Effects of dietary scallop and squid hydrolysates on growth of European seabass, Dicentrarchus labrax; California yellowtail, Seriola lalandi; and barramundi, Lates calcarifer

Squid processing byproducts and scallop viscera were homogenized and subjected to hydrolysis at 55 degrees C for 1.5 hr, followed by pasteurization at 75 degrees C for 30 min. The respective hydrolysates were incorporated into diets in which 30-70% of fishmeal (FM) was replaced with soybean meal (SBM) and evaluated as is (wet), dried, or impregnated into SBM for their effects on growth of European seabass, Dicentrarchus labrax; California yellowtail, Seriola lalandi; and barramundi, Lates calcarifer, in a series of 8-week experiments. No adverse thermal deterioration in the quality of hydrolysate occurred because of drum drying, compared to the wet hydrolysate. No differences were observed in growth of California yellowtail between SBM mixed with dry hydrolysate and SBM impregnated with wet hydrolysate. Dietary inclusion of hydrolysate improved feed attractability and growth and was beneficial in the early juvenile stage but not in the growout stage for European seabass and California yellowtail. However, in barramundi, no discernable benefit was observed from the addition of hydrolysates. The improved feed attractability and growth appear to be dependent on species and type of hydrolysate. The texture of fillets of yellowtail fed 70% FM replacement with SBM + squid hydrolysate diets was significantly firmer than without squid hydrolysate.