DIETARY LYSINE REQUIREMENT OF JUVENILE HYBRID STRIPED BASS (MORONE-CHRYSOPS X MORONE-SAXATILIS)

A feeding trial was conducted to determine the dietary lysine requirement of juvenile hybrid striped bass in brackish (8 ppt) water. Semipurified diets containing 35% crude protein from fish muscle and crystalline amino acids were supplemented with graded levels of lysine. HCl and analyzed to contain 1.14, 1.44, 1.71, 1.92, 2.15 and 2.37% lysine on a dry-matter basis. Each diet was fed to triplicate groups of juvenile hybrids (approximately 8 g initial weight) in aquaria for 9 weeks, after which blood samples were taken and analyzed for free lysine in plasma. Overt signs of lysine deficiency such as suppressed growth, feed efficiency and plasma free lysine were observed in fish fed the basal diet containing 1.14% lysine. Nonlinear least-squares regression analysis of weight gain and feed efficiency data indicated that hybrid striped bass has a minimum lysine requirement (+/- s.e. ) of 1.41 +/- 0.08% of dry diet (4.03% of dietary protein).