| Summary: | As aquaculture continues to expand, protein sources have become more costly and less available. Simultaneously, lipid-extracted algal meals (LEA) (co-products of bio-diesel production) are becoming increasingly available as alternative sources of energy are investigated. By integrating LEA into aquaculture diets, feed prices could be lowered and bio-diesel production would have an additional revenue stream. Three feeding trials each of 7 weeks duration were conducted to evaluate five different algal meals as partial replacements for fishmeal and soy protein concentrate in diets for juvenile red drum (Sciaenops ocellatus). Apparent digestibility coefficients (ADCs) for CP and energy in various LEAs also were determined with red drum and hybrid striped bass (HSB). In the first trial, whole algae meal and LEA derived from Navicula sp. replaced 5 or 10% of the crude protein (CP) in the reference diet. Weight gain, feed efficiency (FE), hepatosomatic index (HSI), as well as protein and energy retention were not significantly (P>0.05) affected by the dietary treatments. Algal inclusion significantly affected the ADCs of the various dietary treatments for dry matter, CP, and energy. The inclusion of ash in the form of diatomaceous earth improved digestibility of protein as well as weight gain, survival and FE. A second feeding trial evaluated LEA derived from Chlorella sp. processed at high temperatures, replacing 5, 10, 20, and 25% of the CP in the reference diet. Weight gain, FE, survival, and protein efficiency ratio (PER) were significantly reduced at substitution levels of 20 and 25%. The third feeding trial evaluated LEA derived from Nanochloropsis salina, replacing 5, 7.5, 10, and 15% of the CP in the reference diet. Weight gain, FE, survival, and PER were significantly affected by some dietary treatments, with the 15% substitution levels causing significant reductions in performance. Intraperitoneal fat ratio and whole-body lipids were significantly lower in the fish fed the 15% substitution diet. Based on ...
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