Influence of temperature on protein utilization in juvenile European seabass (Dicentrarchus labrax)

The aim of this trial was to study the utilization of dietary protein by seabass juveniles with 5.5 g mean body weight, at two water temperatures: 18°C and 25°C. For that purpose, the fish were fed for 12 weeks, four isoenergetic diets with different protein levels (36, 42, 48, and 56%). At the end of the trial, growth rate and feed utilization were significantly better at the higher water temperature. Within each temperature, specific growth rate and feed efficiency were significantly higher with the 48 and 56% protein diets than with the other diets. At 25°C, feed efficiency was also significantly better with the 56% than with the 48% protein diet. N retention (g kg average body weight⁻¹ day⁻¹) was higher at 25°C than at 18°C but, as a % N intake the inverse was true. Although at 25°C N retention (% N intake) was not different among groups, retention in g kg ABW⁻¹ day⁻¹ was significantly higher with the 56% protein diet than with 36 and 42% protein diets. On the contrary, at 18°C N retention (g kg ABW⁻¹ day⁻¹) was similar among groups while as a percentage of N intake it was inversely related to the dietary protein level. Regarding energy utilization, at each temperature, there were no differences among dietary treatments on energy retention (g kg ABW⁻¹ day⁻¹). As a % of energy intake, energy retention significantly increased with the increase of dietary protein level at 25°C, while at 18°C, there were no significant differences among groups. Within each temperature, at the end of the trial, there were no differences among groups in proximate composition of whole fish. Apparent digestibility coefficients of dry matter, protein and energy significantly improved with the increase of water temperature but, within each temperature, there were no significant differences among groups. The results of this study indicate that, regardless of water temperature, the dietary protein requirement for growth seems to be satisfied with a diet containing 48% protein. Growth and feed efficiency were significantly higher at the higher temperature, however, protein utilization was more efficient at the lower temperature.     

The importance of environment and life stage on interpretation of silky shark relative abundance indices for the equatorial Pacific Ocean

Recent large fluctuations in an index of relative abundance for the silky shark in the eastern Pacific Ocean have called into question its reliability as a population indicator for management. To investigate whether these fluctuations were driven by environmental forcing rather than true changes in abundance, a Pacific‐wide approach was taken. Data collected by observers aboard purse‐seine vessels fishing in the equatorial Pacific were used to compute standardized trends in relative abundance by region, and where possible, by shark size category as a proxy for life stage. These indices were compared to the Pacific Decadal Oscillation (PDO), an index of Pacific Ocean climate variability. Correlation between silky indices and the PDO was found to differ by region and size category. The highest correlations by shark size category were for small (<90 cm total length [TL]) and medium (90–150 cm TL) sharks from the western region of the equatorial eastern Pacific (EP) and from the equatorial western Pacific. This correlation disappeared in the inshore EP. Throughout, correlations with the PDO were generally lower for large silky sharks (>150 cm TL). These results are suggestive of changes in the small and medium silky indices being driven by movement of juvenile silky sharks across the Pacific as the eastern edge of the Indo‐Pacific Warm Pool shifts location with ENSO events. Lower correlation of the PDO with large shark indices may indicate that those indices were less influenced by environmental forcing and therefore potentially less biased with respect to monitoring population trends.     

Functional Feeds to Tackle Meagre (Argyrosomus regius) Stress: Physiological Responses under Acute Stressful Handling Conditions

Marine algae are recognised sources of bioactive compounds that have attracted great interest as nutritional supplements for aquaculture fish. Intensive rearing conditions often expose fish to husbandry-related stressors, rendering fish more susceptible to disease and reducing production yields. The present work evaluated the potential of two marine algae extracts (Fucus vesiculosus and Nannochloropsis gaditana) as nutritional supplements to mitigate stress effects in meagre (Argyrosomus regius) exposed to an acute handling stress (AS). A plant-based diet was used as a control, and three other diets were prepared, which were similar to the control diet but supplemented with 1% of each algal extract or a combination of the two extracts (0.5% each). The effects of supplemented diets on stress biomarkers, antioxidant enzyme activities, and immune response were analysed in fish exposed to AS after 4 weeks of feeding. Supplemented diets did not affect growth performance but the inclusion of F. vesiculosus promoted higher feed efficiency, as compared to the control group. Dietary algal extracts supplementation reduced plasma glucose levels, increased white blood cell counts, and reduced the expression of pro-inflammatory genes when compared with the control. N. gaditana supplementation led to a reduction in hepatic antioxidant enzyme activity and glutathione levels, while F. vesiculosus supplementation increased muscle glutathione reductase activity and reduced lipid peroxidation. These findings support the potential of algal extracts as nutraceuticals in aquafeeds to enhance the ability of fish to cope with husbandry-related stressful conditions and ultimately improve fish health and welfare.     

Pharmacokinetic study of enrofloxacin in Nile tilapia (Oreochromis niloticus) after a single oral administration in medicated feed

The objective of this study was to evaluate the disposition kinetics of enrofloxacin (ENR) in the plasma and its distribution in the muscle tissue of Nile tilapia (Oreochromis niloticus) after a single oral dose of 10 mg/kg body weight via medicated feed. The fish were kept at a temperature between 28 and 30 °C. The collection period was between 30 min and 120 h after administration of the drug. The samples were analyzed by high‐performance liquid chromatography with a fluorescence detector (HPLC‐FLD). The ENR was slowly absorbed and eliminated from the plasma (C_max = 1.24 ± 0.37 μg/mL; T_max = 8 h; T_1/2Ke = 19.36 h). ENR was efficiently distributed in the muscle tissue and reached maximum values (2.17 ± 0.74 μg/g) after 8 h. Its metabolite, ciprofloxacin (CIP), was detected and quantified in the plasma (0.004 ± 0.005 μg/mL) and muscle (0.01 ± 0.011 μg/g) for up to 48 h. After oral administration, the mean concentration of ENR in the plasma was well above the minimum inhibitory concentrations (MIC₅₀) for most bacteria already isolated from fish except for Streptococcus spp. This way the dose used in this study allowed for concentrations in the blood to treat the diseases of tilapia.     

The role of silicon fertilization in the synthesis of phenolic compounds on chestnut plants infected with P. cinnamomi and C. parasitica

Journal of Plant Diseases and Protection - Silicon is considered a beneficial nutrient for agricultural crops by conferred protection against diseases. The antifungal effect of the phenolic...     

Pathological changes in the bone marrow of dogs with leishmaniosis

Bone marrow aspiration smears from 15 dogs naturally infected with leishmania were evaluated. Three of the dogs showed no clinical signs, six had up to three clinical signs and six had more than three. The most common pathological features of the bone marrow were megakaryocytic dysplasia in 10 of the dogs, erythrophagocytosis in eight, erythroid dysplasia in two and emperipolesis in two. The megakaryocytic and erythroid dysplasia were probably related to an increased number of marrow macrophages producing high levels of tumour necrosis factor alpha and interferon gamma. Six of the dogs with clinical signs showed bone marrow dysplastic features and erythrophagocytosis, suggesting that leishmaniosis could be the unique cause of both conditions.