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A 16-week feeding experiment was conducting in an indoor recirculating aquaculture system (RAS) to determine the effects of dietary protein level on the growth and digestive protease activity in juvenile bluegills. Six isocaloric experimental diets were forumalted with 32%, 35%, 38%, 41%, 44%, and 47% levels of protein. Menhdaen fish meal was use as the sole protein source. Juvenile bluegills of 24.91 ± 0.50 g initial weight were distributed into 24 151 L tanks with 12 fish each. Each diet had four replications. Fish were fed to satiation three times a day by hand. At the termination, there no mortalities in fish fed 38% through 47% protein diet. Bluegill fed 38% or 47% protein diet had significant higher body weight gain and specific growth rate (SGR) than fish fed 32% or 35% [rotein diet. No significant differences (p>0.05) were found in weight gain, SGR, and FCR among the fish fed 38% or higher protein diets. Protein efficiency ratio decreased with increasing dietary protein level from 32% to 47%. Acid protease activity of complete digestive tract increased in trend with increasing dietary protein level from 32% to 47%. No significant differences were detected in the protease activity at different pH level among the treatments. The optimal dietary protein requirement for juvenile bluegill was about 38.3%.

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Aquaculture--Research, Bluegill--Feeding and feeds, Bluegill--Growth, Bluegill--Physiology


Aquaculture and Fisheries

The Effect of Dietary Protein Level on the Growth Performance and Digestive Protease Activity in Juvenile Bluegill (Lepomis macrochrius)