Protein, amino acid and energy utilisation of juvenile Yellowtail Kingfish (Seriola lalandi): quantifying abiotic influences

Two experiments were conducted to evaluate the effect of abiotic factors on the digestible nutrient and energy utilisation of juvenile Yellowtail Kingfish (YTK). Experiment 1 considered the effect of temperature at 15 degrees C or 24 degrees C. Experiment 2 considered the effect of dissolved oxygen (DO) at 60% or 100% saturation at 20 degrees C. Duplicate groups of YTK per feed treatment (initial body weight Experiment 1 = 187.2 +/- 0.4 g fish(-1); Experiment 2 = 220.9 +/- 2.35 g fish(-1)) were fed a commercial diet at one of five ration levels. Feeding levels ranged from a restricted ration, equivalent to approximately 10% of satiation feeding, through to maximal satiation feeding. Feed trials were run over 35-38 days. Growth and nutrient deposition, feed intake and diet digestibility were assessed to establish nutrient retention efficiencies and maintenance requirements. Temperature was shown to have a varying effect on utilisation responses in YTK with the magnitude of the response dependent on the nutrient examined. Maintenance requirements of all nutrients generally increased with increasing temperature. Low DO at 60% saturation negatively affected the nutrient and energy utilisation efficiencies in YTK with this response tending to be more pronounced with increasing nutrient and energy intake. However DO level did not significantly affect feed intake. This study provides insight into the effects of abiotic factors on the nutritional physiology of YTK. Data generated from this study can be used to improve feed models for YTK facilitating better feed management and feed formulation through greater understanding of the influence of abiotic conditions on nutrient demand and utilisation