RESUMONa presente pesquisa, avaliou-se o efeito da relação carbono/nitrogênio (C:N), na qualidade da água, produtividade e composição centesimal dos alevinos de Oreochromis niloticus durante 58 dias de cultivo. O desenho experimental consistiu em quatro tratamentos: um sistema convencional (controle) e três sistemas de biofloco (CN10, CN15 e CN20). Foram utilizadas 12 unidades experimentais de 0,04 m 3 , com 30 peixes (750 peixes m -3 ) com peso médio individual de 1,55±0,01 g. Verificou-se a existência de interação entre os parâmetros de qualidade da água do sistema de biofloco e os parâmetros produtivos dos alevinos de tilapia. O tratamento CN10 apresentou uma baixa produção de sólidos sedimentáveis, 38,61±0,54 mL L -1 (p<0,05), fato esse que contribuiu para o rápido crescimento dos indivíduos (21,7±2,18 g), atingindo uma produtividade final média de 15,50±0,81 kg m -3 (p<0,05). É possível concluir que o cultivo de alevinos de O. niloticus no sistema biofloco, com uma relação C:N de 10, apresentou o melhor rendimento de produção quando comparado aos outros tratamentos (CN15 e CN20).Palavras-chave: peixe, qualidade da água, crescimento, biofloco, proteína RESUMENEn la presente investigación se evaluó el efecto de la relación carbono/nitrógeno (C:N), la calidad del agua, la productividad y la composición proximal de alevines de Oreochromis niloticus durante 58 días de cultivo. El diseño experimental consistió de cuatro tratamientos: un sistema convencional (control) y tres sistemas biofloc (CN10, CN15 y CN20). Se utilizaron 12 unidades experimentales de 0.04 m 3 , con 30 peces (750 pez m -3 ) con peso promedio individual de 1.55±0.01 g. Se constató la existencia de interacción entre los parámetros de calidad de agua del sistema biofloc y los parámetros productivos de los alevines de tilapia. El tratamiento CN10 presentó una baja producción de sólidos sedimentables 38.61±0.54 mL L -1 (p<0.05), hecho que contribuyó con el rápido crecimiento de los individuos (21.7±2.18 g), alcanzando rendimientos finales promedios de 15.50±0.81 kg m -3 (p<0.05). Es posible concluir que el cultivo de alevinos de O. niloticus en sistema biofloc, con una relación C:N de 10, presentó el mejor rendimiento de producción si comparado con los otros tratamientos (CN15 y CN20).

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This study was conducted to determine whether the macroalgae Ulva papenfussi and Ulva nematoidea could be alternatives for preventing Litopenaeus vannamei vibriosis caused by the bacterium Vibrio parahaemolyticus. Phytochemical screening was performed on methanolic extracts to qualitatively determine the main groups of bioactive compounds, previous to an in vitro antibacterial test against V. parahaemolitycus. Phenols, polyphenols, flavonoids, and the high presence of carbohydrates were found in both macroalgae. U. papenfussi showed more presence of lipids and alkaloids than U. nematoidea . Macroalgae extracts prepared (v:v) with a 1:1 methanol: dichloromethane solvent was used for the in vitro test using the disc diffusion method (MDD). Filter paper discs impregnated with 1.0, 1.5, 2.0, 3.0, and 4.0 mg of the extracts showed antibacterial activity against V. Parahaemolitycus in a dose-dependent manner in both macroalgae. The inhibition zone varied significantly ( p < 0.05) from 8.33 ± 0.12 to 11.41 ± 0.73 mm for 1 to 3 mg of extract levels, respectively. In conclusion, both macroalgae have antibacterial activity in their crude extracts against this bacteria. It is suggested to evaluate it as a feed additive for L. vannamei. This study is the first report on a phytochemical screening and antibacterial activity of these macroalgae against V. parahaemolyticus.

Aim of study: To evaluate a green seaweed meal in the diets of Penaeus vannamei juveniles, comprising Ulva spp., Caulerpa spp. and Enteromorpha spp. as a feed blend at inclusion levels at 4% and 8%. Area of study: Universidad Nacional Agraria La Molina, Lima, Perú. Material and methods: Analyses were conducted to determine the pellet quality through percentages of dry matter retention (DMR), protein loss and water absorption capacity; and to evaluate the effect of this seaweed meal in the digestibility and zootechnical shrimp performance. Three treatments (diets) were formulated to contain 0% (control diet), 4% (M4) and 8% (M8 of green seaweed meals (blend)), in isonitrogenous (crude protein; 300 g kg-1) and isocaloric (3.3 Mcal kg-1) diets. The shrimps were reared at a density of 286 juveniles m-3 for 29 days in a recirculating aquaculture system (RAS). Main results: Among the diets, M4 had the highest DMR value (97.06%), whereas M8 had highest water absorption capacity (185.48%) with lower % of protein loss between the treatments diets. No differences were observed in the zootechnical performance, except for survival (p<0.05), with the M8 diet having highest mortality rate (44.4%) between the treatments diets. Research highlights: Incorporating 4% green seaweed meal in shrimp feed supported adequate growth and survival of juvenile P. vannamei with adequate DMR values, water absorption capacity, protein loss and high apparent dry matter digestibility and apparent digestibility of the reference diet.