DIETARY ARGININE REQUIREMENT OF EARLY JUVENILE LARGEMOUTH BASS Micropterus salmoides

Farmed largemouth bass (LMB), Micropterus salmoides, is increasingly becoming an important food fish for consumers in the United States. Under farm conditions, LMB are fed diets high in protein content (> 40%), but the quantitative requirement for essential amino acids (AAs) are largely unknown for this North American species. Therefore, the objective of this study was to determine the quantitative requirement for arginine (Arg) in the diet of early juvenile LMB.

A basal diet was formulated to contain 0.82% Arg and the overall AA concentration [all derived from fishmeal (20% inclusion) and crystalline AAs] of a 40% crude protein LMB muscle, and 12% lipid. An additive supplementation of L-Arg to the basal diet was performed producing five additional diets containing Arg from 1.14 to 2.82%. Each diet was randomly assigned to triplicate groups of 15 early juvenile LMB [average initial weight (IW) of 9.6 ± 0.7g] stocked in an 18-aquaria recirculating aquaculture system. Fish in each aquarium were fed twice daily to apparent satiation for 8 weeks.

At the end of study, LMB in each aquarium were counted and group-weighed for the computation of performance parameters. No significant (P<0.05) differences in fish survival (ranging from 82 to 96%) were found among treatments. Based on quadratic broken-line regression analyses, the Arg requirement for optimizing thermal growth coefficient, weight gain (percent of initial), and feed efficiency of LMB was determined to be 2.2, 1.9, and 1.8% of the diet, respectively. Our results expand on the very limited knowledge of amino acid requirements for LMB and aid in the development of nutritious, environmental friendly and cost-effective diets for aquaculture enterprises.