Experimental susceptibility of Atlantic cod, Gadus morhua (L.), and Atlantic halibut, Hippoglossus hippoglossus (L.), to different genotypes of viral haemorrhagic septicaemia virus

Viral haemorrhagic septicaemia (VHS) is a well-characterized disease of rainbow trout, Oncorhynchus mykiss, which has also caused economic losses in marine turbot farms in the British Isles. We have previously demonstrated that turbot, Scophthalmus maximus, are susceptible to isolates of viral haemorrhagic septicaemia virus (VHSV) that are endemic in the marine environment, highlighting a potential risk to marine aquaculture. Given the increasing interest in the intensive rearing of additional aquaculture species such as Atlantic cod, Gadus morhua, and Atlantic halibut, Hippoglossus hippoglossus, this study aimed at investigating the susceptibility of these species to VHSV. Both species were found to be largely resistant to VHS following immersion challenge with a selection of 18 isolates, representing the known marine VHSV genotypes. Only one and two VHSV-associated mortalities occurred out of a total of 1710 and 1254 halibut and cod, respectively. These findings suggest that there is a low direct risk to the development of commercial cod and halibut aquaculture from the existing endemic reservoir of VHSV. This study, coupled to field observations has, however, highlighted the fact that both species can become infected with VHSV. The known adaptability of RNA viruses, together with the selection pressures associated with intensive aquaculture would thus advocate a cautious approach to VHSV surveillance within these emerging industries.     

Effects of dbcAMP on steroidogenesis in isolated ovarian follicles of Atlantic salmon

In vitro estradiol-17β (E₂) and testosterone (T) production were measured in vitellogenic follicles of Atlantic salmon in response to treatment with human chorionic gonadotropin (hCG) and 2-0-dibutyryladenosine 3′,5′-cyclic monophosphate (dbcAMP). DbcAMP stimulated T production but had no effect on E₂, whereas hCG treatment stimulated E₂ production but T production was low. Elevated intracellular [cAMP] may be part of the normal mechanism for inhibition of aromatase activity at the end of vitellogenesis.     

Evaluating changes in switchgrass physiology,biomass, and light-use efficiency under artificial shade to estimate yields if intercropped with Pinus taeda L.

There is growing interest in using switchgrass (Panicum virgatum L.) as a biofuel intercrop in forestry systems. However, there are limited data on the longevity of intercropped bioenergy crops, particularly with respect to light availability as the overstory tree canopy matures. Therefore, we conducted a greenhouse study to determine the effects of shading on switchgrass growth. Four treatments, each with different photosynthetically active radiation (PAR) levels, were investigated inside the greenhouse: control (no shade cloth, 49 % of full sunlight), low (under 36 % shade cloth), medium (under 52 % shade cloth), and heavy shade (under 78 % shade cloth). We determined the effect of shading from March to October 2011 on individually potted, multi-tillered switchgrass transplants cut to a stubble height of 10 cm. In the greenhouse, there was a reduction in tiller number, tiller height, gas exchange rates (photosynthesis and stomatal conductance), leaf area, above- and belowground biomass and light-use efficiency with increasing shade. Total (above- and belowground) biomass in the control measured 374 ± 22 compared to 9 ± 2 g pot^?1 under heavy shade (11 % of full sunlight). Corresponding light-use efficiencies were 3.7 ± 0.2 and 1.4 ± 0.2 g MJ^?1, respectively. We also compared PAR levels and associated aboveground switchgrass biomass from inside the greenhouse to PAR levels in the inter-row regions of a range of loblolly pine (Pinus taeda L.) stands from across the southeastern United States (U.S.) to estimate when light may limit the growth of intercropped species under field conditions. Results from the light environment of loblolly pine plantations in the field suggest that switchgrass biomass will be significantly reduced at a loblolly pine leaf area index between 1.95 and 2.25, which occurs on average between ages 6 and 8 years across the U.S. Southeast in intensively managed pine plantations. These leaf area indices correspond to a 60–65 % reduction in PAR from open sky.     

Phosphorus utilization in rainbow trout (Oncorhynchus mykiss) fed practical diets and its consequences on effluent phosphorus levels

Excessive dietary phosphorous (P) concentrations in effluents from aquaculture present a major environmental problem. We therefore studied the effect of dietary P and vitamin D₃ on P utilization by rainbow trout-fed practical diets and on P concentrations in the soluble, particulate and settleable components of the effluent from fish tanks. Rainbow trout (average weight: 78 g, initial biomass: 13 kg in 0.7 m³ tanks) were fed for 11 weeks, practical diets that varied in total P, available P, and vitamin D₃ concentrations. Soluble, particulate (10–200 μm) and settleable (>200 μm) P in the effluent were sampled every 0.5–6 h for 1–3 days in the third and eleventh weeks of the experiment. Trout in all diets more than doubled their weight after 11 weeks. Increasing the concentrations of available dietary P from 0.24% to 0.88% modestly enhanced growth rate. Feed conversion ratio (FCR) and biomass gain per gram P consumed decreased as dietary P concentrations increased. Carcass P, daily P gain, and plasma P concentrations were lower in fish fed with low P diets. Soluble P concentrations in the effluent peaked immediately after and again 4–6 h after feeding, and is a linear function of available dietary P. No soluble P would be produced during consumption of diets containing less than 0.22±0.02% available P. Above this dietary concentration, soluble P would be excreted at 6.9±0.4 mg/day/kg for each 0.1% increase in available dietary P. Particulate P concentrations in the effluent were independent of dietary P concentrations. Settleable, presumably fecal, P concentrations tended to increase with dietary P concentrations. In trout fed with low P (0.24% available P, 0.6% total P) diets, 60% of total dietary P were retained by the fish and the remaining 40% were excreted in the effluent as settleable P (20–30%) and particulate or soluble P (10–20%). In trout fed with high P (0.59–0.88% available P; 0.9–1.2% total P) diets, 30–55% of total dietary P was retained by fish, and the remaining 15–25% appeared in the effluent as settleable P, 20–55% as soluble P, and 5–10% as particulate P. Vitamin D₃ did not affect fish growth nor effluent P levels. Physicochemical management of aquaculture effluents should consider the effect of diets on partitioning of effluent P, the peaks of soluble P concentration following feeding, and the contributions of particulate P to total P in the effluent. Increasing our understanding of how dietary P is utilized and is subsequently partitioned in the effluent can contribute significantly towards alleviating this important environmental and industry problem.     

Larval and juvenile Australian smelt Retropinna semoni somatic and otolith growth parameters – implications for growth interpretation of wild fish

Abstract –  Relationships between fish length, otolith size, age and weight were assessed for a population of wild Australian smelt ( Retropinna semoni ) larvae and juveniles captured over a 4-year period to aid further interpretation of growth and condition during the early life history of the species. Nonlinear smoothed generalized additive models best described the fish–otolith size relationship during the larval and juvenile period, indicating that the proportionality between fish length and otolith size varies in relation to size. It is proposed that back-calculated predictions of fish size at a previous age or otolith size, accounting for individual variation is possible by assuming a body proportional hypothesis. Growth rate of larval and juvenile Australian smelt was best described using the Gompertz model that indicated a steady decline in growth rate after around 30 days of age. The allometric growth of larval and juvenile Australian smelt established from the length/weight relationship can subsequently be used to assess the condition of fish within this population using a relative condition or relative weight condition index. The results of the study have provided significant information to enable more precise growth reconstruction and condition assessment for the species in Australian lowland rivers.     

Field trial of a staphylococcal mastitis vaccine in dairy herds: clinical, subclinical and microbiological assessments

Objective To assess the efficacy of a new staphylococcal mastitis vaccine under commercial dairying conditions.
Design A field trial involving 1819 cows and heifers conducted on seven dairy herds in Victoria. The trial was done 'blind'; approximately half the animals were vaccinated and the remainder were untreated controls.
Procedure The vaccine was given twice during the last 10 weeks of pregnancy. Effects of vaccination were assessed, during the ensuing lactation, on the basis of clinical and sub-clinical mastitis and microbiological investigations of the milk.
Results A total of 273 cases of clinical mastitis were recorded. Staphylococcus aureus was isolated from 112 of these, 45 cases in vaccinates and 67 cases in controls; the difference was not statistically significant. One herd was notable in having a high incidence of clinical staphylococcal mastitis. This herd accounted for 15.8% of the animals in the field trial but 54.5% of cases of clinical staphylococcal mastitis. For this herd, vaccinated animals had significantly lower incidence of clinical staphylococcal mastitis and prevalence of subclinical mastitis, relative to controls. An unexpected feature of the trial as a whole was the low incidence of clinical mastitis from which S aureus was isolated in pure culture (26.3% of cases) and the high incidence of clinical Streptococcus uberis mastitis (22.7% of cases).
Conclusions The trial showed that the vaccine was efficacious in reducing the incidence of clinical mastitis and prevalence of subclinical mastitis in a herd that had a serious staphylococcal mastitis problem.     

Embryonic development in the blue fox

Embryos from vixens at different stages of gestation were measured and photographed. Implantation was observed 16-18 days after breeding. Differentiation and the development of characteristic features were described and embryonic loss was studied in relation to number of corpora lutea.     

Amoebic meningoencephalitis caused by Balamuthia mandrillaris in an orang utan

Objective
To describe a case of meningoencephalitis caused by Balamuthia mandrillaris in an orang utan.
Design
A pathological case report.
Animal
A 20 years old male orang utan (Pongo pygmaeus).
Procedure
The disease process was investigated by clinical pathology, necropsy, histopathology and immunofluorescence labelling.
Results
The orang utan developed sudden onset of depression, lethargy, inappetence and apparent head pain. The condition was considered to be related to a 2 year history of upper and lower respiratory disease, and the animal was placed on antibiotics after extensive testing. By the seventh day the animal had become ataxic and disoriented and a brain abscess was suspected. He died on the ninth day of illness. At necropsy, and subsequent sectioning, the brain showed multiple circular, soft, white to grey brown areas of varying size, the largest being in the left temporal (3.5 cm diameter) and right occipital (2.5 cm diameter) regions of the cerebrum. Histological examination of these regions revealed many amoebic trophozoites and occasional cysts associated with areas of haemorrhage and inflammatory necrosis. The trophozoites were packed in perivascular spaces and their nuclei often contained two or more prominent nucleoli. Immunofluorescent labelling of histological sections suggested that the agent was B mandrillaris.
Clinical implications
This report provides further evidence that B mandrillaris , a free living amoeba, can act as a pathogen in animals as well as people, and cause fatal meningoencephalitis. Along with Naegleria and Acanthamoeba spp, B mandrillaris should be considered amongst the causes of acute onset meningoencephalitis in animals.     

Evaluation of maternal parent and puroindoline allele on kernel texture in a reciprocal cross between two hard spring wheat cultivars

Kernel texture is an important characteristic for both the milling and the end-use quality of wheat (Triticum aestivum L.). Gene sequence variation and mutations to the two puroindoline genes (Pina and Pinb), located at the Ha locus on chromosome 5DS, account for the majority of variation in wheat kernel texture. Other factors also influence kernel texture, including effects associated with different maternal parent backgrounds. To investigate the effect of two hard puroindoline alleles in different maternal backgrounds, a population of 228 recombinant inbred lines (RILs) derived from a reciprocal cross between two wheat cultivars ID377s (Pina-D1b/Pinb-D1a) and Klasic (Pina-D1a/Pinb-D1b) were examined in two succeeding generations (F₇ & F₈). Kernel texture was determined using the Single Kernel Characterization System (SKCS) and the RIL puroindoline haplotype was identified by the sequence-specific PCR amplification of each gene. Analysis of variance identified a significant (P 0.001) effect of the maternal parent and puroindoline mutation on kernel texture. RILs containing the Pina-D1b mutation were significantly harder than lines containing the Pinb-D1b mutation. RILs which had Klasic as the maternal parent were significantly harder than those which had ID377s as the maternal parent. When the maternal parent and puroindoline allele were analyzed in combination, RILs derived from Klasic as the maternal parent and the Pina-D1b allele were significantly harder (P 0.001) than those containing the same allele but ID377s as the maternal parent. The same occurred for RILs containing the Pinb-D1b allele, lines with Klasic as the maternal parent were harder than lines with ID377s as the maternal parent. These results corroborate the harder phenotype of the Pina-D1b allele and indicate a significant maternally-inherited contribution to kernel texture variation.