Effects of Feed Application Rates on Growth, Survival, and Feed Conversion of Juvenile Snakehead Channa striatus

Growth, survival and feed conversion ratio of juvenile snakehead Channa striatus were evaluated when fed a dry, formulated feed (50% crude protein) at 24 ± 1 C. Six daily feed application rates were used (0%, 5%, 10%, 15%, 20%, and 30%), as a percentage of fish body weight, with three replicates per treatment. After 29 d, final weights were all significantly greater ( P < 0.01) than initial weights, except for the 0% application. Feed applications higher than 5% did not result in increased growth ( P > 0.05). Feed conversion ratio was 0.99 at 5% feed application, and 6.3 at 30% feed application. Fish survival was increased by providing formulated diet, but no further improvement was found when feed applications exceeded 5%. Cannibalism was reduced by providing formulated feed, but it was unavoidable when substantial differences in fish size existed, even when feeding ad libitum . Our results indicate that the optimal feed application rate is close to 5% body weight/d for juvenile snakehead.     

Effects of Broodstock Size and Source on Ovarian Maturation and Spawning of Penaeus monodon Fabricius from the Gulf of Thailand

The effects of broodstock source (pond-reared and wildcaught from shallow waters) and prawn size (large—weight >120 g, and small-weight < 110 g) on ovarian maturation and reproductive success of Penueus monodon were evaluated. Large females underwent stage IV ovarian maturation and spawned with greater success than did small prawns. Both pond-reared and wildcaught females of the same size exhibited comparable maturation and spawning success. Large females rematured and spawned more frequently than small ones. Total eggs produced by large prawns was significantly greater than for small prawns; nevertheless, prawn source and size had no significant influence on amount of eggs spawned per spawning event. Egg quality varied greatly in terms of percent fertilization, hatch rate, and metamorphosis to first protozwa stage.     

Influence of reduced feed ration on Lepeophtheirus salmonis infestation and inflammatory gene expression in juvenile pink salmon

The effect of reduced feed ration on infestation levels with the sea louse Lepeophtheirus salmonis and gene expression in juvenile pink salmon Oncorhynchus gorbuscha was tested in three laboratory trials. Body weight was significantly lower among fish on the reduced ration for 27, 34, or 65 d than fish on the full ration. Neither the prevalence nor the abundance of L. salmonis differed between fish on full and reduced rations at any time in any trial. In trial 2, sea louse rejection was delayed among fish on reduced rations; however, the parasite was ultimately rejected from all fish in this trial regardless of ration. Proinflammatory gene expression in salmon exposed to L. salmonis was modulated by reduced rations. There was a reduction in the expression of interleukin-8 in pink salmon on reduced rations 7 d after exposure but not 14 d after exposure. In contrast, the 7-d expression of interleukin-1 beta (IL-1beta) was reduced in exposed pink salmon regardless of ration. By day 14, however, expression of IL-1beta was increased in association with reduced rations among exposed salmon. Similarly, the expression of tumor necrosis factor alpha (TNFalpha) was increased 14 d after exposure among salmon on a reduced ration. There was no evidence that short-duration exposure of otherwise healthy juvenile pink salmon to a reduced ration affected susceptibility to L. salmonis. The expression data do not suggest an obvious mechanism of louse rejection; rather, they indicate that a more comprehensive suite of inflammatory pathways should be surveyed to better understand the early pink salmon response to L. salmonis.     

DNA vaccines encoding the envelope protein of West Nile virus lineages 1 or 2 administered intramuscularly,via electroporation and with recombinant virus protein induce partial protection in large falcons (Falco spp.)

As West Nile virus (WNV) can cause lethal diseases in raptors, a vaccination prophylaxis of free-living and captive populations is desirable. In the absence of vaccines approved for birds, equine vaccines have been used in falcons, but full protection against WNV infection was not achieved. Therefore, two DNA vaccines encoding the ectodomain of the envelope protein of WNV lineages 1 and 2, respectively, were evaluated in 28 large falcons. Four different vaccination protocols were used, including electroporation and booster-injections of recombinant WNV domain III protein, before challenge with the live WNV lineage 1 strain NY99. Drug safety, plasmid shedding and antibody production were monitored during the vaccination period. Serological, virological, histological, immunohistochemical and molecular biological investigations were performed during the challenge trials. Antibody response following vaccination was low overall and lasted for a maximum of three weeks. Plasmid shedding was not detected at any time. Viremia, mortality and levels, but not duration, of oral virus shedding were reduced in all of the groups during the challenge trial compared to the non-vaccinated control group. Likewise, clinical scoring, levels of cloacal virus shedding and viral load in organs were significantly reduced in three vaccination groups. Histopathological findings associated with WNV infections (meningo-encephalitis, myocarditis, and arteritis) were present in all groups, but immunohistochemical detection of the viral antigen was reduced. In conclusion, the vaccines can be used safely in falcons to reduce mortality and clinical signs and to lower the risk of virus transmission due to decreased levels of virus shedding and viremia, but full protection was not achieved in all groups.     

Bulk Carbohydrate Grain Filling of Barley β‐Glucan Mutants Studied by 1H HR MAS NMR

Temporal and genotypic differences in bulk carbohydrate accumulation in three barley genotypes differing in the content of mixed linkage β‐(1→3),(1→4)‐D‐glucan (β‐glucan) and starch were investigated using proton high‐resolution, magic angle spinning, nuclear magnetic resonance (¹H HR MAS NMR) during grain filling. For the first time, ¹H HR MAS NMR spectra of flour from immature barley seeds are analyzed. Spectral assignments are made using two‐dimensional (2D) NMR methods. Both α‐ and β‐glucan biosynthesis were characterized by inspection of the spectra as well as by calibration to the reference methods for starch and β‐glucan content. Starch was quantified with very good calibrations to the α‐(1→4) peak (5.29–5.40 ppm) and the region 3.67–3.83 ppm covering starch glycopyranosidic protons from H5 and H6. In contrast, the spectral inspection of the β‐anomeric region 4.45–4.85 ppm showed unexpected lack of intensity in the high β‐glucan mutant lys5f at seed maturity, resulting in poor calibration to reference β‐glucan content. We hypothesize that the lack of β‐glucan signal in lys5f indicates partial immobilization of the β‐glucan that appears to be either genotypic dependent or water/β‐glucan ratio dependent.     

Immunophysiology of Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus (Mitchill), and the relationship to parasitic copepod, Dichelesthium oblongum (Abilgaard) infection

The copepod parasite, Dichelesthium oblongum, is known to infect the Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus, within the area near New York city, USA, known as the NY Bight. The gross pathology associated with the juvenile and adult copepod stages along with the parasite's link in causing changes in sturgeon osmoregulatory capabilities has led us to investigate the host immunophysiology in relation to this host-parasite system. All the host variables, which included gill Na(+) -K(+) -ATPase activity, serum alkaline phosphatase (AP) and white blood cell differential counts, were affected in a non-linear manner by the copepod parasite. The parasites increased the host gill Na(+) -K(+) -ATPase activity and serum AP along with the percentage granulocytes while decreasing the percentage lymphocytes. A new method, developed to sample and preserve white blood cells in the field for future flow cytometry analysis, proved adequate. The effects of fish size, location and time of sampling were accounted for by the use of generalized linear models, and their effects on the host variables are discussed.     

Ozone loss inside the northern polar vortex during the 1991-1992 winter

Measurements made in the outer ring of the northern polar vortex from October 1991 through March 1992 reveal an altitude-dependent change in ozone, with a decrease at the bottom of the vortex and a substantial increase at the highest altitudes accessible to measurement. The increase is the result of ozone-rich air entering the vortex, and the decrease reflects ozone loss accumulated after the descent of the air through high concentrations of reactive chlorine. The depleted air that is released out of the bottom of the vortex is sufficient to significantly reduce column ozone at mid-latitudes.     

Complementary studies detecting classical bovine spongiform encephalopathy infectivity in jejunum,ileum and ileocaecal junction in incubating cattle

Recently we have described the distribution of bovine spongiform encephalopathy (BSE) infectivity and/or PrP^Sc in Peyer’s patches (PP) of the small intestine of orally BSE infected cattle. In this follow-up study additional jejunal and ileal PP’s and ileocaecal-junction tissue samples from 1, 4, and 24 months post infection (mpi) were examined by mouse (Tgbov XV) bioassay. Infectivity was demonstrated in ileal PP’s 4 mpi and the distribution/extent of infectivity at 24 mpi was comparable to those seen at earlier time points, revealing no indication for a decline/clearance. These data are relevant for the definition of Specified Risk Materials in the context of the TSE legislation worldwide.     

Impact of co-infection with Lepeophtheirus salmonis and Moritella viscosa on inflammatory and immune responses of Atlantic salmon (Salmo salar)

This study was conducted to determine the effects of a co-infection with Moritella viscosa at different exposure levels of sea lice Lepeophtheirus salmonis in Atlantic salmon (Salmo salar). M. viscosa (1.14 × 10⁶ cfu/ml) was introduced to all experimental tanks at 10 days post-lice infection (dpLs). Mean lice counts decreased over time in both the medium lice co-infection (31.5 ± 19.0 at 7 dpLs; 16.9 ± 9.3 at 46 dpLs) and high lice co-infection (62.0 ± 10.8 at 7 dpLs; 37.6 ± 11.3 at 46 dpLs). There were significantly higher mortalities and more severe skin lesions in the high lice co-infected group compared to medium lice co-infected group or M. viscosa-only infection. Quantitative gene expression analysis detected a significant upregulation of genes in skin from the high lice co-infection group consistent with severe inflammation (il-8, mmp-9, hep, saa). Skin lesions retrieved throughout the study were positive for M. viscosa growth, but these were rarely located in regions associated with lice. These results suggest that while M. viscosa infection itself may induce skin lesion development in salmon, co-infection with high numbers of lice can enhance this impact and significantly reduce the ability of these lesions to resolve, resulting in increased mortality.