Aspects of nutrition of largemouth bass Micropterus salmoides, spotted bass Micropterus punctulatus and their F1 backcross hybrid (Micropterus punctulatus x Micropterus salmoides) x Micropterus salmoides [Teleostei: Centrarchidae]

The largemouth bass Micropterus salmoides whole body exogenic essential amino acid profile was used to define an ideal protein to base a standardized experimental formulated diet with menhaden fish meal and porcine gelatin in a ratio of 24:5. The base diet was modified to investigate feed intake, growth (length and weight), proximate composition, and feed and protein conversion ratios. Modifications involved energy, protein, moisture, and nutrient density. Short-term feed intake was not influenced by energy or protein alone, but did conserve dry matter intake over a range of dietary moisture levels of 10 to 75% as well as nutrient density (energy and protein) when diluted by as much as 50% with non-nutritive bulk (cellulose). Growth trials indicated an energy to protein ratio (E:P) of 9.6 kcal/g protein is optimal and that 360 g protein and 3393 kcal digestible energy/kg diet (same E:P) produced growth not significantly different from the maximum.; Feeding trials where juvenile F1 hybrid back-cross black bass Micropterus salmoides x (M. punctulatus x M. salmoides) were fed zebra danio Brachydanio rerio demonstrated gastric digestion and evacuation are distinct processes. In juvenile spotted bass M. punctulatus fed meals of one or two golden shiner Notemigonus crysoleucas, kinetics of gastric evacuation differed with meal size. A single shiner exhibited a pattern of gastric evacuation consistent with the exponential decay model while two shiners followed a linear model with a subsequent transition to an exponential decay model. Juvenile largemouth bass fed meals of live goldfish or a pelleted diet formulation displayed kinetics of gastric evacuation differing markedly as a function of meal type with goldfish initially following a linear model that transitioned into exponential decay while the pelleted diet followed an exponential decay model. Dry matter flux (DMF) associated with gastric evacuation was constant when the proportion of the residuum remaining decreased linearly with time and was curvilinear otherwise. The constantly variable DMF associated with the pelleted diet indicates regulation is not directly coupled to dry matter. Spotted bass fed fathead minnows Pimephales promelas, paper-shell crayfish Orconectes immunis, or a pelleted diet formulation exhibited qualitatively different gastric residua. The stratified gastric residuum of pellets had three distinct layers when interacting with the gastric design of the black bass which resulted in incompletely digested solids being evacuated first.