Use of spray-dried blood meal as an alternative protein source in pirarucu (arapaima gigas) diets

We evaluated the effects of various dietary blood meal levels on the growth performance and body composition of pirarucu (Araipama gigas) juveniles. Fish (8.5 ± 0.4 g) were stocked into 24 tanks and fed for 60 days with eight isoproteic diets, having 0% to 21% incorporation of blood meal. Fish increased weight by six to 15 times from their initial weight. The highest body weights (117-135 g), growth rates (4%-5% BW/day), and protein retentions (19%-20%) were observed in fish fed 0% to 6% blood meal. Feed intake increased from 2.9% to 4.4% BW/day with increasing blood meal level. Feed conversion ratio (FCR: 1.0-1.1) did not vary among groups fed 0% to 6% blood meal (P < 0.001). However, when fish were fed more than 6% blood meal, FCR (1.3-1.7) and protein retention (11.1-13.7) deteriorated sharply. Lipid (7.7-11.7%) and energy (18.7-21.2 kJ/g) content increased with increasing blood meal levels up to 9%. © Taylor & Francis Group, LLC

Effects of dietary supplementation of Gracilaria sp. extracts on fillet quality, oxidative stress, and immune responses in European seabass (Dicentrarchus labrax)

The current study evaluated the effects of two different fractions derived from the methanolic extraction of the red seaweed Gracilaria sp. supplemented in European seabass (Dicentrarchus labrax) diets. With that purpose, three experimental diets were prepared: a basal diet (control), a control supplemented with the methanolic extract (GE, 0.5% diet) and a control supplemented with the insoluble residue of the GE extraction (GR, 4.5%). Seabass with an average initial weight of 16.5 ± 0.6 g were fed the experimental diets for 42 days, and the following parameters were evaluated: growth indicators, digestive enzyme activities, immune and oxidative stress responses, fillet pH and color (L*, a*, and b* values), and skin color. The dietary supplementation of GE or GR had no effect on growth performance, digestive enzyme activities, fillet pH, and color. Skin color was significantly lighter (L*) in fish-fed GE (83.9 ± 1.9) and GR (84.3 ± 2.3) diets when compared with the control group (81.9 ± 3.8). The dietary treatments did not affect the oxidative stress biomarkers. Alternative complement pathway (ACH50) was significantly higher in fish-fed GE diet (168.2 ± 13.4 EU mL−1) than in the control diet (113.1 ± 31.4 EU mL−1). No dietary effect was observed on peroxidase and lysozyme activities. The current study indicates that dietary supplementation of Gracilaria sp. methanolic extracts may have little influence on the innate immune system and skin color in seabass.</p

Dietary electrolyte balance affects growth performance, amylase activity and metabolic response in the meagre (Argyrosomus regius)

Dietary ion content is known to alter the acid-base balance in freshwater fish. The current study investigated the metabolic impact of acid-base disturbances produced by differences in dietary electrolyte balance (DEB) in the meagre (Argyrosomus regius), an euryhaline species. Changes in fish performance, gastric chyme characteristics, pH and ion concentrations in the bloodstream, digestive enzyme activities and metabolic rates were analyzed in meagre fed ad libitum two experimental diets (DEB 200 or DEB 700 mEq/kg) differing in the Na2CO3 content for 69 days. Fish fed the DEB 200 diet had 60–66% better growth performance than the DEB 700 group. Meagre consuming the DEB 200 diet were 90–96% more efficient than fish fed the DEB 700 diet at allocating energy from feed into somatic growth. The pH values in blood were significantly lower in the DEB 700 group 2 h after feeding when compared to DEB 200, indicating that acid-base balance in meagre was affected by electrolyte balance in diet. Osmolality, and Na+ and K+ concentrations in plasma did not vary with the dietary treatment. Gastric chyme in the DEB 700 group had higher pH values, dry matter, protein and energy contents, but lower lipid content than in the DEB 200 group. Twenty-four hours after feeding, amylase activity was higher in the gastrointestinal tract of DEB 700 group when compared to the DEB 200 group. DEB 700 group had lower routine metabolic (RMR) and standard metabolic (SMR) rates, indicating a decrease in maintenance energy expenditure 48 h after feeding the alkaline diet. The current study demonstrates that feeding meagre with an alkaline diet not only causes acid-base imbalance, but also negatively affects digestion and possibly nutrient assimilation, resulting in decreased growth performance.Fil: Magnoni, Leonardo Julián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentina. Terminal de Cruzeiros do Porto de Leixões; BrasilFil: Salas Leiton, Emilio. Terminal de Cruzeiros do Porto de Leixões; Brasil. IFAPA; EspañaFil: Peixoto, Maria João. Terminal de Cruzeiros do Porto de Leixões; Brasil. Universidad de Porto; PortugalFil: Pereira, Luis. Terminal de Cruzeiros do Porto de Leixões; BrasilFil: Silva Brito, Francisca. Terminal de Cruzeiros do Porto de Leixões; BrasilFil: Fontinha, Filipa. Terminal de Cruzeiros do Porto de Leixões; BrasilFil: Gonçalves, José F.M.. Terminal de Cruzeiros do Porto de Leixões; Brasil. Universidad de Porto; PortugalFil: Wilson, Jonathan M.. Terminal de Cruzeiros do Porto de Leixões; Brasil. Universidad de Porto; Portugal. Wilfrid Laurier University; CanadáFil: Schrama, Johan W.. University of Agriculture Wageningen; Países BajosFil: Ozório, Rodrigo O.A.. Terminal de Cruzeiros do Porto de Leixões; Brasil. Universidad de Porto; Portuga