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The present study was conducted to determine the digestible choline requirement of juvenile yellowtail kingfish (Seriola lalandi; YTK) in the presence of 2-amino-2-methyl-1-propanol (AMP), an inhibitor of choline biosynthesis. The second aim of this study was to determine if choline supplementation of a practical diet made from common raw materials can improve the growth performance of YTK and if choline supplementation dosages are affected by water temperature. Two eight-week experiments were conducted. The first was a dose-response experiment in which juvenile YTK (156.3 ± 15.3 g) were reared at 16 °C and fed five isonitrogenous and isoenergetic semi-purified diets containing 0.42 (Diet 1), 1.10 (Diet 2), 1.37 (Diet 3), 2.96 (Diet 4) or 6.05 g digestible choline kg−1 diet (Diet 5) by adding graded concentrations of choline chloride (CC). A sixth diet (Diet 6), comparable to Diet 4, was made without AMP to estimate the de novo synthesis of choline by YTK. The second was a factorial experiment in which juvenile YTK (157.3 ± 11.9 g) were reared at 16 °C and 24 °C and fed a practical diet supplemented with 0.0, 3.0 or 6.0 g of CC kg−1 which equates to a digestible choline concentration of 1.77, 3.54 and 4.66 g kg−1 diet, respectively. Results from experiment 1 indicated the breakpoint (broken-line regression model) in specific growth rate (SGR) and choline deposition rate occurred when digestible choline intake reached 26.1 mg kgBW−1 d−1 and 27.3 mg kgBW−1 d−1, respectively. On a dietary basis, the breakpoint in SGR and choline deposition rate occurred when diets provided 1.93 and 1.94 g digestible choline kg−1 diet, respectively. Experiment 2 results indicated there were no significant interactions between dietary choline and water temperature with respect to production indices such as SGR, food conversion ratio (FCR), whole body composition and nutrient retention. Choline deposition rate, SGR and FCR tended to be better in fish fed the practical diet supplemented with 3.0 g CC kg−1, but there was no additional advantage of raising the content to 6.0 g CC kg−1 diet. The present study confirms the necessity of adding CC to practical diets for YTK given that practical diets with no CC supplementation contain lower digestible choline than the estimated requirement established in experiment 1.

The complete replacement of fishmeal with terrestrial meals did not have a negative impact on the attractiveness, palatability, and apparent digestibility of the formulation. Shrimp were found on average to eat more and have similar appetite revival on the terrestrial meal-based formulation (TM) diet compared to the traditional fishmeal-based formulation (FM) diet. However, methionine (Met) and lysine (Lys) leached out rapidly from the TM diet, and as a result, this initially overfortified diet showed lower levels of those AA in comparison to FM after 60 min immersion. Both dietary Lys and Met were sub-optimal in TM within 120 min of immersion, whereas in comparison, the FM diet supplied consistent levels of EAA for up to 240 min immersion. Nonetheless, shrimp fed fresh TM had significantly higher peak haemolymph concentrations at 30 and 60 min for total AA, Met, and Lys than FM-fed shrimp. The over-supply of CAA far compensated leaching losses, and CAA were well absorbed and used by the shrimp within 120 min, with no obvious signs of asynchronous absorption of CAA to protein-bound AA. However, shrimp fed the TM diet that had leached out for 60 min, had haemolymph concentrations of Met and Lys that were only 41% and 44% of the ones on fresh feed respectively, while there was a negligible effect of leaching on FM. This study provides further insight into the feeding behaviour and bioavailability of dietary amino acids for P. monodon juveniles.

The apparent digestibility (AD) of dietary nutrients is an essential criterion used to improve nutrition in aquaculture. We assessed whether Near-Infrared Spectroscopy (NIRS) can assist in streamlining the process by predicting directly diet AD or the composition of diets and/or faecal nutrients and digestibility marker (yttrium oxide) concentrations collected in Yellowtail Kingfish (YTK) in vivo experiments. NIRS models were developed using up to 121 diets and 185 faecal samples, and assessed as part of a case-study investigating the accuracy of AD results for 7 validation diets using a range of prediction scenarios (S2-S5) against the benchmark analytical method (S1; all samples analysed). A large range in AD of diets was noted and results from the case-study suggested diet nutrient digestibility was significantly affected by the type of alternative ingredients used (AD dry matter ranged 45–73%; AD protein 75–85%; AD lipid 66–92%; AD energy 65–87%; AD amino acids 78–86%; AD methionine 81–90%; AD lysine 77–91%; AD taurine 70–79%). NIRS models had cross-validation R values ranging 0.63–0.89 and residual predictive deviation (RPD) values ranging 0.7–3.3 for diet nutrients; R values ranging 0.63–0.94 and RPD values ranging 1.8–4.0 for faeces. Successful NIRS models were developed for diet dry matter, ash, crude protein, total lipid, gross energy, and total amino acids; successful faeces models also included methionine and lysine but not dry matter and ash; taurine and yttrium oxide models were deemed unsuccessful for both diets and faeces. Dry matter AD based on either yttrium concentration predictions (S4) or direct prediction of diet AD (S5) were relatively inaccurate (±20% error in dry matter AD). Nonetheless S4 was relatively successful to predict lipid AD and S5 the protein AD of the seven diets with an average error of ±6.7% AD and ± 5% AD respectively compared to the benchmark. When the digestibility marker concentrations were analysed, the S2 (diet composition predicted) and S3 (diet and faeces composition predicted) scenarios could predict nutrient AD with a degree of error of ±1–3%, with the exception of lipid AD (±6–8% error), and taurine which was modelled poorly in this study. NIRS prediction of diet and faecal composition, combined with digestibility marker analysis, appears to be a cost-effective and reasonably accurate rapid method to assess diet AD in fish, reducing sample volume requirements, welfare impact and opening a range of new opportunities for fish nutrition and the development of more efficient phenotypes.

Macrocyclic lactone (ML) drugs inhibit pharyngeal pumping, motility and egg laying in parasitic nematodes. Previous work has indicated that in vitro effects on worm feeding occurred at lower ivermectin concentrations than effects on worm motility, suggesting that the pharynx musculature was a more important target site for the ML drugs than somatic musculature. We have reassessed this issue of relative sensitivity by examining the response of drug-susceptible and -resistant adult Haemonchus contortus worms to abamectin in vitro using both feeding and motility assays. The motility assay involved observation of changes in the form and degree of movement of individual worms in response to the drug. A comparison of the data from the two assays indicated that worm motility was affected at drug concentrations below those required to inhibit feeding. Analysis of the motility data using different levels of sensitivity (varying in the degree to which they accounted for subtle vs. more profound changes in worm motility) provided an explanation as to why earlier reports had observed feeding to be the more sensitive target. Motility IC50 values shifted from being less than feeding IC50s to being greater than the feeding IC50s as the motility assay analysis method became less sensitive. The present study indicates that when sensitive worm motility assessment methods are utilised, worm motility is affected at lower abamectin concentrations than worm feeding, and hence highlights somatic musculature as a more important target site for this ML drug, and most likely for ML drugs in general.

Waste generated from the processing of marine organisms for food represents an underutilized resource that has the potential to provide bioactive molecules with pharmaceutical applications. Some of these molecules have known anti-thrombotic and anti-coagulant activities and are being investigated as alternatives to common anti-thrombotic drugs, like heparin and warfarin that have serious side effects. In the current study, extracts prepared from blacklip abalone (Haliotis rubra) processing waste, using food grade enzymes papain and bromelain, were found to contain sulphated polysaccharide with anti-thrombotic activity. Extracts were found to be enriched with sulphated polysaccharides and assessed for anti-thrombotic activity in vitro through heparin cofactor-II (HCII)-mediated inhibition of thrombin. More than 60% thrombin inhibition was observed in response to 100 μg/mL sulphated polysaccharides. Anti-thrombotic potential was further assessed as anti-coagulant activity in plasma and blood, using prothrombin time (PT), activated partial thromboplastin time (aPTT), and thromboelastography (TEG). All abalone extracts had significant activity compared with saline control. Anion exchange chromatography was used to separate extracts into fractions with enhanced anti-thrombotic activity, improving HCII-mediated thrombin inhibition, PT and aPTT almost 2-fold. Overall this study identifies an alternative source of anti-thrombotic molecules that can be easily processed offering alternatives to current anti-thrombotic agents like heparin.

Histone deacetylase inhibitors (HDACi) are being investigated for the control of various human parasites. Here we investigate their potential as insecticides for the control of a major ecto-parasite of sheep, the Australian sheep blowfly, Lucilia cuprina. We assessed the ability of HDACi from various chemical classes to inhibit the development of blowfly larvae in vitro, and to inhibit HDAC activity in nuclear protein extracts prepared from blowfly eggs. The HDACi prodrug romidepsin, a cyclic depsipeptide that forms a thiolate, was the most potent inhibitor of larval growth, with equivalent or greater potency than three commercial blowfly insecticides. Other HDACi with potent activity were hydroxamic acids (trichostatin, CUDC-907, AR-42), a thioester (KD5170), a disulphide (Psammaplin A), and a cyclic tetrapeptide bearing a ketone (apicidin). On the other hand, no insecticidal activity was observed for certain other hydroxamic acids, fatty acids, and the sesquiterpene lactone parthenolide. The structural diversity of the 31 hydroxamic acids examined here revealed some structural requirements for insecticidal activity; for example, among compounds with flexible linear zinc-binding extensions, greater potency was observed in the presence of branched capping groups that likely make multiple interactions with the blowfly HDAC enzymes. The insecticidal activity correlated with inhibition of HDAC activity in blowfly nuclear protein extracts, indicating that the toxicity was most likely due to inhibition of HDAC enzymes in the blowfly larvae. The inhibitor potencies against blowfly larvae are different from inhibition of human HDACs, suggesting some selectivity for human over blowfly HDACs, and a potential for developing compounds with the inverse selectivity. In summary, these novel findings support blowfly HDAC enzymes as new targets for blowfly control, and point to development of HDAC inhibitors as a promising new class of insecticides., Graphical abstract Image 1, Highlights • We measured the insecticidal effects of histone deacetylase inhibitors against the sheep blowfly. • Insecticidal activity correlated with inhibition of HDAC enzyme activity in nuclear extracts. • Romidepsin showed equivalent or greater potency than commercial blowfly insecticides. • Some insights gained into structural requirements for insecticidal HDAC inhibitors. • Potential for HDAC inhibitors as insecticides.

Background The acute response to genotoxic carcinogens in rats is an important model for researching cancer initiation events. In this report we define the normal rat colonic epithelium by describing transcriptional events along the anterior-posterior axis and then investigate the acute effects of azoxymethane (AOM) on gene expression, with a particular emphasis on pathways associated with the maintenance of genomic integrity in the proximal and distal compartments using whole genome expression microarrays. Results There are large transcriptional changes that occur in epithelial gene expression along the anterior-posterior axis of the normal healthy rat colon. AOM administration superimposes substantial changes on these basal gene expression patterns in both the distal and proximal rat colonic epithelium. In particular, the pathways associated with cell cycle and DNA damage and repair processes appear to be disrupted in favour of apoptosis. Conclusions The healthy rats’ colon exhibits extensive gene expression changes between its proximal and distal ends. The most common changes are associated with metabolism, but more subtle expression changes in genes involved in genomic homeostasis are also evident. These latter changes presumably protect and maintain a healthy colonic epithelium against incidental dietary and environmental insults. AOM induces substantial changes in gene expression, resulting in an early switch in the cell cycle process, involving p53 signalling, towards cell cycle arrest leading to the more effective process of apoptosis to counteract this genotoxic insult.