THE EFFECTS OF DIETARY FERMENTED SOYBEAN MEAL ON THE GROWTH AND DIGESTIVE ABILITY OF SPOTTED HALIBUT, VERASPER VARIEGATUS

In this study, we conducted a 8-week feeding experiment to determine the optimum level of fermented soybean meal (FSBM, in replacement of the fishmeal) in the diet for spotted halibut, Verasper variegatus. The fishmeal and FSBM were used as the main protein sources, and fish oil and soybean oil were used as the lipid sources. The five isocaloric and isonitrogenous diets contained 0, 10%, 20%, 30% and 40% FSBM replacing 0, (Ⅰ) 9.81%, (Ⅱ) 19.63%, (Ⅲ) 29.44% (Ⅳ) and 39.26% (Ⅴ) fishmeal protein respectively. Each diet was randomly given to a triplicate of 15 fish (49.01.0 g) per tank in the indoor culture system. The results showed that (1) the feeding efficiency significantly decreased along with the increase in FSBM in the diet. The mean final body weight, the specific growth rate, and the feed intake of the fish fed with Diet Ⅰ and Ⅱ were significantly higher than those in the other groups (P0.05). (2) Higher FSBM level resulted in the increased whole-body moisture and ash contents, and led to reduced whole-body crude protein and crude lipid contents. (3) The activities of stomach protease and hepatopancreas lipase first decreased and then increased along with the increase in the dietary FSBM. The enzyme activities were significantly higher in the fish fed with Diet Ⅰ than those fed with Diet Ⅲ (P0.05), but there was no significant difference from Diet Ⅱ (P0.05). The activities of stomach lipase of the fish fed with Diet Ⅱ, Ⅲ and Ⅴ were significantly higher than those of the fish fed with Diet Ⅳ and Ⅴ (P0.05). The activity of intestine amylase first increased and then decreased along with the increase in the dietary FSBM. The fish fed with Diet Ⅲ had significantly higher enzyme activity than the fish fed with Diet Ⅰ (P0.05), but there was no significant difference from the fish fed with Diet Ⅱ (P0.05). There were no significant differences in the activities of other digestive enzymes including the intestine protease, the stomach amylase, and the intestine lipase (P0.05). (4) The height of the mucosal fold and the thickness of the mid-intestine were significantly larger in the fish fed with Diet I than the fish fed with other diets (P0.05). There was no significant difference in the thickness of the mucosa (P0.05). These results indicated that 10% FSBM in the diet may not have significant effects on the growth, the feed utilization, and the physical indicators of spotted halibut; moreover, excessive FSBM could result in poor growth performance.