Document Type: Research Paper
Iranian Fisheries Science Research Institute, Agricultural Research Education and Extension Organzation (AREEO), Ahwaz, IRAN.
Department of Fisheries, Ferdowsi University of Mashhad, Khorasan Razavi, Iran
IRTA, Centre de Sant Carles de la Rápita (IRTA-SCR), Unitat de Cultius Experimentals, Crta. del Poble Nou Km 5.5, Sant Carles de la Rápita, Spain
The effect of dietary partial replacement of fish meal (FM) by soybean protein (SP) alone or in combination with lysine (Lys) and methionine (Met) supplementation were tested in a 60-days feeding trial for silvery-black porgy (Sparidentex hasta) juveniles. Seven isoproteic (ca. 50% crude protein) and isoenergetic (ca. 22.4 MJ/kg) diets were formulated in which 45% (SP45), 60% (SP60) and 75% (SP75) of FM protein were replaced by SP and the control diet (FM) was prepared with FM as the major source of protein. In SP45+, SP60+ and SP75+ diets, 45 to 75% of FM was replaced by SP with supplementing blends of Lys and Met (98% of purity). The activities of the trypsin, lipase and α-amylase were higher in fish fed SP diets with crystalline amino acids supplementation than in the other groups (P < 0.05). Fish fed SP75 and SP75+ diets had the lowest red blood cell count and hematocrit level (P < 0.05). The results of the current study indicated that anti-nutritional factors in a soy-protein based diet rather than lysine and methionine deficiencies may have adverse effects on digestive enzymes activities and health condition in silvery-black porgy juveniles.