Reducing dietary protein in pond production of hybrid striped bass - study shows a significant reduction is possible in digestible protein level in commercial diets

Authors: Rawles, Steven - Steve; Green, Bartholomew - Bart; McEntire, Matthew - Matt; GAYLORD, T. GIBSON - Us Fish And Wildlife Service; Barrows, Frederic

Submitted to: Global Aquaculture Advocate
Publication Type: Trade Journal
Publication Acceptance Date: 5/31/2018
Publication Date: 6/11/2018
Citation: Rawles, S.D., Green, B.W., McEntire, M.E., Gaylord, T., Barrows, F. 2018. Reducing dietary protein in pond production of hybrid striped bass - study shows a significant reduction is possible in digestible protein level in commercial diets. Global Aquaculture Advocate. 137.

Interpretive Summary: The current work was aimed at vetting previous results in pond production of market-size hybrid striped bass at commercial stocking densities to assess impacts on fish production and water quality. Diets were formulated to contain digestible protein levels ranging from 41% to 35% and 15% crude lipid. The trial was conducted during the hottest portion of the growing season when impacts of feeding have the greatest influence on pond water quality. The 6-month pond study conducted in quarter-acre ponds began with advanced fingerlings (approximately 1/4 lb per fish) in May 2013 and concluded with market sized fish in October 2013. Final fish size ranged from 448 +/- 24g (about 1b) to 1122 +/- 46g (about 2.5 lb) with food conversions ranging from 1.34-1.37 lbs of feed per pound of gain. Results suggest that digestible protein can be lowered from 41% to 35% by careful diet formulation while supplementing the first three limiting amino acids (Met, Lys Thr) without detrimental changes to body composition or nutrient retentions. Market size distributions, nutrient retention, and pond water quality dynamics in relation to test diets are also discussed.

Technical Abstract: In previous work, we demonstrated that diets containing 40% digestible protein (DP) (45% crude protein) and 18 %lipid supplemented with Met and Lys resulted in superior performance and nutrient retentions in hybrid striped bass compared to less energy-dense diets when rearing hybrid striped bass at temperatures similar to the summer growing period of the Southern U.S. The current work was aimed at vetting previous results in pond production of market-size HSB at commercial stocking densities to assess impacts on fish productions indices and water quality parameters. Diets were formulated to contain digestible protein levels ranging from 41% to 35% DP and 15% crude lipid.) The trial was conducted during the hottest portion of the growing season when impacts of feeding have the greatest influence on pond water quality. The 6-month pond (0.1 ha; 0.25 ac) study began with advanced juveniles (approximately 121 g) in May 2013 and concluded with market sized fish in October 2013. Final fish size ranged from 448 +/- 24g to 1122 +/- 46g with food conversions ranging from 1.34-1.37. Results suggest that DP can be lowered from 41% DP to 35% DP by careful diet formulation while supplementing the first three limiting amino acids (Met, Lys Thr) without detrimental changes to body composition or nutrient retentions. Market size distributions, nutrient retention, and pond water quality dynamics in relation to test diets are also discussed.