Evaluation of Different Feed Types and Feed Additives Aimed at Alleviating Pollution Associated with Carp-culture

Abstract

Two experiments were conducted to investigate the effect of full-fat soybean as an alternative protein source, and the effect of different feed types and feed additives on reduction of tolerance nitrogen and phosphorus (T-N, T-P) for carp, Cyprinus carpio culture. Two preparations of full-fat soybean feeds, steam and extruded pellets (SP and EP), and three kinds of feed additives, Bacillus toyoi, phytase, and sepiolite (magnesium silicate) were fed to carp. Carp fingerlings (initial body weight of 8.9 and 12.0g) were fed 5 and 7 kinds of experimental diets for 60 days at 23.5 and 23.7°C in Exps. I and II, respectively.
In Exp. I, fish fed the diet containing extruded full-fat soybean showed almost same feed performances as the control diet, suggesting that the test ingredient is a possible alternative protein source for carp, similar to defatted soybean meal. In Exp. II, a 57% reduction of TN was observed in the fish fed low protein EP containing full-fat soybean compared with a commercial diet. Phytase provided to be very effective in SP diet, achieving a drop of over 37% in T-P, compared to the values from usual commercial diets. Apart from this, it was found that sepiolite was an effective binder of the feed and feces as well, preventing leaching into the environmental water. On the other hand, the fish fed EP and B. toyoi supplemented SP enabled a cut in the fecalmass output. These results indicated that utilization of full-fat soybean, EP, and SP with feed additives such as B. toyoi, phytase, and sepiolite, are potential ways for reducing T-N and T-P in carp culture.