Abstract In the present study, the use of the microalgae Arthrospira sp., Chlorella sp., Isochrysis sp., and Nannochloropsis sp., as partial constituents in diets for Nile tilapia (Oreochromis niloticus), was evaluated in static tanks in a 53-day study, with a commercial diet containing 45% crude protein as a control treatment. Then, we replaced 25% of this diet with meals derived from each of the four microalgae species. Analysis of variance was employed to evaluate fish growth performance. Fish fed the diets with the microalgae Arthrospira sp. and Chlorella sp. had growth performance comparable to that of fish fed the control diet, as evaluated by growth parameters, such as final weight, weight gain, and percent weight gain, among others. In contrast, growth of fish receiving the microalgae Isochrysis sp. and Nannochloropsis sp. was significantly lower. Results of the present study indicate that the use of 25% of Arthrospira sp. and Chlorella sp. meals incorporated into the diet of O. niloticus does not compromise fish development, although there seems to be an opportunity for a further increment of the replacement level.

Resumen El presente estudio evaluó el uso de las microalgas Arthrospira sp., Chlorella sp., Isochrysis sp. y Nannochloropsis sp. como constituyentes parciales del alimento balanceado para tilapia del Nilo ( Oreochromis niloticus ) bajo condiciones de cultivo estático en un estudio de 53 días de duración. Un alimento balanceado comercial con contenido de proteína cruda de 45% se utilizó como dieta control, mismo que se molió finamente y se reconstituyó incorporando, a un nivel de inclusión de 25% de la dieta, las harinas de las cuatro especies de microalgas mencionadas. Se analizaron parámetros de producción de tilapia, incluyendo índices de crecimiento y supervivencia, mediante análisis de varianza. Los índices de crecimiento, tales como peso final, peso ganado y porcentaje de peso ganado de los peces alimentados con las microalgas Arthrospira sp. y Chlorella sp., así como la supervivencia, fueron similares a los de aquellos que recibieron la dieta control, mientras que el crecimiento de peces alimentados con las microalgas Isochrysis sp. y Nannochloropsis sp. fue inferior estadísticamente. Estos resultados indican que Arthrospira sp. y Chlorella sp. pueden ser incorporadas a un nivel de 25% del alimento balanceado sin afectar significativamente el crecimiento o la supervivencia de O. niloticus.

The marine bioprocessing industry offers great potential to utilize byproducts for fish meal replacement in aquafeeds. Jumbo squid is an important fishery commodity in Mexico, but only the mantle is marketed. Head, fins, guts and tentacles are discarded in spite of being protein-rich byproducts. This study evaluated the use of two jumbo squid byproduct hydrolysates obtained by acid-enzymatic hydrolysis (AEH) and by autohydrolysis (AH) as ingredients in practical diets for shrimp. The hydrolysates were included at levels of 2.5 and 5.0% of the diet dry weight in four practical diets, including a control diet without hydrolysate. Shrimp growth and survival were not significantly affected by the dietary treatments. Postharvest quality of abdominal muscle was evaluated in terms of proximate composition and sensory evaluation. Significantly higher crude protein was observed in the muscle of shrimp fed the highest hydrolysate levels, AH 5% (204.8 g kg- 1) or AEH 5% (201.3 g kg- 1). Sensory analysis of cooked muscle showed significant differences for all variables evaluated: color, odor, flavor, and firmness. It was concluded that Jumbo squid byproducts can be successfully processed by autohydrolysis or acid-enzymatic hydrolysis, and that up to 5.0% of the hydrolysates can be incorporated into shrimp diets without affecting growth or survival.