Evidence of a growth factor in some crustacean-based feed ingredients in diets for the giant tiger shrimp Penaeus monodon

Abstract: The essentiality of marine invertebrate meals in diets for marine shrimp is unresolved. Three experiments were carried out with juvenile Penaeus monodon of 3–6 g initial weight to address this issue. In a 6-week growth experiment, shrimp head meal (SHM) or whole dried krill Euphausia spp. were included in a basal diet at 5% increments from 0 to 15% without altering the gross nutritional specification of the diet and fed to five tank replicates of shrimp. Shrimp daily growth coefficient (DGC) improved curvilinearly (P <0.05) from 0.95% per day for the basal to 1.66 and 1.68% per day for the 15% SHM and 15% krill diets respectively. The same SHM and krill meals were extracted with phosphate-buffered saline (PBS) and the recovered insoluble and soluble fractions compared with the original meals when incorporated into a basal diet at rates equivalent to 20% of the original (Experiment 2). Diets were fed to six tank replicates of shrimp for 2 weeks. DGCs of shrimp fed diets with krill and the krill PBS-insoluble fraction were identical (1.34% per day) and better than the krill PBS-soluble fraction (1.10% per day), SHM (1.15% per day) and both PBS-insoluble and -soluble SHM fractions (1.14 and 1.19% per day); all of these diets were better than the basal diet (0.92% per day). In Experiment 3, fresh shrimp waste was freeze-dried (SW) and then sequentially fractionated using PBS, followed by 6 M urea with subsequent dialysis and affinity chromatography, to produce three soluble fractions (PBS-soluble and PBS/urea soluble dialysed material of >3.5 kDa or <3.5 kDa) and an insoluble PBS/urea fraction. These fractions, individually, and when combined together, and the intact SW, were incorporated into a basal diet at amounts equivalent to 20% of the original product and evaluated against a commercial Marsupenaeus japonicus shrimp feed when fed to six tank replicates of shrimp in a 2-week experiment. The M. japonicus feed gave the best DGC (2.57% per day), and better than the SW diet (1.19% per day) which, with the diet containing the insoluble fraction (1.05% per day), were the only diets significantly better than the basal diet (0.79% per day). It is concluded that these crustacean meals contained a growth factor, which was present predominantly in the insoluble protein constituent of the meal. [Copyright &y& Elsevier]