Intake and discharge nutrient loads at three intensive shrimp farms

This study was conducted to help provide a framework for Australian regulation of shrimp farm siting and discharges. Monitoring of farm water usage, and intake and discharge water quality was conducted at three commercial intensive shrimp farms, chosen to represent different operating environments, latitudes, cultured species and management styles. Weekly samples were taken over 3 years, for 3–12 months at each farm, to investigate intake and discharge concentrations and loads of total suspended solids (TSS), total nitrogen (TN) and total phosphorus (TP). Mean water exchange was 1.4 ML ha^?1 day^?1 (about 10% day^?1) at the first farm studied and 0.5 ML ha^?1 day^?1 (about 3.6% day^?1) at the others. Farm mean discharge concentration varied as follows: TSS, from 36.9 to 119 mg L^?1; TN, from 2.1 to 3.1 mg L^?1 and TP, from 0.22 to 0.28 mg L^?1. Farm mean intake concentrations were from 11% to 91% of equivalent mean discharge concentration (for TN at Farm B and TSS at Farm C respectively). Mean net discharge loads, related to area of production ponds at each farm, varied as follows: TSS, from 4.8 to 85.7 kg ha^?1 day^?1; TN, from 1 to 1.8 kg ha^?1 day^?1 and TP, from 0.11 to 0.22 kg ha^?1 day^?1. The highest net loads of TSS, TN and TP were all from the farm with the highest water exchange rate, located on a coastal river, and studied during a year of high rainfall with associated poor water quality. These results can be used to help predict likely discharge characteristics for new shrimp farms, and provide a benchmark against which to evaluate future improvements in shrimp farm environmental management.     

In vitro effects of DDT analogs on trout brain Mg2+-ATPases: Inhibition kinetics

A continuous in vitro steady-state assay procedure was used to investigate the dependence of trout brain mitochondrial Mg²⁺-stimulated adenosinetriphosphatase specific activity on temperature and substrate concentration. The inhibition of enzyme activity by DDT was independent of substrate concentration. DDT and several analogs caused increases in the experimental activation energy and frequency factor of the enzyme-catalyzed reaction, which gave rise to a negative temperature coefficient of inhibition. It is suggested that DDT and other highly lipophilic compounds have the potential to allosterically affect membrane-bound enzymes by simply becoming a major lipoid component of the membranes.     

Evaluation of the effectiveness of Duddingtonia flagrans and Monacrosporium thaumasium in the biological control of gastrointestinal nematodes in female bovines bred in the semiarid region

Brazil has a herd of 212 million cattle and 171 million hectares of pastures that produce approximately 96 % of Brazilian beef. The Brazilian production system enables animal infection by endoparasites, which are considered one of the main obstacles for the development of this industry and are responsible for considerable economic losses. The control of parasitic diseases is performed via the administration of antiparasitic drugs, but they leave residues of the products in the treated animal, affect non-target organisms and select resistant strains of the parasites. The species D. flagrans and M. thaumasium are promising and sustainable alternatives for controlling gastrointestinal helminths of ruminants and other herbivores. In this study, we evaluated the efficacy of isolates of these species, formulated in a sodium alginate matrix and administered twice a week, to reduce the number of environmental infective larvae of gastrointestinal nematodes that affect prepubescent zebu females. The treated animals presented fewer eggs and a lower number of infective larvae per gram of faeces (p?<?0.05). The pastures occupied by treated animals showed a statistically significant reduction (p?<?0.05) of the number of L₃ and, furthermore, the genera Cooperia sp., Haemonchus sp., and Oesophagostomum sp. were the most prevalent. The average weight of the animals did not differ statistically (p?>?0.05) among the treated and control groups. The use of sodium alginate pellets as vehicle for delivery of the fungus mycelia D. flagrans (isolate AC001) and M. thaumasium (isolate NF34A) proved effective in controlling trichostrongylids in prepubescent cows bred in the semi-arid region, with an effective reduction in the number of infective larvae in the pastures.     

Pseudomonas syringae pv. coryli, the Causal Agent of Bacterial Twig Dieback of Corylus avellana

ABSTRACT Thirty-eight bacterial strains isolated from hazelnut (Corylus avellana) cv. Tonda Gentile delle Langhe showing a twig dieback in Piedmont and Sardinia, Italy, were studied by a polyphasic approach. All strains were assessed by fatty acids analysis and repetitive sequence-based polymerase chain reaction (PCR) fingerprinting using BOX and ERIC primer sets. Representative strains also were assessed by sequencing the 16S rDNA and hrpL genes, determining the presence of the syrB gene, testing their biochemical and nutritional characteristics, and determining their pathogenicity to hazelnut and other plants species or plant organs. Moreover, they were compared with reference strains of other phytopathogenic pseudomonads. The strains from hazelnut belong to Pseudomonas syringae (sensu latu), LOPAT group Ia. Both fatty acids and repetitive-sequence-based PCR clearly discriminate such strains from other Pseudomonas spp., including P. avellanae and other P. syringae pathovars as well as P. syringae pv. syringae strains from hazelnut. Also, the sequencing of 16S rDNA and hrpL genes differentiated them from P. avellanae and from P. syringae pv. syringae. They did not possess the syrB gene. Some nutritional tests also differentiated them from related P. syringae pathovars. Upon artificial inoculation, these strains incited severe twig diebacks only on hazelnut. Our results justify the creation of a new pathovar because the strains from hazelnut constitute a homogeneous group and a discrete phenon. The name of P. syringae pv. coryli is proposed and criteria for routine identification are presented.     

Drug sales and the veterinarian

Sir,—Most private practitioners and probably all veterinary clubs in New Zealand derive a considerable portion of their incomes from the sales of drugs, and it is certainly true that most veterinary dubs are dependent on drug sales profits to allow them to continue at their present economic levels.     

Machine learning highlights the importance of primary and secondary production in determining habitat for marine fish and macroinvertebrates

1. Species distribution models for marine organisms are increasingly used for a range of applications, including spatial planning, conservation, and fisheries management. These models have been constructed using a variety of mathematical forms and drawing on both physical and biological independent variables; however, what might be called first-generation models have mainly followed the form of linear models, or smoothing splines, informed by data collected in the context of fish surveys.
2. The performance of different classes of variables were tested in a series of species occurrence models built with machine learning methods, specifically evaluating the potential contribution of lower trophic level data. Random forest models were fitted based on the classification of the absence/presence for fish and macroinvertebrates surveyed on the US Northeast Continental Shelf.
3. The potential variables included physical, primary production, secondary production, and terrain variables. For accepted model fits, six variable importance measures were computed, which collectively showed that physical and secondary production variables make the greatest contribution across all models. In contrast, terrain variables made the least contribution to these models.
4. Multivariable analyses that account for all performance measures reinforce the role of water depth and temperature in defining species presence and absence; however, chlorophyll concentration and some specific zooplankton taxa, such as Metridia lucens and Paracalanus parvus, also make important contributions with strong seasonal variations.
5. Our results suggest that lower trophic level variables, if available, are valuable in the creation of species distribution models for marine organisms.

     

Detection and measurement of benzimidazole resistance alleles in Haemonchus contortus using real-time PCR with locked nucleic acid Taqman probes

Benzimidazole resistance is a common problem in parasitic nematodes of ruminants and early detection is vital if its spread is to be monitored and controlled. Real time PCR offers a fast and reliable method for rapid detection and measurement of resistance allele frequencies. In Haemonchus contortus a single nucleotide polymorphism at codon 200 of the beta-tubulin gene (TTC to TAC), causing a phenylalanine to tyrosine amino acid substitution, has been shown to be involved in many cases of resistance. Locked nucleic acid (LNA) Taqman probes have been used in this work to detect and measure the frequency of resistance alleles in individual and multiple H. contortus. Detection of resistant genotypes using LNA Taqman probes in individual H. contortus is simpler and more reliable than with previously described assays. Measurement of the frequency of resistant alleles in populations of H. contortus was achieved by using the cycle threshold (C(t)) values and a standard curve derived from populations with known allele frequencies. Results using the LNA probes on individual and multiple worms gave similar results to the allele specific PCR. The sensitivity of the LNA assay on multiple nematodes allowed reliable detection of > or = 10% resistance allele frequency. Using the final fluorescence method, it was possible to differentiate populations with approximately 0, 5 and 10% resistance allele frequencies.