Our previous study revealed that dietary trans-cinnamaldehyde (TC) reduces catfish mortality after E. ictaluri infection, but there is limited knowledge of the effect of TC on the antioxidant defense system in catfish. In this study, we aimed to investigate the response of the catfish antioxidant defense system following TC feeding as well as E. ictaluri infection. In the first experiment, catfish fingerlings were fed with a basal diet or a basal diet supplemented with TC (20 mg/kg diet) for 10 days, and the level of five oxidative stress biomarkers were measured in the hepatic tissue. Compared with the control group, superoxide dismutase (SOD) activity was increased significantly and the malondialdehyde (MDA) concentration decreased significantly (P < 0.001) in hepatic tissue of catfish that were fed a TC-supplemented diet. Whereas activities of catalase (CAT) and reduced glutathione (GSH) as well as nitric oxide (NO) concentration did not show significant differences between TC and control groups. In the second experiment, catfish fingerlings were fed a TC-supplemented or normal diet followed by infection with E. ictaluri, and the activities of oxidative biomarkers were measured on 1, 6, and 14-days post-infection (dpi). Significant (P < 0.001) increases in CAT, SOD, and GSH activities were observed in catfish fed TC when compared with those fish fed a normal diet on 1, 6, and 14 dpi. A significant (P < 0.001) decrease in NO and MDA concentrations were found in catfish that received a TC diet compared to the control group at 1, 6, and 14 dpi. In conclusion, dietary TC improved the oxidative stress response in catfish following E. ictaluri challenge. These results provide information regarding the mechanisms by which TC provides protection against E. ictaluri infection.© 2020 Elsevier B.V.

ABSTRACT:
Aquaculture diversification is important for providing sustainable sources of food fish amidst changing environments, pathogens, economies, and market demand. Particularly for newly cultured species where information may be limited, optimization of culture practices relies on an understanding of the physiology and ecology of a species. The cojinoba (Seriolella violacea; Centrolophidae), a coastal pelagic marine fish, is a species of growing importance for aquaculture production in South America. Although methods for breeding and larval to juvenile rearing have been established, little is known about the physiology of this species. Therefore, measures of metabolism, swimming capacity and efficiency, red:white (R:W) muscle ratios, and associated aerobic and anaerobic biochemical parameters, such as plasma glucose and lactate, and muscle enzyme activities (i.e., pyruvate kinase, citrate synthase, electron transport system [ETS]), were measured. For cojinoba at 15 °C with mean body length (BL; total length) of 22 cm, critical swimming velocity (Ucrit) was approximately 80 cm/s or 3.8 BL/s, and optimal swimming velocity (Uopt) was 50 cm/s or 2.3 BL/s. Aerobic scope for metabolism was approximately 300 mg O2/kg/h, with Mo2 max 3.4 fold greater than standard metabolic rate. Swimming was facilitated by linear increases in tail beat frequency until burst and glide swimming initiated near Ucrit. At low velocities, large (~20% BL) pectoral fins were used for propulsion and maneuverability/maintaining equilibrium; beat frequency diminished rapidly with increasing velocity. Red:white muscle ratios at 50% BL and 75% BL (caudal peduncle) were comparable to other ectothermic species, with a greater proportion of red muscle in the caudal peduncle presumably corresponding to facilitation of sustained pelagic swimming. Plasma glucose and lactate were elevated at Ucrit by 20% and 45% respectively, indicating mobilization of anaerobic energy sources at fatigue. Aerobic enzyme activities were much higher in red muscle, the ratio of anaerobic:aerobic enzyme activity was higher in white muscle, and ETS activities decreased at fatigue in both red and white muscle. The cojinoba has a moderate metabolic rate compared to other pelagic species, displays shoaling behavior, is maneuverable at low velocities due to pectoral fin use, but has optimal swimming efficiencies at higher velocities. These factors are beneficial for designing culture systems to promote exercise benefits for growth and welfare. © 2020 Elsevier B.V.

ABSTRACT:
A strain of atypical Aeromonas hydrophila (aAh) has caused issues within the channel catfish Ictalurus punctatus industry of the southeastern United States since 2009. These atypical pathotypes cause acute mortality events resulting in catastrophic losses, as opposed to more chronic mortality and lesions seen in typical infections of motile aeromonas septicemia (MAS). This study provides a basic framework for rapid field sampling negating the need for re-isolation or enrichment culture, thereby reducing the time between sampling and detection. Rapid and accurate quantitative PCR based methods for detection of aAh have been described and are important confirmative tools in research and diagnostic settings. These methods also have application in epidemiological surveys investigating the spread of disease and elucidating pathogen dynamics that may lead to outbreaks. To date, no field-based sampling technique for rapid aAh detection in resident pond populations has been explored. In this study, culture swabs taken from the gills and lower intestine of pond-raised catfish were assessed for their suitability as rapid field-based collection methods for downstream applications. Results showed the state of the pond has a significant effect on which swab location yields the highest proportion of PCR positive results. During an active outbreak, gill swabs identified more fish as aAh-positive; however, in apparently healthy populations, swabs taken from the lower intestine identified significantly more aAh-positive fish than gill swabs, despite no statistical difference in the concentration of aAh cell equivalents between swab sites. Naïve prevalence estimates from the two swab types were compared to estimates provided by a hierarchical occupancy model. Prevalence estimates from gill swabs was 0.95% while vent swabs showed a prevalence of 2.2%; however, estimates based on the occupancy model were 6.6% and 9.8%, respectively. This multi-fold increase in prevalence estimates highlights the importance of accounting for imperfect detection in epidemiological studies and in assessing potential outbreak risk. Furthermore, occupancy models based on these data indicate resident fish can be aAh-positive carriers with no gross signs of infection, providing evidence aAh can reside in catfish ponds in the absence of disease. The presence of a carrier state indicates the pathogen may pose minimal risk to the host is compromised or a mechanical portal of entry into the blood stream is available. This provides an important direction for future research in understanding the mechanisms of aAh outbreaks in catfish aquaculture ponds. © 2020

ABSTRACT:
Soymilk yoghurt is an option to consumers who are allergic to cow's milk yoghurt. Probiotics can provide gut health. The objective of this study was to investigate the physicochemical characteristics, including pH, colour, firmness and syneresis of yoghurt made from soymilk and cow's milk as affected by the addition of probiotics during storage at 4 °C for 28 days at 7-day intervals. Microstructure and bacterial populations were also determined. Two types of yoghurt were prepared. The first type was prepared with the additions of commercially available yogurt starter containing Lactobacillus delbrueckii ssp. bulgaricus (LB) and Streptococcus thermophilus (ST). The second type was prepared with the same yogurt starters plus three probiotics, including Bifidobacterium animalis subsp. lactis BB-12 (BB), L. acidophilus La-5 (LA), and L. rhamnosus (LGG). Probiotics reduced syneresis and increased compact network of soymilk yoghurt significantly (p < 0.05) and shortened the time needed to reach pH 4.5 in both cow's milk and soymilk yogurts. During storage, the pH of cow's milk yoghurts slightly decreased (4.37–4.26 with probiotics and 4.54 to 4.33 without probiotics), however, the pH of soymilk yoghurts remained relatively constant. The firmness of yoghurt made from cow's milk was significantly decreased with the addition of probiotics, however, it remained stable in soy milk yoghurt during storage. Soymilk yoghurt (34–50 g force during compression) was generally firmer than cow's milk yoghurts (9.8–12.5 g force). The cow's milk yogurt had slightly higher counts of ST, LB and LA than soymilk yogurt, but the count of BB in soymilk yogurt is significantly higher than that in cow's milk yogurt. © 2020 Elsevier Ltd

ABSTRACT:
Porous structure design is considered to be a promising strategy for the development of effective sorbents for CO2 capture. Herein, a series of carbon nanoflakes with large surface area (up to 2380 m2/g) and high micropore volume (up to 0.896 m3/g) were synthesized from a renewable precursor, cork dust waste, to capture CO2 at atmospheric pressure. The nanoflakes exhibited superior CO2 uptake performance at 1 bar with the maximum capacity of 7.82 and 4.27 mmol/g at 0 and 25 °C, respectively, in sharp contrast to previously reported porous carbon materials. The existence of large numbers of narrow micropores with the pore width less than 0.86 nm and 0.70 nm play a critical role in the CO2 uptake at 0 and 25 °C, respectively. Moreover, the CNFs exhibited good recyclability and high selectivity for CO2 uptake from the mixture of CO2 and N2. By taking advantage of the unique hollow honeycomb cell, the three-layered cell wall structure, as well as the unique chemical composition of a cork precursor, such delicate microporous carbon nanoflakes were able to be achieved by simple thermal pretreatment combined with chemical activation. This bioinspired precursor-synthesis route poses a great potential for the facile production of porous carbons for a variety of diverse applications including CO2 capture. © 2020 Elsevier B.V.