Effects of replacement of menhaden fish meal protein by soybean meal protein supplemented with or without pre-coated L-methionine and L-lysine on growth performance and body composition of juvenile southern flounder Paralichthys lethostigma
Presentation
Overview
Overview
Description
To reduce cost in commercial fish feed industries, soybean meal is considered to be one of the most suitable and stable supplies of an alternative ingredient for replacing fish meal. However, there is no published information on utilization of soybean meal as an alternative protein source in the diets of southern flounder, a high-value marine finfish in the Atlantic coastal region of the U.S. Two feeding trials were conducted to study the effect of varying dietary levels of solvent-extracted soybean meal on the growth, survival and body composition of juvenile flounder. In trial 1, seven diets were formulated replacing menhaden fish meal protein by soybean meal protein at 0, 10, 20, 30, 40, 50 and 60% without supplementing amino acids. In trial 2, eight diets were formulated replacing fish meal protein by soybean meal protein at 0, 10, 20, 30, 40, 50, 60 and 70% and supplementing pre-coated crystalline L-methionine and L-lysine. In the test diets, L-methionine and L-lysine were supplemented to simulate the methionine and lysine level found in the 45% whole body protein of southern flounder. All diets contained 9% squid meal and 5% krill meal and were formulated to have the same crude protein (45%) and crude lipid levels (11%). Each of the test diets was fed two times a day to triplicate groups of southern flounder (avg. wt. ± SD = 0.61 ± 0.03 g for trial 1 and 1.63 ± 0.14 g for trial 2) to apparent satiation. Trials 1 and 2 were conducted for 6 weeks and 8 weeks, respectively. Fish were held in 75 L recirculating sea water tank at 15 fish per tank.
In trial 1 without supplementing amino acids, survival of southern flounder fed more than 40% replacement of fish meal protein was significantly lowered compared to the control diet (0% replacement), whereas in trial 2, replacing fish meal protein from 0 to 70% by soybean meal protein (with amino acid supplementation) did not produce a significant difference in survival among treatments. In both trials, percent body weight gain of southern flounder fed more than 40% replacement of fish meal protein was significantly lower than in fish fed the 0% replacement diet. Other parameters such as feed intake, feed conversion efficiency, protein efficiency ratios and whole body proximate compositions were also analyzed. Results indicated that without supplementing methionine and lysine, the optimum level of menhaden fish meal protein replacement by solvent extracted soybean meal protein in southern flounder was not more than 40%. Supplementation of crystalline L-methionine and L-lysine in the diets did not significantly improve growth performance and feed efficiency of southern flounder at soybean meal protein replacement levels for menhaden fish meal protein of more than 40%.
